Supine Hypotension Syndrome

Pathophysiology

The enlarged gravid uterus compresses the inferior vena cava when the patient lies supine, particularly after 20 weeks of gestation, decreasing venous return to the heart and subsequently reducing cardiac output 1, 2
This aortocaval compression can decrease cardiac output by up to 24% at 32 weeks gestation when supine compared to the left lateral position 1

The immediate improvement with position change (sitting up) confirms the diagnosis, as this relieves inferior vena cava compression and restores venous return 1, 2
Pregnant patients after 20 weeks gestation should avoid prolonged supine positioning during procedures, examinations, or sleep 2, 4
The left lateral position or left pelvic tilt should be maintained during endoscopic procedures, imaging studies, and any prolonged recumbent positioning to prevent aortocaval compression 2

Option C (Orthostatic hypotension) is incorrect because orthostatic hypotension causes blood pressure to drop when moving from lying to sitting/standing positions, whereas this patient's blood pressure increases when sitting up 3