Fertility & FecundityFertility & Fecundity

Technology allows us to control reproduction….

This is more than just the pill and condomsCultural and Geographic variations & implications

Geographic Variation of Crude Birth Rate

Fertility vs Fecundity

Fecundity is a measure of the physical ability to have children

Fertility is the actual number of children a woman actually has

Infertility/Infecundity (for demographers)

Couples who have tried for 12 months to get pregnant and do not are infecund (AKA- infertile)

1995 this rate was 7% of American couples

1965 this rate was 11% of American couples

Fecundity and Age

For women, fecundity goes from 0 to non-zero at the onset of menarche (menstruation)

Female fecundity generally increases to their mid-20’s and drops to 0 at menopause

Male fecundity goes from 0 to non-zero at puberty and generally peaks in mid 20’s also

Male fecundity generally drops from mid 20’s as they age but does not have a definite end point like menopause.

Male fecundity tends to last longer than female fecundity

Some USA fecundity Statistics…

1998 10,000 babies born to women under 15.

1998 158 babies born to women of age 50-54

Ruth Kistler oldest natural US mother ever Gave birth to a child at age 57 in 1956

63 year old Phillipino woman in 1996 gave birth to an implanted embryo

What is ‘Maximum’ Fertility in absence of any fertility control?

1) Assume female fecundity from age 15-492) Assume 9 months of pregnancy3) Assume 18 months of breast feedingResult: 1 child every 2.2 yearsFertility Rate is 16 children per womanThis is a theoretical maximum for a population

(rarely happens)

No society produces this rate…

1) Pregnancy is dangerous. Many women would die before if not during the delivery of their 16th child

Not all women are fecund (1/3 of the women in Cameroon are infecund for health/dietary reasons)

If women don’t eat enough fat they may experience amenorhea (absence of suppression of menstruation and/or anovulatory cycles (egg-free menstruation))

Is Female Menarche (puberty) happening Earlier?

“The condition of accelerated puberty in girls is more of ahypothesis than a widely observed phenomenon—in spite of anecdotal reports. Your article seemed to emphasize the vaguepossibility that a host of chemicals, those found in the environmentor in foods, could initiate early puberty. But the only scientificallydocumented cause is the increase in childhood obesity, and thedemonstrated involvement of fat cell-derived leptin in initiatingpubertal events. Next time, I hope you will do your readers a favorby presenting such stories in a more realistic context, rather thanalarming them on the basis of weak scientific evidence.”

Ruth Kava, Ph.D., R.D. is Director of Nutrition of the American Council on Science and Health in New York.

‘Natural’ Fertility?

Definition: The level of reproduction that exists in the absence of deliberate (or at least modern) fertility control

‘Natural’ Fertility is much lower than ‘Maximum’ fertility

The Social Components of Fertility

Hunter-Gatherers: Space children in time, fertility much lower than ‘natural’ fertility

Agricultural Societies: High fertility perhaps from demand for people to harvest crops

Industrial Society: Very low fertility perhaps from the ‘expenses’ associated with raising kids

The Hutterites:A famous ‘High Fertility’ Society

Anabaptists (opposed to childhood baptism)Live in Agrarian communities in NE plains of

U.S. and Western provinces of Canada400 came from Russia in late 1800’sDoubled Population 6 times in 100 yearsIn 1936 the TFR for Hutterite women was 11

Why Hutterite Fertility so High?

Early age of marriageA good dietGood medical careBelief in Bible’s:“Be Fruitful and Multiply”

Frequent sex with no contraceptionHigh fertility is not rocket science

Hutterite Lifestyle (7:06) https://www.youtube.com/watch?v=QXvIPtAOeXU

Other ‘High Fertility’ Societies

Shipibo Indians from Eastern Amazon of Peru

-Avg Age at Marriage 14 -Avg Age at 1st Child 15.6 - Total Fertility Rate ~ 11

Hmong Refugees to U.S. in 1980’s

same deal: Marry Early, impregnate often

Total Fertility Rate ~ 11

Age Specific Fertility

Rate