Fertility

Fertility is the natural capability to produce offspring. As a measure, fertility rate is the number of offspring born per mating pair, individual or population. Fertility differs from fecundity, which is defined as the potential for reproduction (influenced by gamete production, fertilization and carrying a pregnancy to term). A lack of fertility is infertility while a lack of fecundity would be called sterility.

Human fertility depends on factors of nutrition, sexual behavior, consanguinity, culture, instinct, endocrinology, timing, economics, way of life, and emotions.

Demography

In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to produce which is termed fecundity.[1][2] While fertility can be measured, fecundity cannot be. Demographers measure the fertility rate in a variety of ways, which can be broadly broken into "period" measures and "cohort" measures. "Period" measures refer to a cross-section of the population in one year. "Cohort" data on the other hand, follows the same people over a period of decades. Both period and cohort measures are widely used.[3]

Period measures

  • Crude birth rate (CBR) - the number of live births in a given year per 1,000 people alive at the middle of that year. One disadvantage of this indicator is that it is influenced by the age structure of the population.
  • General fertility rate (GFR) - the number of births in a year divided by the number of women aged 15–44, times 1000. It focuses on the potential mothers only, and takes the age distribution into account.
  • Child-Woman Ratio (CWR) - the ratio of the number of children under 5 to the number of women 15–49, times 1000. It is especially useful in historical data as it does not require counting births. This measure is actually a hybrid, because it involves deaths as well as births. (That is, because of infant mortality some of the births are not included; and because of adult mortality, some of the women who gave birth are not counted either.)
  • Coale's Index of Fertility - a special device used in historical research

Cohort measures

  • Total fertility rate (TFR) - the total number of children a woman would bear during her lifetime if she were to experience the prevailing age-specific fertility rates of women. TFR equals the sum for all age groups of 5 times each ASFR rate.[4]
  • Gross Reproduction Rate (GRR) - the number of girl babies a synthetic cohort will have. It assumes that all of the baby girls will grow up and live to at least age 50.
  • Net Reproduction Rate (NRR) - the NRR starts with the GRR and adds the realistic assumption that some of the women will die before age 49; therefore they will not be alive to bear some of the potential babies that were counted in the GRR. NRR is always lower than GRR, but in countries where mortality is very low, almost all the baby girls grow up to be potential mothers, and the NRR is practically the same as GRR. In countries with high mortality, NRR can be as low as 70% of GRR. When NRR = 1.0, each generation of 1000 baby girls grows up and gives birth to exactly 1000 girls. When NRR is less than one, each generation is smaller than the previous one. When NRR is greater than 1 each generation is larger than the one before. NRR is a measure of the long-term future potential for growth, but it usually is different from the current population growth rate.

Social and economic determinants of fertility

A parent's number of children strongly correlates with the number of children that each person in the next generation will eventually have.[5] Factors generally associated with increased fertility include religiosity,[6] intention to have children,[7] and maternal support.[8] Factors generally associated with decreased fertility include wealth, education,[9] female labor participation,[10] urban residence,[11] intelligence, increased female age and (to a lesser degree) increased male age.

The "Three-step Analysis" of the fertility process was introduced by Kingsley Davis and Judith Blake in 1956 and makes use of three proximate determinants:[12][13] The economic analysis of fertility is part of household economics, a field that has grown out of the New Home Economics. Influential economic analyses of fertility include Becker (1960),[14] Mincer (1963),[15] and Easterlin (1969).[16] The latter developed the Easterlin hypothesis to account for the Baby Boom.

Bongaarts' model of components of fertility

Bongaarts proposed a model where the total fertility rate of a population can be calculated from four proximate determinants and the total fecundity (TF). The index of marriage (Cm), the index of contraception (Cc), the index of induced abortion (Ca) and the index of postpartum infecundability (Ci). These indices range from 0 to 1. The higher the index, the higher it will make the TFR, for example a population where there are no induced abortions would have a Ca of 1, but a country where everybody used infallible contraception would have a Cc of 0.

TFR = TF × Cm × Ci × Ca × Cc

These four indices can also be used to calculate the total marital fertility (TMFR) and the total natural fertility (TN).

TFR = TMFR × Cm

TMFR = TN × Cc × Ca

TN = TF × Ci

Intercourse
The first step is sexual intercourse, and an examination of the average age at first intercourse, the average frequency outside marriage, and the average frequency inside.
Conception
Certain physical conditions may make it impossible for a woman to conceive. This is called "involuntary infecundity." If the woman has a condition making it possible, but unlikely to conceive, this is termed "subfecundity." Venereal diseases (especially gonorrhea, syphilis, and chlamydia) are common causes. Nutrition is a factor as well: women with less than 20% body fat may be subfecund, a factor of concern for athletes and people susceptible to anorexia. Demographer Ruth Frisch has argued that "It takes 50,000 calories to make a baby". There is also subfecundity in the weeks following childbirth, and this can be prolonged for a year or more through breastfeeding. A furious political debate raged in the 1980s over the ethics of baby food companies marketing infant formula in developing countries. A large industry has developed to deal with subfecundity in women and men. An equally large industry has emerged to provide contraceptive devices designed to prevent conception. Their effectiveness in use varies. On average, 85% of married couples using no contraception will have a pregnancy in one year. The rate drops to the 20% range when using withdrawal, vaginal sponges, or spermicides. (This assumes the partners never forget to use the contraceptive.) The rate drops to only 2 or 3% when using the pill or an IUD, and drops to near 0% for implants and 0% for tubal ligation (sterilization) of the woman, or a vasectomy for the man.
Gestation
After a fetus is conceived, it may or may not survive to birth. "Involuntary fetal mortality" involves natural abortion, miscarriages and stillbirth (a fetus born dead). Human intervention intentionally causing abortion of the fetus is called "therapeutic abortion".

Fertility biology

Women have hormonal cycles which determine when they can achieve pregnancy. The cycle is approximately twenty-eight days long, with a fertile period of five days per cycle, but can deviate greatly from this norm. Men are fertile continuously, but their sperm quality is affected by their health, frequency of ejaculation, and environmental factors.

Fertility declines with age in both sexes. In women the decline is more rapid, with complete infertility normally occurring around the age of 50.

Pregnancy rates for sexual intercourse are highest when it is done every 1 or 2 days,[17] or every 2 or 3 days.[18] Studies have shown no significant difference between different sex positions and pregnancy rate, as long as it results in ejaculation into the vagina.[19]

Menstrual cycle

Pregnancy chance by day near ovulation
Chance of fertilization by menstrual cycle day relative to ovulation.[20]

A woman's menstrual cycle begins, as it has been arbitrarily assigned, with menses. Next is the follicular phase where estrogen levels build as an ovum matures (due to the follicular stimulating hormone, or FSH) within the ovary. When estrogen levels peak, it spurs a surge of luteinizing hormone (LH) which finishes the ovum and enables it to break through the ovary wall. This is ovulation. During the luteal phase, which follows ovulation LH and FSH cause the post-ovulation ovary to develop into the corpus luteum which produces progesterone. The production of progesterone inhibits the LH and FSH hormones which (in a cycle without pregnancy) causes the corpus luteum to atrophy, and menses to begin the cycle again.

Peak fertility occurs during just a few days of the cycle: usually two days before and two days after the ovulation date.[21] This fertile window varies from woman to woman, just as the ovulation date often varies from cycle to cycle for the same woman.[22] The ovule is usually capable of being fertilized for up to 48 hours after it is released from the ovary. Sperm survive inside the uterus between 48 and 72 hours on average, with the maximum being 120 hours (5 days).

These periods and intervals are important factors for couples using the rhythm method of contraception.

Female fertility

The average age of menarche in the United States is about 12.5 years.[23] In postmenarchal girls, about 80% of the cycles are anovulatory (ovulation does not actually take place) in the first year after menarche, 50% in the third and 10% in the sixth year.[24][25]

Menopause occurs during a woman's midlife (between ages 48 and 55).[26][27] During menopause, hormonal production by the ovaries is reduced, eventually causing a permanent cessation of the primary function of the ovaries, particularly the creation of the uterine lining (period). This is considered the end of the fertile phase of a woman's life.

The following effects of age and female fertility have been found in women trying to get pregnant, without using fertility drugs or in vitro fertilization:[28]

  • At age 30
    • 75% will have a conception ending in a live birth within one year
    • 91% will have a conception ending in a live birth within four years.
  • At age 35
    • 66% will have a conception ending in a live birth within one year
    • 84% will have a conception ending in a live birth within four years.
  • At age 40
    • 44% will have a conception ending in a live birth within one year
    • 64% will have a conception ending in a live birth within four years.

[28]

Studies of actual couples trying to conceive have come up with higher results: one 2004 study of 770 European women found that 82% of 35- to 39-year-old women conceived within a year,[29] while another in 2013 of 2,820 Danish women saw 78% of 35- to 40-year-olds conceive within a year.[30]

The use of fertility drugs and/or invitro fertilization can increase the chances of becoming pregnant at a later age.[31] Successful pregnancies facilitated by fertility treatment have been documented in women as old as 67.[32] Studies since 2004 now show that mammals may continue to produce new eggs throughout their lives, rather than being born with a finite number as previously thought. Researchers at the Massachusetts General Hospital in Boston, US, say that if eggs are newly created each month in humans as well, all current theories about the aging of the female reproductive system will have to be overhauled, although at this time this is simply conjecture.[33][34]

According to the March of Dimes, "about 9 percent of recognized pregnancies for women aged 20 to 24 ended in miscarriage. The risk rose to about 20 percent at age 35 to 39, and more than 50 percent by age 42".[35] Birth defects, especially those involving chromosome number and arrangement, also increase with the age of the mother. According to the March of Dimes, "At age 25, your risk of having a baby with Down syndrome is 1 in 1,340. At age 30, your risk is 1 in 940. At age 35, your risk is 1 in 353. At age 40, your risk is 1 in 85. At age 45, your risk is 1 in 35."[36]

Male fertility

Some research suggest that increased male age is associated with a decline in semen volume, sperm motility, and sperm morphology.[37] In studies that controlled for female age, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rates between 23% and 38%.[37] It is suggested that sperm count declines with age, with men aged 50–80 years producing sperm at an average rate of 75% compared with men aged 20–50 years and that larger differences are seen in how many of the seminiferous tubules in the testes contain mature sperm:[37]

  • In males 20–39 years old, 90% of the seminiferous tubules contain mature sperm.
  • In males 40–69 years old, 50% of the seminiferous tubules contain mature sperm.
  • In males 80 years old and older, 10% of the seminiferous tubules contain mature sperm.[38]

Decline in male fertility is influenced by many factors, including lifestyle, environment and psychological factors.[39]

Some research also suggests increased risks for health problems for children of older fathers, but no clear association has been proven.[40] A large scale in Israel study suggested that the children of men 40 or older were 5.75 times more likely than children of men under 30 to have an autism spectrum disorder, controlling for year of birth, socioeconomic status, and maternal age.[41] Increased paternal age is suggested by some to directly correlate to schizophrenia but it is not proven.[42][43][44][45][46]

Australian researchers have found evidence to suggest overweight obesity may cause subtle damage to sperm and prevent a healthy pregnancy. They say fertilization was 40% less likely to succeed when the father was overweight.[47]

The American Fertility Society recommends an age limit for sperm donors of 50 years or less,[48] and many fertility clinics in the United Kingdom will not accept donations from men over 40 or 45 years of age.[49]

Historical trends by country

France

The French pronatalist movement from 1919–1945 failed to convince French couples they had a patriotic duty to help increase their country's birthrate. Even the government was reluctant in its support to the movement. It was only between 1938 and 1939 that the French government became directly and permanently involved in the pronatalist effort. Although the birthrate started to surge in late 1941, the trend was not sustained. Falling birthrate once again became a major concern among demographers and government officials beginning in the 1970s.[50]

United States

From 1800 to 1940, fertility fell in the US. There was a marked decline in fertility in the early 1900s, associated with improved contraceptives, greater access to contraceptives and sexuality information and the "first" sexual revolution in the 1920s.

US Birth Rates
United States crude birth rate (births per 1000 population); Baby Boom years in red.[51]

Post-WWII

After 1940 fertility suddenly started going up again, reaching a new peak in 1957. After 1960, fertility started declining rapidly. In the Baby Boom years (1946–1964), women married earlier and had their babies sooner; the number of children born to mothers after age 35 did not increase.

Sexual revolution

After 1960, new methods of contraception became available, ideal family size fell, from 3 to 2 children. Couples postponed marriage and first births, and they sharply reduced the number of third and fourth births.

Infertility

Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term. There are many biological causes of infertility, including some that medical intervention can treat.[52]

See also

Footnotes

  1. ^ "The demography of fertility and infertility". www.gfmer.ch.
  2. ^ http://www.enotes.com/public-health-encyclopedia/fecundity-fertility
  3. ^ For detailed discussions of each measure see Paul George Demeny and Geoffrey McNicoll, Encyclopedia of Population (2003)
  4. ^ Another way of doing it is to add up the ASFR for age 10-14, 15-19, 20-24, etc., and multiply by 5 (to cover the 5 year interval).
  5. ^ Murphy, Michael (2013). "Cross-National Patterns of Intergenerational Continuities in Childbearing in Developed Countries". Biodemography and Social Biology. 59 (2): 101–126. doi:10.1080/19485565.2013.833779. ISSN 1948-5565. PMC 4160295. PMID 24215254.
  6. ^ Hayford, S. R.; Morgan, S. P. (2008). "Religiosity and Fertility in the United States: The Role of Fertility Intentions". Social Forces. 86 (3): 1163–1188. doi:10.1353/sof.0.0000. PMC 2723861. PMID 19672317.
  7. ^ Lars Dommermuth; Jane Klobas; Trude Lappegård (2014). "Differences in childbearing by time frame of fertility intention. A study using survey and register data from Norway". Part of the research project Family Dynamics, Fertility Choices and Family Policy (FAMDYN)
  8. ^ Schaffnit, S. B.; Sear, R. (2014). "Wealth modifies relationships between kin and women's fertility in high-income countries". Behavioral Ecology. 25 (4): 834–842. doi:10.1093/beheco/aru059. ISSN 1045-2249.
  9. ^ Rai, Piyush Kant; Pareek, Sarla; Joshi, Hemlata (2013). "Regression Analysis of Collinear Data using r-k Class Estimator: Socio-Economic and Demographic Factors Affecting the Total Fertility Rate (TFR) in India" (PDF). Journal of Data Science. 11.
  10. ^ Bloom, David; Canning, David; Fink, Günther; Finlay, Jocelyn (2009). "Fertility, female labor force participation, and the demographic dividend". Journal of Economic Growth. 14 (2): 79–101. doi:10.1007/s10887-009-9039-9.
  11. ^ Sato, Yasuhiro (30 July 2006), "Economic geography, fertility and migration" (PDF), Journal of Urban Economics, retrieved 31 March 2008
  12. ^ Bongaarts, John (1978). "A Framework for Analyzing the Proximate Determinants of Fertility". Population and Development Review. 4 (1): 105–132. doi:10.2307/1972149. JSTOR 1972149.
  13. ^ Stover, John (1998). "Revising the Proximate Determinants of Fertility Framework: What Have We Learned in the past 20 Years?". Studies in Family Planning. 29 (3): 255–267. doi:10.2307/172272. JSTOR 172272.
  14. ^ Becker, Gary S. 1960. "An Economic Analysis of Fertility." In National Bureau Committee for Economic Research, Demographic and Economic Change in Developed Countries, a Conference of the Universities. Princeton, N.J.: Princeton University Press
  15. ^ Mincer, Jacob. 1963. "Market Prices, Opportunity Costs, and Income Effects," in C. Christ (ed.) Measurement in Economics. Stanford, CA: Stanford University Press
  16. ^ Easterlin, Richard A. (1975). "An Economic Framework for Fertility Analysis". Studies in Family Planning. 6 (3): 54–63. doi:10.2307/1964934. JSTOR 1964934. PMID 1118873.
  17. ^ "How to get pregnant". Mayo Clinic. 2016-11-02. Retrieved 2018-02-16.
  18. ^ "Fertility problems: assessment and treatment, Clinical guideline [CG156]". National Institute for Health and Care Excellence. Retrieved 2018-02-16. Published date: February 2013. Last updated: September 2017
  19. ^ Dr. Philip B. Imler & David Wilbanks. "The Essential Guide to Getting Pregnant" (PDF). American Pregnancy Association.
  20. ^ Dunson, D.B.; Baird, D.D.; Wilcox, A.J.; Weinberg, C.R. (1999). "Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation". Human Reproduction. 14 (7): 1835–1839. doi:10.1093/humrep/14.7.1835. ISSN 1460-2350.
  21. ^ "Archived copy". Archived from the original on 2008-12-21. Retrieved 2008-09-22.CS1 maint: Archived copy as title (link)
  22. ^ Creinin, Mitchell D.; Keverline, Sharon; Meyn, Leslie A. (2004). "How regular is regular? An analysis of menstrual cycle regularity". Contraception. 70 (4): 289–92. doi:10.1016/j.contraception.2004.04.012. PMID 15451332.
  23. ^ Anderson, S. E.; Dallal, G. E.; Must, A. (2003). "Relative Weight and Race Influence Average Age at Menarche: Results From Two Nationally Representative Surveys of US Girls Studied 25 Years Apart". Pediatrics. 111 (4 Pt 1): 844–50. doi:10.1542/peds.111.4.844. PMID 12671122.
  24. ^ Apter D (February 1980). "Serum steroids and pituitary hormones in female puberty: a partly longitudinal study". Clin. Endocrinol. 12 (2): 107–20. doi:10.1111/j.1365-2265.1980.tb02125.x. PMID 6249519.
  25. ^ Apter, D (1980). "Serum steroids and pituitary hormones in female puberty: a partly longitudinal study". Clinical Endocrinology. 12 (2): 107–20. doi:10.1111/j.1365-2265.1980.tb02125.x. PMID 6249519.
  26. ^ Takahashi, TA; Johnson, KM (May 2015). "Menopause". The Medical Clinics of North America. 99 (3): 521–34. doi:10.1016/j.mcna.2015.01.006. PMID 25841598.
  27. ^ Bourgeois, F. John; Gehrig, Paola A.; Veljovich, Daniel S. (1 January 2005). Obstetrics and Gynecology Recall. Lippincott Williams & Wilkins. ISBN 9780781748797 – via Google Books.
  28. ^ a b A computer simulation run by Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research:
    • Leridon, H. (2004). "Can assisted reproduction technology compensate for the natural decline in fertility with age? A model assessment". Human Reproduction. 19 (7): 1548–53. doi:10.1093/humrep/deh304. PMID 15205397.
  29. ^ Dunson, David B.; Baird, Donna D.; Colombo, Bernardo (2004). "Increased Infertility With Age in Men and Women". Obstetrics & Gynecology. 103 (1): 51–6. doi:10.1097/01.AOG.0000100153.24061.45. PMID 14704244.
  30. ^ Rothman, Kenneth J.; Wise, Lauren A.; Sørensen, Henrik T.; Riis, Anders H.; Mikkelsen, Ellen M.; Hatch, Elizabeth E. (2013). "Volitional determinants and age-related decline in fecundability: a general population prospective cohort study in Denmark". Fertility and Sterility. 99 (7): 1958–64. doi:10.1016/j.fertnstert.2013.02.040. PMC 3672329. PMID 23517858.
  31. ^ Fertility Nutraceuticals, LLC "How to improve IVF success rates with smart fertility supplement strategy' May 6, 2014
  32. ^ "Spanish woman ' is oldest mother'". BBC News. 2006-12-30. Retrieved 2006-12-30.
  33. ^ Couzin, Jennifer (2004). "Reproductive Biology: Textbook Rewrite? Adult Mammals May Produce Eggs After All". Science. 303 (5664): 1593. doi:10.1126/science.303.5664.1593a. PMID 15016968.
  34. ^ Wallace, WH; Kelsey, TW (2010). "Human Ovarian Reserve from Conception to the Menopause". PLoS ONE. 5 (1): e8772. arXiv:1106.1382. Bibcode:2010PLoSO...5.8772W. doi:10.1371/journal.pone.0008772. PMC 2811725. PMID 20111701.
  35. ^ "Pregnancy After 35". March of Dimes. Retrieved October 30, 2014.
  36. ^ "Down syndrome".
  37. ^ a b c Kidd, Sharon A; Eskenazi, Brenda; Wyrobek, Andrew J (2001). "Effects of male age on semen quality and fertility: a review of the literature". Fertility and Sterility. 75 (2): 237–48. doi:10.1016/S0015-0282(00)01679-4. PMID 11172821.
  38. ^ Effect of Age on Male Fertility Seminars in Reproductive Endocrinology. Volume, Number 3, August 1991. Sherman J. Silber, M.D.
  39. ^ Campagne, Daniel M. (2013). "Can Male Fertility Be Improved Prior to Assisted Reproduction through The Control of Uncommonly Considered Factors?". International Journal of Fertility & Sterility. 6 (4): 214–23. PMC 3850314. PMID 24520443.
  40. ^ Wiener-Megnazi, Zofnat; Auslender, Ron; Dirnfeld, Martha (1 January 2012). "Advanced paternal age and reproductive outcome". Asian J Androl. 14 (1): 69–76. doi:10.1038/aja.2011.69. PMC 3735149. PMID 22157982.
  41. ^ Reichenberg, Abraham; Gross, Raz; Weiser, Mark; Bresnahan, Michealine; Silverman, Jeremy; Harlap, Susan; Rabinowitz, Jonathan; Shulman, Cory; Malaspina, Dolores; Lubin, Gad; Knobler, Haim Y.; Davidson, Michael; Susser, Ezra (2006). "Advancing Paternal Age and Autism". Archives of General Psychiatry. 63 (9): 1026–32. doi:10.1001/archpsyc.63.9.1026. PMID 16953005.
  42. ^ Jaffe, AE; Eaton, WW; Straub, RE; Marenco, S; Weinberger, DR (1 March 2014). "Paternal age, de novo mutations and schizophrenia". Mol Psychiatry. 19 (3): 274–275. doi:10.1038/mp.2013.76. PMC 3929531. PMID 23752248.
  43. ^ Schulz, S. Charles; Green, Michael F.; Nelson, Katharine J. (1 April 2016). Schizophrenia and Psychotic Spectrum Disorders. Oxford University Press. ISBN 9780199378074 – via Google Books.
  44. ^ Malaspina, Dolores; Harlap, Susan; Fennig, Shmuel; Heiman, Dov; Nahon, Daniella; Feldman, Dina; Susser, Ezra S. (2001). "Advancing Paternal Age and the Risk of Schizophrenia". Archives of General Psychiatry. 58 (4): 361–7. doi:10.1001/archpsyc.58.4.361. PMID 11296097.
  45. ^ Sipos, Attila; Rasmussen, Finn; Harrison, Glynn; Tynelius, Per; Lewis, Glyn; Leon, David A; Gunnell, David (2004). "Paternal age and schizophrenia: a population based cohort study". BMJ. 329 (7474): 1070. doi:10.1136/bmj.38243.672396.55. PMC 526116. PMID 15501901.
  46. ^ Malaspina, Dolores; Corcoran, Cheryl; Fahim, Cherine; Berman, Ariela; Harkavy-Friedman, Jill; Yale, Scott; Goetz, Deborah; Goetz, Raymond; Harlap, Susan; Gorman, Jack (2002). "Paternal age and sporadic schizophrenia: Evidence for de novo mutations". American Journal of Medical Genetics. 114 (3): 299–303. doi:10.1002/ajmg.1701. PMC 2982144. PMID 11920852.
  47. ^ "Obesity | Fat men linked to low fertility". Sydney Morning Herald. 18 October 2010. Retrieved 19 October 2010.
  48. ^ Plas, E; Berger, P; Hermann, M; Pflüger, H (2000). "Effects of aging on male fertility?". Experimental Gerontology. 35 (5): 543–51. doi:10.1016/S0531-5565(00)00120-0. PMID 10978677.
  49. ^ Age Limit of Sperm Donors in the United Kingdom Pdf file Archived October 3, 2008, at the Wayback Machine
  50. ^ Reggiani, Andrés Horacio (Spring 1996). "Procreating France: The Politics of Demography, 1919-1945". French Historical Studies. 19 (3): 725–54. doi:10.2307/286642. JSTOR 286642.
  51. ^ CDC Bottom of this page https://www.cdc.gov/nchs/products/vsus.htm "Vital Statistics of the United States, 2003, Volume I, Natality", Table 1-1 "Live births, birth rates, and fertility rates, by race: United States, 1909-2003."
  52. ^ Makar, Robert S.; Toth, Thomas L. (2002). "The Evaluation of Infertility". American Journal of Clinical Pathology. 117 Suppl: S95–103. doi:10.1309/w8lj-k377-dhra-cp0b. PMID 14569805.

References

This article incorporates material from the Citizendium article "Fertility (demography)", which is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License but not under the GFDL.

  • Barrett, Richard E., Donald J. Bogue, and Douglas L. Anderton. The Population of the United States 3rd Edition (1997) compendium of data
  • Campagne, Daniel M (2013). "Can Male Fertility Be Improved Prior to Assisted Reproduction through The Control of Uncommonly Considered Factors?". International Journal of Fertility & Sterility. 6 (4): 214–23. PMC 3850314. PMID 24520443.
  • Coale, Ansley J. and Susan C. Watkins, eds. The Decline of Fertility in Europe, (1986)
  • Eversley, D. E. C. Social Theories of Fertility and the Malthusian Debate (1959) online edition
  • Garrett, Eilidh ety al. Family Size in England and Wales: Place, Class, and Demography, 1891-1911(2001) online edition
  • Grabill, Wilson H.. Clyde V. Kiser, Pascal K. Whelpton. The Fertility of American Women (1958), influential study at the peak of the Baby Boom online edition
  • GuzmÁn, JosÉ Miguel et al. The Fertility Transition in Latin America (1996) online edition
  • Haines, Michael R. and Richard H. Steckel (eds.), A Population History of North America. Cambridge University Press, 2000, 752 pp. advanced scholarship
  • Hawes, Joseph M. and Elizabeth I. Nybakken, eds. American Families: a Research Guide and Historical Handbook. (Greenwood Press, 1991)
  • Klein, Herbert S. A Population History of the United States. Cambridge University Press, 2004. 316 pp
  • Knox, P. L. et al. The United States: A Contemporary Human Geography. Longman, 1988. 287 pp.
  • Kohler, Hans-Peter Fertility and Social Interaction: An Economic Perspective (2001) online edition
  • Leete, Richard. Dynamics of Values in Fertility Change (1999) online edition
  • Lovett, Laura L. Conceiving the Future: Pronatalism, Reproduction, and the Family in the United States, 1890–1938, (2007) 236 pages;
  • Mintz Steven and Susan Kellogg. Domestic Revolutions: a Social History of American Family Life. (1988)
  • Pampel, Fred C. and H. Elizabeth Peters, "The Easterlin Effect," Annual Review of Sociology (1995) v21 pp 163–194]
  • Population Reference Bureau, Population Handbook (5th ed. 2004) online (5th ed. 2004).
  • Reed, James. From Private Vice to Public Virtue: The Birth Control Movement and American Society Since 1830. 1978.
  • Tarver, James D. The Demography of Africa (1996) online edition
  • Weeks, John R. Population: An Introduction to Concepts and Issues (10th ed. 2007), standard textbook

Journals

Further reading

External links

Assisted reproductive technology

Assisted reproductive technology (ART) are medical procedures used primarily to address infertility. It includes procedures such as in vitro fertilization. It may include intracytoplasmic sperm injection (ICSI), cryopreservation of gametes or embryos, and/or may involve the use of fertility medication. When used to address infertility, it may also be referred to as fertility treatment. ART mainly belongs to the field of reproductive endocrinology and infertility. Some forms of ART are also used with regard to fertile couples for genetic reasons (preimplantation genetic diagnosis). ART may also be used in surrogacy arrangements, although not all surrogacy arrangements involve ART.

Birth control

Birth control, also known as contraception and fertility control, is a method or device used to prevent pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth control only became available in the 20th century. Planning, making available, and using birth control is called family planning. Some cultures limit or discourage access to birth control because they consider it to be morally, religiously, or politically undesirable.The most effective methods of birth control are sterilization by means of vasectomy in males and tubal ligation in females, intrauterine devices (IUDs), and implantable birth control. This is followed by a number of hormone-based methods including oral pills, patches, vaginal rings, and injections. Less effective methods include physical barriers such as condoms, diaphragms and birth control sponges and fertility awareness methods. The least effective methods are spermicides and withdrawal by the male before ejaculation. Sterilization, while highly effective, is not usually reversible; all other methods are reversible, most immediately upon stopping them. Safe sex practices, such as with the use of male or female condoms, can also help prevent sexually transmitted infections. Other methods of birth control do not protect against sexually transmitted diseases. Emergency birth control can prevent pregnancy if taken within the 72 to 120 hours after unprotected sex. Some argue not having sex as a form of birth control, but abstinence-only sex education may increase teenage pregnancies if offered without birth control education, due to non-compliance.In teenagers, pregnancies are at greater risk of poor outcomes. Comprehensive sex education and access to birth control decreases the rate of unwanted pregnancies in this age group. While all forms of birth control can generally be used by young people, long-acting reversible birth control such as implants, IUDs, or vaginal rings are more successful in reducing rates of teenage pregnancy. After the delivery of a child, a woman who is not exclusively breastfeeding may become pregnant again after as few as four to six weeks. Some methods of birth control can be started immediately following the birth, while others require a delay of up to six months. In women who are breastfeeding, progestin-only methods are preferred over combined oral birth control pills. In women who have reached menopause, it is recommended that birth control be continued for one year after the last period.About 222 million women who want to avoid pregnancy in developing countries are not using a modern birth control method. Birth control use in developing countries has decreased the number of deaths during or around the time of pregnancy by 40% (about 270,000 deaths prevented in 2008) and could prevent 70% if the full demand for birth control were met. By lengthening the time between pregnancies, birth control can improve adult women's delivery outcomes and the survival of their children. In the developing world women's earnings, assets, weight, and their children's schooling and health all improve with greater access to birth control. Birth control increases economic growth because of fewer dependent children, more women participating in the workforce, and less use of scarce resources.

Birth rate

The birth rate (technically, births/population rate) is the total number of live births per 1,000 in a population in a year or period. The rate of births in a population is calculated in several ways: live births from a universal registration system for births, deaths, and marriages; population counts from a census, and estimation through specialized demographic techniques. The birth rate (along with mortality and migration rate) are used to calculate population growth.

The crude birth rate is the number of live births per year per 1,000 mid-year population. Another term used interchangeably with birth rate is natality. When the crude death rate is subtracted from the crude birth rate, the result is the rate of natural increase (RNI). This is equal to the rate of population change (excluding migration).The total (crude) birth rate (which includes all births)—typically indicated as births per 1,000 population—is distinguished from an age-specific rate (the number of births per 1,000 persons in an age group). The first known use of the term "birth rate" in English occurred in 1859.

The average global birth rate is 18.5 births per 1,000 total population in 2016.

The death rate is 7.8 per 1,000 per year. The RNI is thus 1.06 percent.

In 2012 the average global birth rate was 19.611 according to the World Bank and 19.15 births per 1,000 total population according to the CIA, compared to 20.09 per 1,000 total population in 2007.The 2016 average of 18.6 births per 1,000 total population is estimated to be about 4.3 births/second or about 256 births/minute for the world.

Demographic transition

The existence of some kind of demographic transition is widely accepted in the social sciences because of the well-established historical correlation linking dropping fertility to social and economic development. Scholars debate whether industrialization and higher incomes lead to lower population, or whether lower populations lead to industrialization and higher incomes. Scholars also debate to what extent various proposed and sometimes inter-related factors such as higher per capita income, higher female income, lower mortality, old-age security, and rise of demand for human capital are involved.

Demographics of India

India is the second most populated country in the world with nearly a fifth of the world's population. According to the 2017 revision of the World Population Prospects, the population stood at 1,324,171,354.

During 1975–2010 the population doubled to 1.2 billion. The Indian population reached the billion mark in 1998. India is projected to be the world's most populous country by 2024, surpassing the population of China. It is expected to become the first political entity in history to be home to more than 1.5 billion people by 2030, and its population is set to reach 1.7 billion by 2050. Its population growth rate is 1.13%, ranking 112th in the world in 2017.India has more than 50% of its population below the age of 25 and more than 65% below the age of 35. It is expected that, in 2020, the average age of an Indian will be 29 years, compared to 37 for China and 48 for Japan; and, by 2030, India's dependency ratio should be just over 0.4.India has more than two thousand ethnic groups, and every major religion is represented, as are four major families of languages (Indo-European, Dravidian, Austroasiatic and Sino-Tibetan languages) as well as two language isolates (the Nihali language spoken in parts of Maharashtra and the Burushaski language spoken in parts of Jammu and Kashmir (Kashmir).

Further complexity is lent by the great variation that occurs across this population on social parameters such as income and education. Only the continent of Africa exceeds the linguistic, genetic and cultural diversity of the nation of India.The sex ratio is 944 females for 1000 males (2016) (940 per 1000 in 2011) This ratio has been showing an upwards trend for the last two decades after a continuous decline in the last century.

Demography

Demography (from prefix demo- from Ancient Greek δῆμος dēmos meaning "the people", and -graphy from γράφω graphō, implies "writing, description or measurement") is the statistical study of populations, especially human beings. As a very general science, it can analyze any kind of dynamic living population, i.e., one that changes over time or space (see population dynamics). Demography encompasses the study of the size, structure, and distribution of these populations, and spatial or temporal changes in them in response to birth, migration, aging, and death. Based on the demographic research of the earth, earth's population up to the year 2050 and 2100 can be estimated by demographers. Demographics are quantifiable characteristics of a given population.

Demographic analysis can cover whole societies or groups defined by criteria such as education, nationality, religion, and ethnicity. Educational institutions usually treat demography as a field of sociology, though there are a number of independent demography departments.Formal demography limits its object of study to the measurement of population processes, while the broader field of social demography or population studies also analyses the relationships between economic, social, cultural, and biological processes influencing a population.

Demography of Australia

The demography of Australia covers basic statistics, most populous cities, ethnicity and religion. The population of Australia is estimated to be 25,369,400 as of 23 May 2019. Australia is the 52nd most populous country in the world and the most populous Oceanian country. Its population is concentrated mainly in urban areas and is expected to exceed 28 million by 2030.Australia's population has grown from an estimated population of between 300,000 and 1,000,000 at the time of British settlement in 1788 due to numerous waves of immigration during the period since. Also due to immigration from other continents, the European component's share of the population is declining as a percentage.Australia has an average population density of 3.3 persons per square kilometre of total land area, which makes it is one of the most sparsely populated countries in the world. This is generally attributed to the semi-arid and desert geography of much of the interior of the country. Another factor is urbanisation, with 89% of its population living in a handful of urban areas, Australia is one of the world's most urbanised countries. The life expectancy of Australia in 2015–2017 was 83.2 years, among the highest in the world.Australia generally doesn't collect data on race and ethnicity, with the exception of Australian Aboriginals and Torres Strait Islanders.

Family planning in India

Family planning in India is based on efforts largely sponsored by the Indian government. From 1965–2009, contraceptive usage has more than tripled (from 13% of married women in 1970 to 48% in 2009) and the fertility rate has more than halved (from 5.7 in 1966 to 2.4 in 2012), but the national fertility rate remains high, causing concern for long-term population growth. India adds up to 1,000,000 people to its population every 20 days. Extensive family planning has become a priority in an effort to curb the projected population of two billion by the end of the twenty-first century.

In 2015, the total fertility rate of India was 2.40 births per women and 15.6 million abortions performed, with an abortion rate of 47.0 abortions per 1000 women aged between 15–49 years. With high abortions rates follows a high number of unintended pregnancies, with a rate of 70.1 unintended pregnancies per 1000 women aged 15–49 years. Overall, the abortions occurring in India make up for one third of pregnancies and out of all pregnancies occurring, almost half were not planned. On the Demographic Transition Model, India falls in the third stage due to decreased birth rates and death rates. In 2026, it is projected to be in stage four once the Total Fertility Rate reaches 2.1.

Fertility awareness

Fertility awareness (FA) refers to a set of practices used to determine the fertile and infertile phases of a woman's menstrual cycle. Fertility awareness methods may be used to avoid pregnancy, to achieve pregnancy, or as a way to monitor gynecological health.

Methods of identifying infertile days have been known since antiquity, but scientific knowledge gained during the past century has increased the number and variety of methods.

Systems of fertility awareness rely on observation of changes in one or more of the primary fertility signs (basal body temperature, cervical mucus, and cervical position), tracking menstrual cycle length and identifying the fertile window based on this information, or both. Other signs may also be observed: these include breast tenderness and mittelschmerz (ovulation pains), urine analysis strips known as ovulation predictor kits (OPKs), and microscopic examination of saliva or cervical fluid. Also available are computerized fertility monitors.

Fertility medication

Fertility medication, better known as fertility drugs, are drugs which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary. There are currently very few fertility medication options available for men.Agents that enhance ovarian activity can be classified as either Gonadotropin releasing hormone, Estrogen antagonists or Gonadotropins.

In vitro fertilisation

In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm outside the body, in vitro ("in glass"). The process involves monitoring and stimulating a woman's ovulatory process, removing an ovum or ova (egg or eggs) from the woman's ovaries and letting sperm fertilise them in a liquid in a laboratory. After the fertilised egg (zygote) undergoes embryo culture for 2–6 days, it is implanted in the same or another woman's uterus, with the intention of establishing a successful pregnancy.

IVF is a type of assisted reproductive technology used for infertility treatment and gestational surrogacy. A fertilised egg may be implanted into a surrogate's uterus, and the resulting child is genetically unrelated to the surrogate. Some countries banned or otherwise regulate the availability of IVF treatment, giving rise to fertility tourism. Restrictions on the availability of IVF include costs and age, in order for a woman to carry a healthy pregnancy to term. IVF is generally not used until less invasive or expensive options have failed or been determined unlikely to work.

In 1978 Louise Brown was the first child successfully born after her mother received IVF treatment. Brown was born as a result of natural-cycle IVF, where no stimulation was made. The procedure took place at Dr Kershaw's Cottage Hospital (now Dr Kershaw's Hospice) in Royton, Oldham, England. Robert G. Edwards was awarded the Nobel Prize in Physiology or Medicine in 2010. The physiologist co-developed the treatment together with Patrick Steptoe and embryologist Jean Purdy but the latter two were not eligible for consideration as they had died and the Nobel Prize is not awarded posthumously.

With egg donation and IVF, women who are past their reproductive years, have infertile male partners, have idiopathic female-fertility issues, or have reached menopause, can still become pregnant. Adriana Iliescu held the record as the oldest woman to give birth using IVF and donated egg, when she gave birth in 2004 at the age of 66, a record passed in 2006. After the IVF treatment, some couples get pregnant without any fertility treatments. In 2018 it was estimated that eight million children had been born worldwide using IVF and other assisted reproduction techniques.

Infertility

Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects).

In humans, infertility is the inability to become pregnant after one year of intercourse without contraception involving a male and female partner. There are many causes of infertility, including some that medical intervention can treat. Estimates from 1997 suggest that worldwide about five percent of all heterosexual couples have an unresolved problem with infertility. Many more couples, however, experience involuntary childlessness for at least one year: estimates range from 12% to 28%. Male infertility is responsible for 20–30% of infertility cases, while 20–35% are due to female infertility, and 25–40% are due to combined problems in both parts. In 10–20% of cases, no cause is found. The most common cause of female infertility is ovulatory problems, which generally manifest themselves by sparse or absent menstrual periods. Male infertility is most commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity.Women who are fertile experience a natural period of fertility before and during ovulation, and they are naturally infertile for the rest of the menstrual cycle. Fertility awareness methods are used to discern when these changes occur by tracking changes in cervical mucus or basal body temperature.

List of fertility deities

A fertility deity is a god or goddess associated with fertility, pregnancy, and childbirth. In some cases these deities are directly associated with these experiences; in others they are more abstract symbols. Fertility rites may accompany their worship. The following is a list of fertility deities.

One-child policy

China's one-child policy was part of a birth planning program designed to control the size of its population. Distinct from the family planning policies of most other countries (which focus on providing contraceptive options to help women have the number of children they want), it set a limit on the number of children parents could have, the world's most extreme example of population planning. It was introduced in 1979 (after a decade-long two-child policy), modified in the mid 1980s to allow rural parents a second child if the first was a daughter, and then lasted three more decades before being eliminated at the end of 2015. The policy also allowed exceptions for some other groups, including ethnic minorities. The term one-child policy is thus a misnomer, because for nearly 30 of the 36 years that it existed (1979–2015) about half of all parents in China were allowed to have a second child.

Provincial governments could, and did, require the use of contraception, sterilizations and abortions to ensure compliance, and imposed enormous fines for violations. Local and national governments created commissions to raise awareness and carry out registration and inspection work. China also rewards families with only one child. From 1982 onwards, in accordance with the instructions on further family planning issued by the CPC central committee and the state council in that year, regulations awarded 5 yuan per month for only children. Parents who had one child would also get a “one-child glory certificate”.According to the Chinese government, 400 million births were prevented, starting from 1970, a decade before the start of the one child policy. Some scholars have disputed this claim, with Martin King Whyte and Wang et al contending that the policy had little effect on population growth or the size of the total population. China has been compared to countries with similar socioeconomic development like Thailand and Iran, along with the Indian states of Kerala and Tamil Nadu, which achieved similar declines of fertility without a one-child policy. However, a recent demographic study challenged these scholars by showing that China's low fertility was achieved two or three decades earlier than would be expected given its level of development, and that more than 500 million births were prevented between 1970 and 2015 (a calculation based on an alternative model of fertility decline proposed by the scholars themselves), some 400 million of which may have been due to one-child restrictions. In addition, by 2060 China's birth planning policies may have averted as many as 1 billion people in China when one adds in all the eliminated descendants of the births originally averted by the policies. Although 76% of Chinese people said that they supported the policy in a 2008 survey, it was controversial outside of China.Effective from January 2016, the national birth planning policy became a universal two-child policy that allowed each couple to have two children.

Reproductive endocrinology and infertility

Reproductive endocrinology and infertility (REI) is a surgical subspecialty of obstetrics and gynecology that trains physicians in reproductive medicine addressing hormonal functioning as it pertains to reproduction as well as the issue of infertility. While most REI specialists primarily focus on the treatment of infertility, reproductive endocrinologists are trained to also evaluate and treat hormonal dysfunctions in females and males outside infertility. Reproductive endocrinologists have specialty training in obstetrics and gynecology (ob-gyn) before they undergo sub-specialty training (fellowship) in REI.

Reproductive surgery is a related specialty, where a physician in ob-gyn or urology further specializes to operate on anatomical disorders that affect fertility.

Reproductive medicine

Reproductive medicine is a branch of medicine that deals with prevention, diagnosis and management of reproductive problems; goals include improving or maintaining reproductive health and allowing people to have children at a time of their choosing. It is founded on knowledge of reproductive anatomy, physiology, and endocrinology, and incorporates relevant aspects of molecular biology, biochemistry and pathology.

Soil fertility

Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality. A fertile soil has the following properties:

The ability to supply essential plant nutrients and water in adequate amounts and proportions for plant growth and reproduction; and

The absence of toxic substances which may inhibit plant growth.The following properties contribute to soil fertility in most situations:

Sufficient soil depth for adequate root growth and water retention;

Good internal drainage, allowing sufficient aeration for optimal root growth (although some plants, such as rice, tolerate waterlogging);

Topsoil with sufficient soil organic matter for healthy soil structure and soil moisture retention;

Soil pH in the range 5.5 to 7.0 (suitable for most plants but some prefer or tolerate more acid or alkaline conditions);

Adequate concentrations of essential plant nutrients in plant-available forms;

Presence of a range of microorganisms that support plant growth.In lands used for agriculture and other human activities, maintenance of soil fertility typically requires the use of soil conservation practices. This is because soil erosion and other forms of soil degradation generally result in a decline in quality with respect to one or more of the aspects indicated above.

Total fertility rate

The total fertility rate (TFR), sometimes also called the fertility rate, absolute/potential natality, period total fertility rate (PTFR), or total period fertility rate (TPFR) of a population is the average number of children that would be born to a woman over her lifetime if:

She was to experience the exact current age-specific fertility rates (ASFRs) through her lifetime, and

She was to survive from birth to the end of her reproductive life.It is obtained by summing the single-year age-specific rates at a given time.

United Nations Economic Commission for Europe

The United Nations Economic Commission for Europe (ECE) is one of the five regional commissions under the jurisdiction of the United Nations Economic and Social Council. It was established in order to promote economic cooperation and integrations among its Member States.

The Commission is composed of 56 Member States, most of which are based in Europe, as well as a few outside of Europe. Its transcontinental Eurasian and non-European Member States include: Armenia, Azerbaijan, Canada, Georgia, Israel, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, the United States of America and Uzbekistan.

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.