Physiological Changes In Pregnancy

Question 0

Genital changes

Answer 0

Uterus increases from 100g to 1100g
- muscle hypertrophy up to 20wks then stretches

Cervix may develop ectropion.

Vaginal discharge increases due to cervical ectopy, cell desquamation, increased mucus production from vasocongested vagina.

Question 1

Hormonal changes

Answer 1

Progesterone

• made by corpos luteum until day 35 then made by placenta
• decreases smooth muscle excitability (uterus, gut, ureters)
• raises body temperature

Estrogen

• increases breast and nipple growth
• increases water retention
• increases protein synthesis

Pituitary secretion of prolactin rises throughout pregnancy.

Cortisol output is increased but unbound levels remain constant.

Question 2

Haemodynamic changes

Answer 2

Blood:

• plasma volume rises to 50% > non pregnant
• red cell volume rises by 30% (w/iron)
• Hb falls due to dilution (physiological anaemia)
• WCC, platelets, ESR, cholesterol, fibrinogen all raised
• albumin, urea, creatinine all fall

Cardiovascular:

• cardiac output increases
  
  • stroke volume increases 10%
  • pulse increases by 15
• peripheral resistance falls
• BP (esp diastolic) falls in second trimester by 10-20 then rises to non-pregnant levels by term
• varicose veins may form (due to increased venous distensiblity and increased venous pressure from pelvic mass)
• vasodilation and hypotension stimulate renin and angiotension release

Aorto-caval compression

• from 20wks due to uterus on IVC
• reduces cardiac output by 30-40% (supine hypotension)
• placing in left lateral position restores cardiac output

Question 3

Respiratory

Answer 3

Ventilation increases 40%

Tidal volume increases from 500 to 700

O2 consumption increases 20%

Breathlessness common as maternal PaCO2 set lower to allow fetus to offload CO2

Question 4

GI

Answer 4

Reduced gut motility (constipation)

Delayed gastric emptying

Heart burn due to lax cardiac sphincter

Question 5

Urinary

Answer 5

Kidneys increase 1cm in length

Frequency

• GFR increased by 60% (early)
• bladder pressure from fetus (late)

Question 6

Skin

Answer 6

• linea nigra
• nipple pigmentation
• chloasma
• palmar erythema
• spider navei
• striae

Hair shedding reduced in pregnancy but extra hairs shed in puerperium.

Question 7

Recommended total weight gain (singleton)

Answer 7

Roughly 10kg, more if lower BMI, less if higher BMI