Reproduction VI: Pregnancy & Contraception

Question 1

The placenta does not express which gene/enzyme?

Answer 1

CYP17 (17α-hydroxylase), so placenta cannot convert past progesterone

Question 2

What are the 3 main functions of the placenta?

Answer 2

1. Support (provides nutrients)
2. Immune (prevents rejection of fetus by mother)
3. Endocrine (synthesizes hormones)

Question 3

Which hormone produced by syncytiotrophoblasts are GH-like and prolactin-like?

Answer 3

hPL (human placental lactogen) - counter-regulatory to insulin, mobilizes glucose for fetal use, stimulates mammary gland development

Question 4

What are the risk factors for gestational diabetes?

Answer 4

• women >25 years old
• family Hx of diabetes
• belonging to certain ethnic groups (ex: Native Americans)

Question 5

What happens to cortisol in the placenta?

Answer 5

It is inactivated by 11β-HSD (type 2), which converts it to cortisone. This protects the fetal adrenal axis from maternal cortisol.

Question 6

What is the function of relaxin in pregnancy?

Answer 6

It inhibits myometrial contractions to ensure uterine quiescence in early pregnancy, and it relaxes pelvic bones/ligaments.

Question 7

What is the function of prolactin in pregnancy?

Answer 7

It is essential for

Question 8

How much more protein per day is required to sustain growth of the fetus?

Answer 8

30g

Question 9

During pregnancy, the HPG axis is suppressed by what?

Answer 9

high concentrations of placental sex steroids

Question 10

How does a woman’s metabolism change throughout pregnancy?

Answer 10

• first half: anabolic state with normal or increased sensitivity to insulin; allows mother to “stockpile” nutrients to meet demands of fetus
• second half: catabolic state characterized by insulin resistance; mediated by hPL; increased plasma glucose and fatty acids

Question 11

What are the stages of labor?

Answer 11

Phase 0: quiescent uterus kept inactive, mainly by progesterone
Phase 1: Activation of uterus
Phase 2: Positive feedback phase
Phase 3: Evacuation of uterus

Question 12

What is the Ferguson reflex?

Answer 12

happens during the first stage of labor; neuroendocrine reflex consisting of self-sustaining cycle of uterine contractions (mediated by oxytocin) initiated by pressure of fetus’s head at the cervix or vaginal walls

Question 13

The initiation/maintenance of labor and uterine evacuation are influenced MOST by:

Answer 13

decrease in progesterone and increase in estrogen

Question 14

How does uterine sensitivity to oxytocin change throughout pregnancy?

Answer 14

The uterus is insensitive to OT until 20 weeks. Sensitivity then gradually increases to 80 fold at 36 weeks, plateaus just before parturition, and increases to 200 fold in early labor.

Question 15

What is the synthetic form of oxytocin used to induce labor?

Answer 15

Pitocin

Question 16

True or false: maternal oxytocin initiates labor.

Answer 16

False! Oxytocin levels do not increase prior to labor, but it is released in bursts once labor begins with increased frequency as labor continues.

Question 17

What is responsible for initiation/activation of labor?

Answer 17

decrease in progesterone/estrogen ratio, leading to increased local prostaglandins

Question 18

In the last trimester, what are high cortisol levels in the fetus important for?

Answer 18

lung maturation! (increased pulmonary surfactant, lecithin)

Question 19

When is lactation initiated and what causes it?

Answer 19

initiated after delivery by decreased steroid hormones (progesterone and estradiol)

Question 20

What are the main functions of prolactin with regard to pregnancy?

Answer 20

-suppresses reproductive function by inhibiting GnRH
-stimulates maternal behavior during pregnancy and after parturition
(prolactin is also a lactogenic hormone, meaning it has mammogenic and galactogenic effects)

Question 21

What is the fundamental secretory unit of the breast?

Answer 21

alveolus

Question 22

What is colostrum?

Answer 22

the first breast milk produced, contains little fat

Question 23

Why are oral contraceptives good for controlling heavy periods (what is the mechanism)?

Answer 23

They induce glandular atrophy in the uterine endometrium.

Question 24

In oral contraceptives, what do progestational vs. estrogenic hormones do?

Answer 24

• progestational: prevent LH secretion and LH surge

- estrogenic: inhibit FSH release (also stabilize endometrium and potentiate progestin action)

Question 25

Why is the placenta considered an “imperfect” endocrine organ?

Answer 25

It lacks critical enzymes to complete many of the steps in steroid hormone biosynthesis. This helps protect the fetus from maternal steroids (like cortisol) and high gonadal steroid hormone levels.

Question 26

What CAN’T the placenta do?

Answer 26

• Synthesize cholesterol
• Convert progesterone to other steroids (lacks CYP17)
• Make enzymes required to make E3 (fetal liver makes the enzyme, CYP3A7)

Question 27

What is the main circulating estrogen during pregnancy?

Answer 27

estriol (E3)

Question 28

What are the 3 zones of the fetal adrenal cortex?

Answer 28

• definitive zone (becomes Z. glomerulosa)
• transitional zone (becomes Z. fasciculata)
• fetal zone (becomes Z. reticularis)

Question 29

True or false: prolactin comes from the placenta.

Answer 29

False - it comes from the maternal pituitary.

Question 30

How do MAP, pulmonary pressure, and venous pressure change during pregnancy?

Answer 30

• MAP decreases (TPR decr. more than CO incr.)
• pulmonary pressures stay the same (to offset incr. in blood vol.)
• venous pressure increases (150% venous distension)

Question 31

Is there a net increase or decrease in hematocrit during pregnancy?

Answer 31

net decrease; plasma and RBCs increase, but so does blood volume

Question 32

What are the respiratory changes that occur during pregnancy?

Answer 32

diaphragm is elevated to make room for the developing fetus; tidal volume will increase to compensate for decreased space

Question 33

What are the 2 main GI changes that happen during pregnancy?

Answer 33

• decreased GI motility to increase nutrient absorption (side effect=constipation)
• decreased LES tone, contributing to greater acid reflux

Question 34

Which two hormone have opposing effects during parturition?

Answer 34

progesterone and estrogen

Question 35

What are prolactin and oxytocin involved with in regard to breast milk?

Answer 35

oxytocin EJECTS breast milk (in response to neural input) and prolactin PRODUCES breast milk (in response to suckling of breast)