Fertility

Source: Wikipedia, the free encyclopedia.
(Redirected from
Male fertility
)
This article is about fertility in humans. For fertility of other organisms, see fecundity. For fertility of plants and soil, see Soil fertility.

Fertility is the ability to

fertility specialists
all over the world assist persons and couples who experience difficulties conceiving a baby.

Fertility is an issue for people of both sexes. According to the Centers for Disease Control and Prevention, in 35% of couples who cannot conceive, the cause can be attributed to factors on both the female and male side.[1] Human fertility depends on various factors including nutrition, sexual behaviour, consanguinity, culture, instinct, endocrinology, timing of conception, economics, personality,[2] lifestyle, and emotions.

Fertility differs from fecundity, which is defined as the biological capacity to reproduce irrespective of intention for conception.[3] Fecundity can be explained by gamete production, fertilization, and carrying a pregnancy to term.[4] The antithesis of fertility is infertility, while the antithesis of fecundity is sterility.

Demography

In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to produce which is termed fecundity.[5][6] 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.[7]

Period measures

Cohort measures

Countries by fertility rate as of 2020
  • 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.[8]
  • 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

Main article: fertility factor (demography)

A parent's number of children strongly correlates with the number of children that each person in the next generation will eventually have.

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:

New Home Economics. Influential economic analyses of fertility include Becker (1960),[21] Mincer (1963),[22] and Easterlin (1969).[23] 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."
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
therapeutic abortion
".

Fertility biology

Women have

sperm quality is affected by their health, frequency of ejaculation, and environmental factors.[24]

Fertility declines with age in both sexes. For women, the decline begins around the age of 32, and becomes precipitous at age 37. For men, potency and sperm quality begins to decline around the age of 40. Even if an older couple does manage to conceive a child, the pregnancy will be increasingly difficult for the mother, and carries a higher risk of birth defects and genetic disorders for the child.[25]

sex positions and pregnancy rate, as long as it results in ejaculation into the vagina.[28]

Menstrual cycle

Main article: Menstrual cycle
Chance of fertilization by menstrual cycle day relative to ovulation[29]

A woman's menstrual cycle begins, as 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 completes maturation and enables the ovum to break through the ovary wall.[30] This is ovulation. During the luteal phase following 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.

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

Further information: Female infertility

The average age of menarche in the United States is about 12.5 years.[33] 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.[34]

Menopause occurs during a woman's midlife between ages 48 and 55.[35][36] During menopause, hormonal production by the ovaries is reduced, eventually causing a permanent cessation of the creation of the uterine lining (period). This is considered the end of the fertile phase of a woman's life.

The predicted effect of age on female fertility in women trying to get pregnant, without using fertility drugs or in vitro fertilization:[37]

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

[37]

Studies of couples trying to conceive have yielded better results: one 2004 study of 770 European women found that 82% of 35- to 39-year-old women conceived within a year,[38] while a study in 2013 of 2,820 Danish women saw 78% of 35- to 40-year-olds conceive within a year.[39]

According to an opinion by the Practice Committee of the American Society for Reproductive Medicine, specific coital timing or position, and resting supine after intercourse have no significant impact on fertility. Sperm can be found in the cervical canal seconds after ejaculation, regardless of coital position.[40]

Successful pregnancies facilitated by fertility treatment have been documented in women as old as 67.[41]

Male fertility

See also: Paternal age effect and Male infertility

Some research suggests that older males have decreased semen volume,

testes containing mature sperm:[42]

Decline in male fertility is influenced by many factors, including lifestyle, environment and psychological factors.[44]

Some research suggests increased risks for health problems for children of older fathers, but no clear association has been proven.

autism spectrum disorder, controlling for year of birth, socioeconomic status, and maternal age.[46] Increased paternal age has been suggested to correlate with schizophrenia but it is unproven.[47][48][49][50][51]

Australian researchers have found evidence to suggest obesity may cause subtle damage to sperm and prevent a healthy pregnancy. They reported fertilization was 40% less successful when the father was overweight.[52]

The

American Fertility Society recommends an age limit for sperm donors of 50 years or less,[53] and many fertility clinics in the United Kingdom will not accept donations from men over 40 or 45 years of age.[54]

Historical trends by country

Main article: Historical demography
See also: Demographic transition

France

Main article: Demographics of France

The

fertility treatments for all women regardless of sexual orientation or marital status. Soon there will be no reason for lesbian couples or single women to travel to be able to start their own family.[56]

Korea

Main article:
Low birth rate in South Korea
Total fertility rate in Korea

South Korea has the lowest fertility rate in the world at 0.78.[57] A variety of explanations have been proposed, ranging from investment in education[58] to birth control, abortion, a decline in the marriage rate, divorce, female participation in the labor force, and the 1997 Asian financial crisis.[59] After being legal from the 1960s to the 1980s, abortion was again made illegal in South Korea in the early 2000s in an attempt to reverse the declining fertility rate.[60]

United States

Main article: Demographic history of the United States
United States crude birth rate (births per 1000 population); Baby Boom years in red.[61]

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.

Post-WWII

Main article:
Baby Boom

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.[62]

Sexual revolution

See also:
Sexual revolution in 1960s America

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.[63]

Impact of external factors on fertility

Studies have been conducted to identify external factors that impact fertility rates and embryo development. Two main factors were determined to have the greatest impact, eating habits and lifestyle choices.[64] Eating choices include quality, types and frequency of food intake. Grains, fruits and vegetables have a positive influence on embryo quality. Alcohol intake, cigarette and marijuana use all have a detrimental impact on female reproductive function.[65] During embryogenesis, the DNA structure and expression can be heavily influenced by lifestyle, nutrition and environmental toxins.[66]

Infertility

Main article: Infertility

full term. There are many biological causes of infertility, including some that medical intervention can treat.[67]

See also

Further reading

References

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  6. ^ Last JM. "Fecundity and Fertility". Encyclopedia of Public Health. Archived from the original on 11 August 2009 – via enotes.com.
  7. ^ For detailed discussions of each measure see Paul George Demeny and Geoffrey McNicoll, Encyclopedia of Population (2003)
  8. ^ 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).
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Further reading

This article incorporates material from the

Creative Commons Attribution-ShareAlike 3.0 Unported License but not under the GFDL
.

External links

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