Sex and Childbirth

4 phases of sexual intercourse

1. Excitement

   • engorgement of blood vessels and cardiovascular changes

2. Plateau

   • sexual flush to face and chest

3. Orgasm (climax)

   • rhythmical muscular contractions and pleasure

   • sympathetic nervous system causes ejaculation

4. Resolution

   • profound relaxation and return to normal

   • male refractory period where 2nd ejaculation is impossible

Pregnancy and Childbirth

• Gestation (pregnancy) lasts an average of 266 days from conception to childbirth

• Birth is predicted to occur 280 days from LMP

Changes during Pregnancy

Cardiovascular → Rise in cardiac output of 20-30%, HR 15% blood volume 30-50%

Respiratory → Increase in tidal volume and MV by 40%

Urinary → Water retention, GFR increases by 50%, frequent urination

Integumentary → Linea nigra and chloasma, stretch marks

Reproductive system → uterus increases in size from 80g to 1200g

Human chorionic gonadotropin (Hcg)

• secreted by the early embryo can be detected 8-10 days after fertilization

• protects corpus luteum (if it degrades lining will shed)

Estrogens produced by fetus and placenta

• greatly increase during pregnancy

• stimulates tissue growth

• relaxes pelvis, public symphysis, sacroiliac joint

Progesterone produced by fetus and placenta

• with estrogen, inhibits FSH and LH release (prevents ovulation during pregnancy)

• suppresses uterine contractions

• protects uterine lining

No progesterone will cause spiral arteries to constrict and lining will shed to begin menstruation.

Human chorionic somatomammotropin

• shifts maternal metabolism to glucose-sparing (saving it for embryo)

• mother runs off of fatty acids to preserve glucose for fetus

ACTH

needed for lung maturation

• allows baby’s lungs to produce surfactant

Parturition

Process of giving birth by means of contraction of mother’s uterine and abdominal muscles

Progesterone inhibits uterine contractions

Estrogen stimulates contractions

Near full term

• Increased oxytocin

• Uterus produces more oxytocin receptors

  • directly stimulates myometrial contractions

  • stimulates fetal membranes to produce prostaglandins which are synergists of oxytocins

• Fetus secretes cortisol, enhancing estrogen secretion and oxytocin stimulating prostaglandin secretion

True vs False Labor

• True labor begins when contractions occur at regular intervals

  • produces pain

  • back pain increases with walking

  • dilation of cervix with discharge of mucus in cervical canal

• False labor produces pain at irregular intervals but there is no cervical dilation

Labor Contractions

• contractions begin 30 minutes apart and eventually occur every 1-3 minutes

  • periodically relax to increase blood flow to placenta (fetus)

  • contractions strongest in the fundus and body pushing fetus to cervix

• Self-amplifying cycle of stretch and contraction (reflex)

  • postive feedback cycle increasing contractions

  • cervical stretching → oxytocin secretion → uterine contraction → cervical stretching

  • 2nd reflex arc is from uterus → spinal cord → abdominal sk muscles producing contractions that help expel fetus

• Pain of labor is ischemia of myometrium, stretching of cervix, vagina and perineum (episiotomy prevent tearing)

Stages of Labor

1. Early Dilation:

   • widening of cervical canal by thinning of the cervix to reach 10cm— deameter of fetal head

   • rupture of fetal membrane and loss of amniotic fluid

2. Late Dilation:

   • Dilation reaches 10cm in 24 hours or less in first baby and in as little as a few minutes with multiple children

3. Expulsion:

   • Time from when baby’s head reaches vagina and until delivery

   • Valsalva maneuver helps to expel fetus

4. Crowning:

   • Head reaching the vulva

5. Emergence:

   • Baby’s head exits canal

6. Placental Stage:

   • Uterine contractions continue causing placental separation

   • 350mL blood loss

7. Afterbirth passing

Dystocia

• Difficult labor due to fetal position or size

• breech presentation is butt of feet first

Puerperium

• First 6 weeks after delivery

• Mothers anatomy and physiology return to normal

  • uterus shrinks called involution

  • breastfeeding promotes involution

Development of mammary glands

Lactation = synthesis and ejection of milk from mammary glands

High estrogen levels in pregnancy cause ducts to grow and branch

Progesterone stimulates budding and development of the acini at the ends of ducts

→ e2 and p4 build the machinery for milk synthesis and ejection but inhibit the actual production of milk

Colostrum and Milk Synthesis

• colostrum → nutrition for first 1-3 days after birth, contains immune antibodies, and 1/3 less fat

• synthesis is promoted by prolactin (from pituitary)

• at birth, prolactin secretion drops to non-pregnant levels but increases with nursing events

• prolactin inhibits GnRH

Milk Ejection

• controlled by neuroendocrine reflex

  • infant’s suckling stimulates sensory receptors in nipple, signaling hypothalamus and posterior pituitary to release oxytocin

  • oxytocin stimulates myoepithelial cells that squeeze glands and pushes milk out

  • oxytocin released by baby crying

Endometriosis

Endometrial tissue grows outside uterus and is unable to shed via normal pathway → painful and can cause infertility

Adenomyosis

endrometrial tissues appear inside the myometrium

cervical cancer

• starts as cervical dysplasia (change in shape, growth, and number of cells)

• may progress to cervical cancer

• detected in pap smear

• linked to genital warts, herpes, large number of sexual partners at early age