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NZ Midwifery Registration study materials
NZ Midwifery Registration study resources

NZ Midwifery Registration: Midwifery knowledge: anatomy, physiology and pathophysiology

NZ Midwifery Registration · Work through your exam, one topic at a time.

All guide sections

Midwifery knowledge: anatomy, physiology and pathophysiology

This section covers the anatomy, physiology and pathophysiology of pregnancy, labour, birth and the postnatal period. The exam tests whether you can link structure and function to clinical findings and recognise when normal adaptation becomes pathology.

Normal adaptation

  • Plasma volume rises 40–50% by 32–34 weeks; red cell mass rises less, producing dilutional anaemia.
  • Cardiac output increases 30–50%; blood pressure falls in the second trimester, with a nadir around 20–24 weeks, then rises.
  • After 20 weeks, supine position compresses the inferior vena cava; left lateral positioning improves venous return.
  • Minute ventilation rises through increased tidal volume, giving compensated respiratory alkalosis and normal dyspnoea.
  • Pregnancy is hypercoagulable: fibrinogen and clotting factors rise and fibrinolysis falls.
  • GFR rises about 50%, so creatinine falls; a creatinine within the non-pregnant "normal" range may be abnormal in pregnancy.

Pathophysiology to recognise

  • Pre-eclampsia: abnormal spiral artery remodelling and trophoblast invasion cause endothelial dysfunction; hypertension plus proteinuria OR maternal organ dysfunction (thrombocytopenia, renal, liver, neurological, pulmonary oedema).
  • Gestational diabetes: human placental lactogen and other hormones cause insulin resistance.
  • Postpartum haemorrhage: tone, trauma, tissue, thrombin.
  • Labour: fundal dominance, retraction and the Ferguson reflex drive progress; placental separation occurs through the spongiosa layer, with Schultze or Matthews Duncan patterns affecting bleeding.

Worked example

At 34 weeks a woman has BP 150/100, platelets 90 and ALT twice normal, with no proteinuria. This still meets pre-eclampsia criteria because organ dysfunction alone is sufficient. The correct action is escalation and close monitoring, not waiting for protein to appear.

Traps

Dismissing second-trimester blood pressure as normal; confusing physiological dyspnoea with pulmonary oedema; interpreting a low creatinine as renal health.