soci final exam fertility and infertility

Fertility

-        number of children that are actually born to women

o   a behavioral outcome shaped by biological, social, economic, and cultural factors

Fecundity

• The physiological capacity to become pregnant and carry a pregnancy to term.

• Distinct from fertility: a woman can be highly fecund but have low fertility if she limits births.

female reproductive period

age 15-40

• menarche can start at age 10 or younger but usually at 12. age declined over time in more developed countries. it can occur as late as 18

• chance of conception is low directly after menarche

females stop being able to become pregnant at menopause .

• average age at menopause is about 50 in the more developed regions and it seems to have become older over time in the less developed regions

Crude Birth Rate (CBR)

( births/ mid year pop )×1000

General Fertility Rate (GFR)

(births/ mid-year women pop 15-49) x 1000

More precise than CBR because it includes only women able to give birth.

Why is the GFR difference from 1940 → 1960 larger than CBR difference?

• Because the proportion of women in childbearing ages increased, amplifying fertility even if the broader population changed less.

Age-Specific Fertility Rates (ASFR)

ASFR​= (nBx/ nWx)×1000

nBx= Birhts to W. x to x+n

nWx: Women Pop x to x+n

• Measures fertility at specific ages (e.g., 15–19, 20–24, etc.).

• Shows where fertility concentrates (peak ages differ across populations).

• ASFR decreased from 1960 to 2000 for all ages

Total Fertility Rate (TFR)

TFR=∑ASFR× (n/1000)

total number of children that a woman can expect to bare if she survives to the end of childbearing age and is exposed to the age specific fertility rates of a given period

Gross Reproduction Rate (GRR)

GRR = ΣASFRf * (n/1000)n/ 1000

GRR=TFR×0.49

Measures number of daughters born to a woman (assuming 49% of births are female).

general fertility rate went up from 1940 to 1960 and then declined 1960 to 2000

Net Reproduction Rate (NRR)

• measures number female children a women can expected given she survives to have children

• accounts for mortality

• NRR OF 1 IS EXACTLY replacement level: each woman is living long enough, and the fertility is the level, that they will have one female child

• if mortality is high, it make take a TFR of 2.5 or higher to get an NRR of 1.0. if mortality is low, as in MDCs today, a TFR of about 2.1 gives an NRR of 1.0

Net Reproduction Rate Shortcut

NRR=GRR×p(a)

where p(a) = probability of surviving to average age of childbearing (~30).

So even if fertility was higher in 1940, many more women died before or during childbearing ages, reducing the number of daughters that a woman actually lived long enough to have. Despite a higher GRR in 1940, the NRR is about the
same as in 2000.

Mean Age of Childbearing (MAC)

• weighted average age at which women give birth

• reflects timing of fertility (tempo)

cohort fertility measure : CEB

• determine cohort feritlity rate by average children ever born (CEB) to a cohort of women.

• only computable once women have passed childbearing years

• The great depression reduced births during that period, while the war increased it after it ended. if these periods had an effect on childbirth, without altering the total number of children born to women, it is said to have a period effect.

• cohort fertility is more stable than period fertility over time b/c fertility patterns don’t change as quickly as period rates would display.

  • we have to wait until a group has completed fertility to get cohort measures of fertility

period vs cohort

Period Measures

• Project fertility of a hypothetical woman using current-year rates.

• Highly sensitive to timing changes (tempo distortions).

• Example from slides: A spike year in births inflates TFR artificially.

• most of our measures are period measures, because this info is easy to get

• doesn’t tell us true fertility of a group, only a guess given current situation

Cohort Measures

• Actual children born to women of a specific birth cohort.

• More stable over time because real behavior changes slowly.

• Available only after cohort completes fertility.

birth interval

wait to conception —> pregnancy/ birth, miscarriage or abortion/ wait to conception —> time

end of pregnancy, period of time that woman cannot or is unlikely to get pregnant.

• this period of time is often extended by breastfeeding.

women not able to get pregnany: amenorrhea

each induced abortion or miscarriage averts less than one birth, in a birth interval sense

proximate determinants of fertility

example: high education —> greater use of conrtraception —> low fertility

directly influences fertility rates within a society

to change fertility levels, there must be changes in the proximate determinants

PD- intercourse variables

• Age at marriage/union formation

• Cohabitation patterns

• Divorce, widowhood

• Voluntary abstinence

• Involuntary abstinence (impotence, illness, work separation)

• Coital frequency

PD- Exposure to conception

• periods of fecundity or infecundity, such as affected by breastfeeding or as affected by sterilization or medical treatment

• use or no-use of contraception

PD- gestation and carrying the pregnancy to birth

• miscarriage (also called spontaneous abortion)

• induced abortion

Natural Fertility

Number of children one can expect in a society where there is no deliberate attempt to limit births

• no society ever has maximum fertility

• individual level control: ABSTINENCE

• social level control: marraige, social custom on breat feeding, living arrangement

• social components determine fertility to a much greater extent than biological in society

hutterites

religious group that came from eastern europe and settled in the northwest US and southwest Canada

believe that it is morally wrong for a married couple to do anything to prevent a pregnancy

group often noted for their high fertility. they traditionally have maintained an average of about 11 births per woman

shape of the hutterite age specific fertility schedule is thought to show the relative fecundity of women at various ages

Louis Henry’s definition of natural fertiltity

coined the term

Natural fertility exists when behaviors affecting conception and birth are not modified based on number of prior children.

does not mean having children at the biological maximum

parity is the numbering of a birth, after one child, a woman is at parity 1, after 2= parity 2. if she behaves the same way after the fourth birth as after the first birth, then her behavior is not parity dependent

when behavior that postpones the next pregnancy or birth is parity dependent, controlled fertility behavior is being practiced

postpartum abstienence in africa

• some parts of sub-saharan africa practice voluntary fertility limitation which is not parity dependent, and the intention is not to limit the total number of children

• high infant mortality in sub saharan africa

• if the birth interval is too short, this increases the chance that the firstborn child will die

• some abstain from sexual intercourse for an extendend period of time after a child’s birth to increase the chance the child will survive

factors influencing time women spend in sexual unions

womens age of marriage or age of entry into a sexual union

proportion of women never marrying or remaining celibate

amount of time women spend between sexual unions

factors influencing conception- exposure within a sexual union

 Average coital frequency
 Proportion voluntarily abstinent within the union
 Proportion involuntarily abstinent
 Probability and type of contraception used
 Infecundity by involuntary causes, mostly length of breast
feeding.
 Infecundity by voluntary causes, mostly sterilization

contraceptive prevalence and unmet needs for family planing

Women are classified as having unmet need if they:

1. Are fecund (able to become pregnant), Sexually active, Want to delay or stop childbearing, Are not using any form of contraception.

A woman is also counted as unmet need if:

• She is pregnant with an unwanted or mistimed pregnancy, OR

• She is postpartum amenorrheic, not using contraception, and her last birth was unwanted or mistimed.

Interpretation:

• High unmet need = major barrier to reproductive rights

• Indicates gaps in:

  • Access, Information, Social acceptance, and Availability of modern methods

factors influencing gestation

• Involuntary abortions or miscarriages

• Voluntary abortions

  • Single most widely used form of birth control in the world. In
    1995 there were 46 millions abortions worldwide

  • 1 in 4 pregnancies in the world / U.S ends in abortion

  • Abortion is popular both where it is legal and illegal

  • 44% of abortions worldwide are not legal

  • Abortion is used more often when

  • other methods of contraception are unavailable

  • abstinence is a politically favored method of birth control

  • there are weak structures in place promoting other method

  • Social acceptance of abortion does not necessarily reduce
    abortion prevalence.

most important proximate determinants

age at marriage (exposure to sexual union)

breast feeding (influencing involuntary infecundity)

prevalence of contraception use

prevalence of abortion

maximum number of births

Scenario 1 — Married at 15, no breastfeeding

• Fecund for 420 months

• 420 / 18 months between births = 23 births (max biological estimate)

Scenario 2 — Married at 25, no breastfeeding

• Fecund 300 months

• 300 / 18 months between births = 16.7 births

Scenario 3 — Married at 25, breastfeeds

• Breastfeeding adds 9 months infecundability (can’t have kids) → 27 months/birth

• 300 / 27 = 11 births

Scenario 4 — Contraceptive 98% effective

• Contraceptive adds 1 / .02 = 50 months

• Interval = 18 + 9 + 50 = 77 months

• 300 / 77 ≈ 3 births

Scenario 5 — Include 1 abortion

• Abortion adds 3 + 4 = 7 months

• Interval: 18 + 9 + 50 + 7 + 50 = 134 months

• 300 / 134 ≈ 2 births

These scenarios illustrate the proximate determinants framework: changes in exposure, contraception, breastfeeding, and gestation outcomes directly affect fertility.

Replacement Level Fertility

• Replacement level fertility depends on mortality rates.

• In low-mortality countries → TFR ≈ 2.1 → NRR = 1.

• In high-mortality countries → may require TFR ≥ 2.5.

• NRR is the strongest indicator of replacement because it incorporates female births and mortality.

Fertility, Infertility, and Voluntary vs. Involuntary Childlessness

Voluntary vs. Involuntary Fertility Outcomes

• Childlessness may be voluntary (“child-free”) or involuntary (infertility, lacking partner, medical barriers).

• Research (Hagewen & Morgan 2005; Quesnel-Vallée & Morgan 2003) shows:

  • Many adults express fertility intentions that do not align with eventual outcomes.

  • Life-course constraints (partnership timing, health, economic stability) play a large role in determining whether fertility intentions are realized.

Infertility

• Can be voluntary (choosing not to have children) or involuntary (biological or situational barriers).

• Biological infertility risk increases significantly with age due to declining fecundity.

Assisted Reproductive Technologies (ART)

number of ART cycles, embryo transfers, banking cycles, and live-birth deliveries from 2011–2020
→ These graphs show a clear upward trend.

A slide titled the number of infants conceived using ART (2011–2020)
→ Shows ART infants rising over time.

Slide showing percentage of cycles using single embryo transfer (2011–2020)
→ Trend shows major increase over time.

A figure showing the percentage of embryo transfer cycles resulting in singleton, twin, and triplet+ live births (2011–2020)
→ Singletons ↑, multiples ↓ → exactly what I summarized.

reasons for ART cycles

egg or embryo banking, other related reasons to infretility, male factor infertility, diminished ovarian reserve, preimplantation genetic testing, ovulatory dysfunction, tubal factor, unexplained factor, endormetriosis

gestational carrier is the lowest

art for family building

most common 35-39

ART age effect

• Age is the strongest predictor of ART success, particularly when using one’s own eggs.

• Live-birth rates are highest for women under 35, decline in the 35–37 range, decline more steeply at 38–40, and become very low after age 40.

• For women in their early 40s, IVF failure rates exceed 85% per cycle (CDC).

• Even for women under 35, failure rates exceed 60% per cycle.

• Success rates with donor eggs stay relatively stable across all ages, showing that the limiting factor is egg quality, not uterine age.

• Because egg quality declines sharply with age, ART cannot fully compensate for delayed childbearing.

ART timing

Key takeaway: ART provides limited compensation for age-related fertility decline.

• Before 35: “Be patient” — spontaneous conception rates are high.

• After 35: “Be impatient” — chances decline quickly, and ART does not restore lost time.