ICU · Obstetric critical care

Physiology of Pregnancy Relevant to the ICU

Also known as Pregnancy physiology · Maternal physiology · Pregnancy physiological adaptations · Supine hypotensive syndrome · Pregnancy acid-base · Hypercoagulability of pregnancy · Aortocaval compression

Pregnancy triggers profound physiological adaptations relevant to the ICU — cardiovascular (cardiac output rises from early pregnancy, heart rate first then stroke volume, plateauing by midpregnancy while vascular resistance falls; supine aortocaval compression typically after 20 weeks mandating left lateral tilt), respiratory (progesterone-driven rise in minute ventilation and tidal volume producing a compensated respiratory alkalosis with low PaCO2 and raised arterial pH, a reduced FRC with rapid desaturation, and failed intubation in about 1 in 390 obstetric general anaesthetics), renal (renal plasma flow and GFR rise on early-gestation systemic vasodilation), and haematological (a venous thromboembolism relative risk of 4.29 versus non-pregnant women, with falling fibrinogen predicting severe postpartum haemorrhage). Understanding the pregnancy baseline is essential to safe ICU management.