Fertility
Encyclopedia
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity
, which is defined as the potential for reproduction (influenced by gamete production, fertilisation and carrying a pregnancy to term). A lack of fecundity would be called sterility
.
Human fertility depends on factors of nutrition
, sexual behavior, culture
, instinct
, endocrinology
, timing, economics
, way of life, and emotion
s.
. 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.
TFR = TF × Cm × Ci × Ca × Cc
These four indices can also be use to calculate the Total Marital Fertility (TMFR) and the Total Natural Fertility (TN.
TFR = TMFR × Cm
TMFR = TN × Cc × Ca
TN = TF × Ci
Intercourse
Conception
Gestation
and when a man is most virile. The female cycle is approximately twenty-eight days long, but the male cycle is variable. Men can ejaculate and produce sperm
at any time of the month, but their sperm quality dips occasionally, which scientists guess is in relation to their internal cycle.
Furthermore, age also plays an equally significant role for both men and women.
, peak fertility occurs during just a few days of the cycle: usually two days before and two days after the ovulation date. This fertile window varies from woman to woman, just as the ovulation date often varies from cycle to cycle for the same woman. 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 to 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.
in the United States is about 12.5 years.
In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year.
Women's fertility peaks between the ages of 22 to 26. However, 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. Results of the study are published in the journal Science. With a rise in women postponing pregnancy
, this can create an infertility
problem.
According to the March of Dimes
, "about 9 percent of recognised 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".
In 2010, researchers at the University of Edinburgh
determined that by the time women are 30 years old, only 10% of their non-growing follicles
(NGFs) remain. At birth, women have all their follicles for folliculogenesis
, and they steadily decline until menopause
.
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, a woman has about a 1-in-1,250 chance of having a baby with Down syndrome
; at age 30, a 1-in-1,000 chance; at age 35, a 1-in-400 chance; at age 40, a 1-in-100 chance; and at 45, a 1-in-30 chance."
According to Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research,
of women trying to get pregnant, without using fertility drugs or in vitro fertilization:
The use of fertility drugs
and/or invitro fertilization can increase the chances of becoming pregnant at a later age. Successful pregnancies facilitated by fertility treatment have been documented in women as old as 67.
, and sperm morphology. In studies that controlled for female age, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rate
s between 23% and 38%.
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. However, an even larger difference is seen in how many of the seminiferous tubules
in the testes contain mature sperm;
Research shows increased risks for health problems for children of older fathers. A large scale Israel
i study found 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. Increased paternal age
has also been correlated to schizophrenia in numerous studies.
Australian researchers have found evidence to suggest overweight obesity may cause subtle damage to sperm and prevent health pregnancy. They say fertilization was 40% less likely to succeed when the father was overweight.
The American Fertility Society recommends an age limit for sperm donors of 50 years or less, and many fertility clinic
s in the United Kingdom
will not accept donations from men over 40 or 45 years of age. In part because of this fact, more women are now using a take-home baby rate calculator to estimate their chances of success following invitro fertilization.
pronatalist movement from 1919-1945 failed to convince French couples of having 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.
developed a theory (the Easterlin hypothesis
) to account for the Baby Boom. He assumes first that young couples try to achieve a standard of living
equal to or better than they had when they grew up. This is called "relative status"; in other words, young men in one cohort compare themselves now to where their own fathers in a previous cohort had been. Second, Easterlin assumes that when jobs are plentiful, it will be easier to marry young and have more children and still match that standard of living. But when jobs are scarce, couples who try to keep that standard of living will wait to get married and have fewer children. For Easterlin, the size of the cohort is a critical determinant of how easy it is to get a good job. A small cohort means less competition, a large cohort means more competition to worry about. The assumptions blend economics
and sociology
, and Easterlin did not rely on surveys or interviews asking people what really motivated them.
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
, which is defined as the potential for reproduction (influenced by gamete production, fertilisation and carrying a pregnancy to term). A lack of fecundity would be called sterility
Sterility (physiology)
Sterility is the physiological inability to effect sexual reproduction in a living thing, members of whose kind have been produced sexually. The term may be used in reference to* types of organism, such as the mule, a sterile hybrid;...
.
Human fertility depends on factors of nutrition
Nutrition
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
, sexual behavior, culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...
, instinct
Instinct
Instinct or innate behavior is the inherent inclination of a living organism toward a particular behavior.The simplest example of an instinctive behavior is a fixed action pattern, in which a very short to medium length sequence of actions, without variation, are carried out in response to a...
, endocrinology
Endocrinology
Endocrinology is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions called hormones, the integration of developmental events such as proliferation, growth, and differentiation and the coordination of...
, timing, economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...
, way of life, and emotion
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
s.
Demography
In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to produce which is termed fecundityFecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
. 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
Cohort (statistics)
In statistics and demography, a cohort is a group of subjects who have shared a particular time together during a particular time span . Cohorts may be tracked over extended periods in a cohort study. The cohort can be modified by censoring, i.e...
" 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.
Period measures
- Crude birth rate (CBR) - the number of live birthLive birthIn human reproduction, a live birth occurs when a fetus, whatever its gestational age, exits the maternal body and subsequently shows any sign of life, such as voluntary movement, heartbeat, or pulsation of the umbilical cord, for however brief a time and regardless of whether the umbilical cord or...
s 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
- Age-specific fertility rate (ASFR) - The number of births in a year to women in a 5-year age group, divided by the number of all women in that age group, times 1000. The usual age groups are 10-14, 15-19, 20-24, etc.
- Total fertility rateTotal Fertility RateThe total fertility rate of a population is the average number of children that would be born to a woman over her lifetime if she were to experience the exact current age-specific fertility rates through her lifetime, and she...
(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. - 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 59; 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 determinants of fertility
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: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 use 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 intercourseSexual intercourseSexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...
, and an examination of the average age at first intercourse, the average frequency outside marriage, and the average frequency inside.
Conception
Conception
Conception, or a concept, is an abstract idea or a mental symbol.Conception may also refer to:* Conception, or fertilisation, the fusion of gametes to produce a new organism.* Conception , an album by Miles Davis...
- 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 gonorrheaGonorrheaGonorrhea is a common sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. The usual symptoms in men are burning with urination and penile discharge. Women, on the other hand, are asymptomatic half the time or have vaginal discharge and pelvic pain...
, syphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
, and chlamydia) are common causes. NutritionNutritionNutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
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 anorexiaAnorexia nervosaAnorexia nervosa is an eating disorder characterized by refusal to maintain a healthy body weight and an obsessive fear of gaining weight. Although commonly called "anorexia", that term on its own denotes any symptomatic loss of appetite and is not strictly accurate...
. 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 breastfeedingBreastfeedingBreastfeeding is the feeding of an infant or young child with breast milk directly from female human breasts rather than from a baby bottle or other container. Babies have a sucking reflex that enables them to suck and swallow milk. It is recommended that mothers breastfeed for six months or...
. 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 contraceptiveContraceptionContraception is the prevention of the fusion of gametes during or after sexual activity. The term contraception is a contraction of contra, which means against, and the word conception, meaning fertilization...
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 ligationTubal ligationTubal ligation or tubectomy is a surgical procedure for sterilization in which a woman's fallopian tubes are clamped and blocked, or severed and sealed, either method of which prevents eggs from reaching the uterus for fertilization...
(sterilizationSterilization (surgical procedure)Sterilization refers to any of a number of medical techniques that intentionally leave a person unable to reproduce. It is a method of birth control. For other causes of sterility, see infertility....
) of the woman, or a vasectomyVasectomyVasectomy is a surgical procedure for male sterilization and/or permanent birth control. During the procedure, the vasa deferentia of a man are severed, and then tied/sealed in a manner such to prevent sperm from entering into the seminal stream...
for the man.
Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
- After a fetusFetusA fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
is conceived, it may or may not survive to birth. "Involunatry fetal mortality" involves natural abortionmiscarriageMiscarriageMiscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
s and stillbirthStillbirthA stillbirth occurs when a fetus has died in the uterus. The Australian definition specifies that fetal death is termed a stillbirth after 20 weeks gestation or the fetus weighs more than . Once the fetus has died the mother still has contractions and remains undelivered. The term is often used in...
(a fetus born dead). Human intervention intentionally causing abortion of the fetus is called "therapeutic abortionTherapeutic abortionTherapeutic abortion is abortion induced following a medical diagnosis. Many therapeutic abortions are performed today, with some degree of controversy regarding the quality of life, if there is a genetic condition in the embryo or fetus which is incompatible with life Therapeutic abortion is...
".
Human fertility
Both women and men have hormonal cycles which determine both when a woman can achieve pregnancyPregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
and when a man is most virile. The female cycle is approximately twenty-eight days long, but the male cycle is variable. Men can ejaculate and produce sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
at any time of the month, but their sperm quality dips occasionally, which scientists guess is in relation to their internal cycle.
Furthermore, age also plays an equally significant role for both men and women.
Menstrual cycle
Although women can become pregnant at any time during their menstrual cycleMenstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
, peak fertility occurs during just a few days of the cycle: usually two days before and two days after the ovulation date. This fertile window varies from woman to woman, just as the ovulation date often varies from cycle to cycle for the same woman. The ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...
is usually capable of being fertilized for up to 48 hours after it is released from the ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
. Sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
survive inside the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
between 48 to 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
Rhythm Method
Calendar-based methods are various methods of estimating a woman's likelihood of fertility, based on a record of the length of previous menstrual cycles. Various systems are known as the Knaus–Ogino Method, rhythm method, and Standard Days Method...
of contraception.
Female fertility
The average age of menarcheMenarche
Menarche is the first menstrual cycle, or first menstrual bleeding, in female human beings. From both social and medical perspectives it is often considered the central event of female puberty, as it signals the possibility of fertility....
in the United States is about 12.5 years.
In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year.
Women's fertility peaks between the ages of 22 to 26. However, 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. Results of the study are published in the journal Science. With a rise in women postponing pregnancy
Advanced maternal age
Advanced maternal age is defined as an increase in the age at which women give birth to their first child, is now a widespread, and indeed near universal, phenomenon across the OECD countries....
, this can create an infertility
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...
problem.
According to the March of Dimes
March of Dimes
The March of Dimes Foundation is a United States nonprofit organization that works to improve the health of mothers and babies.-Organization:...
, "about 9 percent of recognised 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".
In 2010, researchers at the University of Edinburgh
University of Edinburgh
The University of Edinburgh, founded in 1583, is a public research university located in Edinburgh, the capital of Scotland, and a UNESCO World Heritage Site. The university is deeply embedded in the fabric of the city, with many of the buildings in the historic Old Town belonging to the university...
determined that by the time women are 30 years old, only 10% of their non-growing follicles
Folliculogenesis
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely-packed shell of somatic cells that contains an immature oocyte...
(NGFs) remain. At birth, women have all their follicles for folliculogenesis
Folliculogenesis
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely-packed shell of somatic cells that contains an immature oocyte...
, and they steadily decline until menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...
.
Birth defects, especially those involving chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
number and arrangement, also increase with the age of the mother. According to the March of Dimes, "At age 25, a woman has about a 1-in-1,250 chance of having a baby with Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
; at age 30, a 1-in-1,000 chance; at age 35, a 1-in-400 chance; at age 40, a 1-in-100 chance; and at 45, a 1-in-30 chance."
According to Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research,
of women trying to get pregnant, without using fertility drugs or in vitro fertilization:
- 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.
The use of fertility drugs
Fertility medication
Fertility medication are drugs which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary...
and/or invitro fertilization can increase the chances of becoming pregnant at a later age. Successful pregnancies facilitated by fertility treatment have been documented in women as old as 67.
Male fertility
Evidence shows that increased male age is associated with a decline in semen volume, sperm motilitySperm motility
Sperm motility describes the ability of sperm to move properly towards an egg. This can also be thought of as the 'quality' of the sperm, which is a factor in successful pregnancies, as opposed to the 'quantity'. Sperm which do not properly 'swim', will not reach the egg in order to fertilize it...
, and sperm morphology. In studies that controlled for female age, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rate
Pregnancy rate
Pregnancy rate in infertility treatment is the success rate for pregnancy. It is the percentage of all attempts that leads to pregnancy, with attempts generally referring to menstrual cycles where insemination or any artificial equivalent is used, which may be simple artificial insemination or AI...
s between 23% and 38%.
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. However, an even larger difference is seen in how many of the seminiferous tubules
Seminiferous tubules
Seminiferous tubules are located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa....
in the testes contain mature sperm;
- 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.
Research shows increased risks for health problems for children of older fathers. A large scale Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
i study found 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
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, controlling for year of birth, socioeconomic status, and maternal age. Increased paternal age
Paternal age effect
The paternal age effect can refer to the statistical relationships of: a man's age to sperm and semen abnormalities; a man's age to his fertility; a man's age to adverse pregnancy outcomes in his female partner ; a father's age at the birth of his offspring on the probability of an adverse...
has also been correlated to schizophrenia in numerous studies.
Australian researchers have found evidence to suggest overweight obesity may cause subtle damage to sperm and prevent health pregnancy. They say fertilization was 40% less likely to succeed when the father was overweight.
The American Fertility Society recommends an age limit for sperm donors of 50 years or less, and many fertility clinic
Fertility clinic
Fertility clinics are staffed medical clinics that assist couples, and sometimes individuals, who want to become parents but for medical reasons have been unable to achieve this goal via the natural course...
s in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
will not accept donations from men over 40 or 45 years of age. In part because of this fact, more women are now using a take-home baby rate calculator to estimate their chances of success following invitro fertilization.
France
The FrenchFrance
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
pronatalist movement from 1919-1945 failed to convince French couples of having a patriotic
Patriotism
Patriotism is a devotion to one's country, excluding differences caused by the dependencies of the term's meaning upon context, geography and philosophy...
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.
Post-WW II USA
From 1800 to 1940, fertility fell steadily in the US. Then suddenly it 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. After 1960, ideal family size fell sharply, from 3 to 2 children. Couples postponed marriage and first births, and they sharply reduced the number of third and fourth births.Easterlin Model
American Economist Richard EasterlinRichard Easterlin
Richard A. Easterlin is University Professor and Professor of Economics at the University of Southern California. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences...
developed a theory (the Easterlin hypothesis
Easterlin hypothesis
The Easterlin hypothesis states that the positive relationship between income and fertility is dependent on relative income. The hypothesis as formulated by Richard Easterlin presumes that material aspirations are determined by experiences rooted in family background. If income is high relative to...
) to account for the Baby Boom. He assumes first that young couples try to achieve a standard of living
Standard of living
Standard of living is generally measured by standards such as real income per person and poverty rate. Other measures such as access and quality of health care, income growth inequality and educational standards are also used. Examples are access to certain goods , or measures of health such as...
equal to or better than they had when they grew up. This is called "relative status"; in other words, young men in one cohort compare themselves now to where their own fathers in a previous cohort had been. Second, Easterlin assumes that when jobs are plentiful, it will be easier to marry young and have more children and still match that standard of living. But when jobs are scarce, couples who try to keep that standard of living will wait to get married and have fewer children. For Easterlin, the size of the cohort is a critical determinant of how easy it is to get a good job. A small cohort means less competition, a large cohort means more competition to worry about. The assumptions blend economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...
and sociology
Sociology
Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...
, and Easterlin did not rely on surveys or interviews asking people what really motivated them.
See also
- Birth controlBirth controlBirth control is an umbrella term for several techniques and methods used to prevent fertilization or to interrupt pregnancy at various stages. Birth control techniques and methods include contraception , contragestion and abortion...
- Demographic-economic paradoxDemographic-economic paradoxThe demographic-economic paradox is the inverse correlation found between wealth and fertility within and between nations. The higher the degree of education and GDP per capita of a human population, subpopulation or social stratum, the fewer children are born in any industrialized country...
- Family economicsFamily economicsThe family, although recognized as fundamental from Adam Smith on, received little systematic treatment in economics before the 1950s. A significant exception was Thomas Malthus's model of population growth. The work of Gary Becker and others initiated contemporary research on family economics ...
- Family planningFamily planningFamily planning is the planning of when to have children, and the use of birth control and other techniques to implement such plans. Other techniques commonly used include sexuality education, prevention and management of sexually transmitted infections, pre-conception counseling and...
- Fertility clinicFertility clinicFertility clinics are staffed medical clinics that assist couples, and sometimes individuals, who want to become parents but for medical reasons have been unable to achieve this goal via the natural course...
- Fertility tourismFertility tourismFertility tourism or reproductive tourism is the practice of traveling to another country for fertility treatments. It may be regarded as a form of medical tourism. The main reasons for fertility tourism are legal regulation of the sought procedure in the home country, or lower price...
- Fertility deity
- Fertility preservationFertility preservationFertility preservation is the effort to help cancer patients retain their fertility, or ability to procreate. Research into how cancer affects reproductive health and preservation options are growing, sparked in part by the increase in the survival rate of cancer patients.-Indications:Fertility...
- Fertility and intelligenceFertility and intelligenceFertility and intelligence research investigates the relationship between fertility and intelligence. Demographic studies have indicated that in humans, fertility and intelligence tend to be inversely correlated, that is to say, the more intelligent, as measured by IQ tests, exhibit a lower total...
- Human Fertilisation and Embryology AuthorityHuman Fertilisation and Embryology AuthorityThe Human Fertilisation and Embryology Authority is a statutory body in the United Kingdom that regulates and inspects all UK clinics providing in vitro fertilisation, artificial insemination and the storage of human eggs, sperm or embryos. It also regulates Human Embryo research...
- Natural fertilityNatural fertilityNatural fertility method of birth control is a concept developed by French historical demographer Louis Henry to refer to the level of fertility that would prevail in a population that makes no conscious effort to limit, regulate, or control fertility, so that fertility depends only on...
- OncofertilityOncofertilityThe Oncofertility Consortium is a multi-institutional project to assess the impact of cancer and its treatment on reproductive health. The term oncofertility refers to a new interdisciplinary field that bridges oncology and women’s health research for the purpose of exploring and expanding options...
- Reproductive healthReproductive healthWithin the framework of the World Health Organization's definition of health as a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity, reproductive health, or sexual health/hygiene, addresses the reproductive processes, functions and system...
- Total fertility rateTotal Fertility RateThe total fertility rate of a population is the average number of children that would be born to a woman over her lifetime if she were to experience the exact current age-specific fertility rates through her lifetime, and she...
- Fertility-development controversyFertility-development controversyThe relationship between the total fertility rate and socio-economic development, which is measured by the human development index , is the subject of debate in social sciences....
Further reading
- Fertility treatment and clinics in the UK - HFEA
- Jorge Chavarro (2009) The Fertility Diet: Groundbreaking Research Reveals Natural Ways to Boost Ovulation and Improve Your Chances of Getting Pregnant, McGraw-Hill Professional. ISBN 978-0-07-162710-8
External links
- United Nations World Population Prospects, the 2008 Revision, Data on fertility trends worldwide