Growth and Development 3: Maternal response to pregnancy

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How does the female body respond to pregnancy?

The maternal body must adapt to provide the environment, nutrients, waste removal, buoyancy and respiratory gasses for the developing embryo/foetus. Maternal changes to physiology include:

  1.   Metabolic Changes
  • hPL stimulates breast maturation and mammary gland preparation
  • hPL results in glucose-sparing effect, which affects lipid and carbohydrate metabolism, meaning glucose is reserved for the foetus
  • Increased appetite (10-30%)
  2.   Cardiovascular Changes
  • Blood volume increases 25-40%
  • Increased cardiac output
  • Decreased total peripheral resistance
  • Decreased blood pressure
  3.   Renal Changes
  • Enlarged kidneys
  • Dilated ureters
  • Increased urine production
  • 50% increase in glomerular filtration rate
  • Unregulated renin-angiotensin system → increases aldosterone levels → water and sodium retention
  4.   Respiratory Changes
  • Increased respiratory rate and tidal volume
  • Stimulated by increased blood flow
  • Oedema and congestion of nasal cavity
  • Dyspnea in late pregnancy due to inability for diaphragm to full contract
  5.   Gastrointestinal Changes
  • Morning sickness due to increased oestrogen and progesterone
  • Decreased motility
  • Smooth muscle relaxation by progesterone and relaxin
  6.   Mammary Gland Changes
  • hPL, placental prolactin, maternal prolactin, oestrogens, growth hormone and thyroxine cause mammary growth and development
  • After 6 months, glands produce colostrum
  • Milk production and lactation after birth
  7.   Uterine Changes
  • Starts out as 7.5cm, weighing 30-40g → 30cm long, weighing 1100g
  • Holds 2 litres of fluid as well as the foetus
  • Changes occur through hypertrophy of cells with enlarged smooth muscle fibres

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