o Cultural practices Preference for sons Slight general preference for gender selection of a girl, despite overlying preference for boys. Family size norms o Health Mortality rate Breastfeeding norms Breastfeeding tends to decrease fecundity. Proximate determinants o Biological constraints Time lost during pregnancy/ies You cannot get pregnant while you are pregnant. 9-10 months Time lost after delivery- postpartum infecundability 1.5 months (in general, without breastfeeding)
Waiting time to conception 7.5 months Probably much lower for women who are able to naturally conceive children. Time lost due to naturally occurring intra-uterine mortality- miscarriage Recommended 2 month waiting period [post-miscarriage] before returning to fertile state Much higher for people who do not realize they are pregnant beforehand Time lost due to sterility arising naturally (i.e., age) or induced by pathological condition (i.e., cancer) Variable depending on the individual Q: What is the practical maximum number of children a woman could have if she reproduced continuously from age 18-45 given the biological constraints? A: 15; Total fecundity o Behavioral constraints Extent of exposure to possibility of conception (e.g., time spent having sex) Breastfeeding Prolongs postpartum infecundability Prolactin suppresses ovulation [for an indeterminate amount of time]. Ovulation occurs approx. 2 weeks before period Contraceptive behavior/method Induced abortion Together, with the biological constraints, the behavioral constraints lower fertility to a total fertility of: 2-7 children. Q: Which of these factors the plays the greatest role in limiting fertility? o A: Contraception ° How does pregnancy happen? There is only one way: Sperm + egg = pregnancy When is pregnancy possible?
o Pregnancy is possible 10 days/month o Sperm can live 3-7 days in a woman’s body. o Eggs can live 1-3 days in a woman’s body. o Typically, women are considered most fertile for a period of about 3 days, right in the middle of their menstrual cycle. o A woman who has intercourse without using contraception has a 90% chance of becoming pregnant within a year. Preventing pregnancy o Two ways Preventing sperm penetration [via barriers (i.e., female condom, diaphragm, etc.)] Preventing egg release [via hormones] o Effectiveness of birth control (e.g., condoms, BCP, etc.) “Perfect use” means “used consistently and correctly”. “Typical use” means “not necessarily used consistently or correctly”. Pregnancies in the U.S. o Approximately 6.3 million births annually o Intended pregnancies: 52% o Unintended pregnancies: 48% Not necessarily “unwanted” (i.e., unexpected twins) Unintended pregnancies o Rates are highest among: Women ages 15-24 Unmarried women Women below 20% of the federal poverty level African American and Hispanic women o The small proportion of women who do not use contraceptives accounts for nearly half of all unintended pregnancies.
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- Spring '08
- Roe v. Wade, partner