Bio 27 November 19, 2012

1. Bio 27 November 19, 2012 Chapter 11: Conception, Pregnancy, and Childbirth

2. childbirth

3. Childbirth: a history • Most babies were born at home until the 1930s • Women were given general anesthesia for childbirth • Fathers not allowed in delivery rooms until the 1970s

4. Stages of childbirth • First-stage labor: dilation of the cervix to 10 centimeters • Bloody show: loss of cervical mucus plug • Breaking of water: amniotic sac breaks, usually due to uterine contractions • Can last for days, but usually 4–16 hours • Second-stage labor: cervix is fully dilated • Usually lasts 30 minutes–2 hours • infant descends into vaginal birth canal • Most women help with pushing

6. Delivery by cesarean section • Cesarean (or C-) section is when a baby is removed surgically through an incision in the abdomen & uterus • Recommended when • Fetal head is too large to pass through birth canal • Fetus gets “stuck” due to being feet-first (breech) or other problems • Maternal illness • Fetal distress, such as umbilical cord wrapped around the neck • Usually done under local anesthesia • In 1970, 5.5% of U.S. births were by C-section; in 2006 that number was 31%

7. after childbirth

8. Post-partum depression • 75% of mothers experience “post-baby blues” due to hormonal fluctuations (and maybe also lack of sleep!) • 15% of mothers experience post-partum depression, characterized by insomnia, anxiety, panic attacks, severe depression, and hopelessness; may lose interest in their babies

9. Breast-feeding • Soon after birth, a mother’s breasts will start producing a yellowish liquid called colostrum that contains antibodies and proteins • 1 to 3 days after birth, milk comes in; if a new mother does not nurse, it will stop being produced • Advantages of breast-feeding: it’s free, helps you lose pregnancy weight, contains helpful antibodies, enhances mother-child bonding • Disadvantages: requires physical proximity, some women find it uncomfortable or can’t produce milk

10. CHAPTER 12: SEXUALITY DURING CHILDHOOD & ADOLESCENCE

11. Sexual behavior during infancy & early childhood • Most people appear to be born with the capacity for sexual response • Many small children appear to masturbate, and some may even achieve orgasm (although not ejaculation for males) • Data on childhood sexuality are scarce! • Sexual behavior is a normal part of development • Hugging, kissing, and cuddling may be a way for children to learn to express positive feelings • Children deprived of “contact comfort” can have difficulty establishing intimate relationships later in life

12. Childhood masturbation • Infants and children may masturbate using their hands or objects like toys or pillows • In a 1998 study, 16% of mothers reported observing their 2-to 5-year-old children masturbating with their hands • Most parents discourage this, but telling children to stop rarely eliminates it • Children should be encouraged to only masturbate in private

13. Childhood sex play • Most likely to take place between ages 4–7 • Can be exhibition and rubbing of genitals, simulating intercourse, or other activities • Kinsey (1948, 1953) found that 45% of females and 57% of males reported participating in sex play by age 12 • Children may also act out heterosexual marriage roles “playing house” • Usually declines by age 8 or 9 when boys and girls typically play separately

14. the physical changes of adolescence & sexual behavior during adolescence

15. Physical changes of adolescence

16. Timing of puberty • Girls typically start puberty at age 10–11 and boys start around age 12 • Girls also start growing more quickly at the beginning of puberty than boys…thus, an average 12 year old girl is taller than an average 12 year old boy • Menarche typically occurs at age 12 or 13 • First ejaculation typically occurs in boys at around age 13; sperm typically do not appear in the ejaculate until around age 14

17. The sexual double standard • Seems to be diminishing somewhat in the U.S. although still prevalent • Males are under pressure to appear sexually experienced • Females are under pressure to appear sexy, but to be chaste in their behavior