Maternal, Feto-Placental and Neonatal Transitional Physiology — WACS Viva & Clinical Scenarios (Physiology and Applied Physiology)

Exam-style maternal, feto-placental and neonatal transitional physiology viva scenarios with examiner probes and model answers for ANAESTHESIA candidates.

Scenarios covered

• SCENARIO 1: A 30-year-old at 38 weeks gestation is scheduled for emergency Caesarean section under general anaesthesia. Describe the maternal cardiovascular and respiratory physiological changes of pregnancy at term, and explain why pregnant patients develop hypoxaemia much more rapidly during periods of apnoea compared to non-pregnant adults.
• SCENARIO 2: Draw a diagram of the Fetal Circulation. Trace the pathway of oxygenated blood from the placenta through the umbilical vein to the fetal heart, systemic organs, and back to the placenta. Describe the functional and anatomical roles of the Ductus Venosus, Foramen Ovale, and Ductus Arteriosus.
• SCENARIO 3: Describe the physiological mechanisms involved in the respiratory and cardiovascular transition from fetal to neonatal life immediately following birth. Detail the triggers that initiate the newborn first breath, the clearance of fetal alveolar fluid, and the factors responsible for the closure of the three fetal vascular shunts.
• SCENARIO 4: Compare and contrast the respiratory physiology of a healthy full-term neonate with that of a healthy 25-year-old adult. Structure your answer around: lung and chest wall compliance, Functional Residual Capacity and Closing Capacity, oxygen consumption (VO₂), alveolar ventilation, control of breathing, and diaphragmatic muscle fibre composition.
• SCENARIO 5: Explain the physiology of gas and nutrient transfer across the human placenta. Detail the anatomical structure of the placental barrier, the determinants of Uteroplacental Blood Flow (UBF), and the specific roles of the Double Bohr effect and Double Haldane effect in facilitating fetal-maternal oxygen and carbon dioxide exchange.