Obs and Gynae Physiology

Question 1

What anterior pituitary hormonal changes happen in pregnancy?

Answer 1

• Increased ACTH, prolactin and melanocyte stimulating hormone in pregnancy.
• Higher ACTH levels cause more steroids (cortisol and aldosterone).
• Higher steroid levels lead to an improvement in most autoimmune conditions and a susceptibility to diabetes and infections.
• Increased prolactin acts to suppress FSH and LH
• Increased melanocyte stimulating hormone causes increased pigmentation of the skin during pregnancy, linea nigra and melasma.
• TSH remains normal, but T3 and T4 levels rise.

Question 2

What happens to progesterone during pregnancy? What does progesterone do? What produces progesterone?

Answer 2

Progesterone levels rise throughout pregnancy. Progesterone acts to maintain the pregnancy, prevent contractions and suppress the mother’s immune reaction to fetal antigens.

The corpus luteum produces progesterone until ten weeks gestation. The placenta produces it during the remainder of the pregnancy.

Question 3

What happens to HCG after fertilisation?

Answer 3

HCG levels rise, roughly doubling every 48 hours until they plateau around 8 – 12 weeks, then gradually start to fall.

Question 4

What happens to oestrogen levels in pregnancy and what produces it?

Answer 4

Oestrogen rises throughout pregnancy, produced by the placenta.

Question 5

What changes happen to the uterus, cervix and vagina in pregnancy?

Answer 5

• The size of the uterus increases from 100g to 1.1kg during pregnancy.
• There is hypertrophy of the myometrium and the blood vessels in the uterus. Increased oestrogen may cause cervical ectropion and increased cervical discharge.
• Oestrogen also causes hypertrophy of the vaginal muscles and increased vaginal discharge as preparation for delivery but make bacterial and candidal infection (thrush) more common.
• Before delivery, prostaglandins break down collagen in the cervix, allowing it to dilate and efface during childbirth.

Question 6

What resp changes occur in pregnancy?

Answer 6

increased subcostal angle
increased pulmonary blood flow
increased tidal volume
decreased vital capacity
decreased functional residual capacity
increased DPG

Hyperventilation is often experienced - maybe because of increased CO2 and progesterone increases resp drive so respiratory alkalosis with a compensated increase in renal bicarbonate excretion.

Question 7

What happens to blood volume and plasma volume in pregnancy?

Answer 7

Both are increased

Question 8

What happens to cardiac output in pregnancy?

Answer 8

Increased CO with increased SV and HR

Question 9

What happens to peripheral vascular resistance in pregnancy?

Answer 9

decreased

Question 10

How does blood pressure change during pregnancy?

Answer 10

Decreased blood pressure in early and middle pregnancy, returning to normal by term

Question 11

Why may pregnant women develop varicose veins?

Answer 11

can occur due to peripheral vasodilation and obstruction of the inferior vena cava by the uterus

Question 12

Why may pregnant women experience hot flushes and sweating?

Answer 12

Peripheral vasodilatation

Question 13

What happens to blood flow to the kidneys and GFR in pregnancy?

Answer 13

Both increase

Question 14

What happens to aldosterone in pregnancy and what does this do?
What happens to protein excretion in pregnancy?

Answer 14

Increased aldosterone leads to increased salt and water reabsorption and retention
Increased protein excretion from the kidneys (normal is up to 0.3g in 24 hours)

Question 15

What cause physiological hydronephrosis in pregnancy?

Answer 15

Dilatation of the ureters and collecting system, leading to a physiological hydronephrosis (more right-sided)

Question 16

What effect does progesterone have on the urinary system?

Answer 16

Progesterone affects the urinary collecting system causing relaxation of the ureter (resulting in hydroureter) and relaxation of the muscles of the bladder. Both of these changes causes urinary stasis which predisposes a woman to UTIs, commonly pyelonephritis.

Question 17

What skin and hair changes are seen in pregnancy?

Answer 17

Increased skin pigmentation due to increased melanocyte stimulating hormone, with linea nigra and melasma
Striae gravidarum (stretch marks on the expanding abdomen)
General itchiness (pruritus) can be normal, but can indicate obstetric cholestasis
Spider naevi
Palmar erythema
Postpartum hair loss is normal, and usually improves within six months.