The HYPITAT trial (2009) compared induction of labour versus expectant management in women with gestational hypertension or mild pre-eclampsia at 36–41 weeks. The primary composite outcome of adverse maternal outcomes was significantly reduced in the induction group. Which of the following best describes the mechanism by which immediate delivery reduces maternal risk in near-term pre-eclampsia?

• A Delivery stops progesterone-mediated peripheral vasodilation that worsens hypertension
• B Delivery prevents placental abruption by eliminating Braxton-Hicks contractions
• C Delivery removes the source of excess sFlt-1 and soluble endoglin, reversing endothelial dysfunction ✓
• D Delivery eliminates fetal production of thromboxane A2 that causes maternal platelet aggregation

Explanation

The placenta is the primary source of anti-angiogenic factors sFlt-1 (soluble fms-like tyrosine kinase-1) and soluble endoglin, which sequester VEGF and PlGF and TGF-β1 respectively, impairing maternal endothelial repair and causing systemic endothelial dysfunction. Delivery removes this pathological placental tissue, allowing sFlt-1 and sEng levels to fall and endothelial function to recover — the only definitive cure. Progesterone causes peripheral vasodilation which actually buffers hypertension; thromboxane A2 is primarily of platelet/endothelial origin; and Braxton-Hicks contractions do not cause abruption.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.