Maternal physiology

Question 1

What are the endocrine changes in pregnancy mediated by?

Answer 1

Increased placental steroid hormonal production - especially increases in oestrogen and progesterone

Others: prolactin, HPL (human placental lactogen), PTH, cortisol, aldosterone

Question 2

What are cardiovascular changes during pregnancy?

Answer 2

Increase:
- blood volume (40-50%)
- heart rate
- stroke volume
- cardiac output (x 50% 1st trimester)

Decrease:
- peripheral vascular resistance
- blood pressure (causes dizziness, orthostatic hypotension etc)

Question 3

What are haematological changes in pregnancy?

Answer 3

Increase
- plasma volume (50%)
- red cell (20-30%)
- procoagulants (vWF, fibrinogen, VIII, X)
- white cell count (up to 16)
Decreases
- haematocrit (relative)
- thrombocytopaenia (lower end normal 100-150)

Question 4

What are skin changes in pregnancy?

Answer 4

Increase in pigmentation:
- linear nigra, chloasma
- striations (striae gravidarum)
- vascular changes - spider navei, palmer erythema, venous varicosities

Dermatoses:
- prutitis
- PEP - polymorphic eruption of pregnancy
- pemphigoid gestationalis

Question 5

What are gastrointestinal changes in pregnancy?

Answer 5

Early pregnancy nausea + vomiting (HcG mediated) (Hyperemesis gravidarum if severe)

Decreased gastric emptying (pro emetic)

Relaxation gastro-oesophageal sphincter tone (reflux)

Decreased colonic motility (constipation)

Haemorrhoids

Biliary stasis - progesterone mediated, LFTS no change

Question 6

What are renal changes in pregnancy?

Answer 6

Increase blood flow - increase kidney/ureter size, physiological hydronephrosis

Increased GFR (+50%) - glycosuria, albuminuria

Plasma decrease urea, creatinine, increase urine stasis (UTI)

Up-regulation of renin-angiotensin-aldosterone system

Question 7

What are genital changes in pregnancy?

Answer 7

Uterus – progressive increase in size until 36-38 weeks
- Hypertrophy / hyperplasia / muscle stretching)
- 900-1000 gms at term
- Increased vascularity

Cervix –vascular, softer, bluish discolouration, bleeds more easily. Increased secretions. Mucus plug seals cervical canal

Vagina / vulva –oedematous, hyperaemic, secretions, varicosities. Vaginal pH more acidic (lactobacilli)

Question 8

What are metabolic changes in pregnancy?

Answer 8

Increased protein metabolism and deposition (fetal, placental, maternal tissue) - up to 1kg extra protein deposited

Total weight gain (IDEAL) not more than 12.5 kg (often less is safer and recommended)

Increased carbohydrate metabolism, insulin resistance

Question 9

What are respiratory changes in pregnancy?

Answer 9

Increased minute ventilation (progestogen effect on bronchiolar smooth muscles) - respiratory alkalosis, metabolic acidosis (pH slightly higher in pregnancy)

Increased O2 requirement (up to 20%)

Reduced RV and FRC due to upwards displacement of the diaphragm – may be associated with exacerbation of pre-existing respiratory disease

Question 10

What are musculoskeletal changes in pregnancy?

Answer 10

Joint, soft tissue remodelling

Relaxation of sacroiliac joints and symphysis pubis - facilitates vaginal delivery but may be lead to discomfort

Changes in posture, balance & gait

Lordosis – keep centre of gravity over the legs, back pain, unsteadiness of gait and proneness to falls