Clinical meaning
HELLP syndrome is a severe, life-threatening variant of preeclampsia characterized by three hallmark laboratory findings: Hemolysis (H), Elevated Liver enzymes (EL), and Low Platelets (LP). The syndrome typically develops after 27 weeks of gestation but can present as early as the second trimester or even postpartum (up to 7 days after delivery). HELLP affects approximately 0.5-0.9% of all pregnancies and 10-20% of pregnancies complicated by severe preeclampsia. The underlying pathophysiology begins with abnormal placentation. In a healthy pregnancy, trophoblast cells invade the spiral arteries of the uterus during the first trimester, remodeling these vessels from narrow, muscular arteries into wide, low-resistance channels that provide adequate blood flow to the developing placenta. In preeclampsia and HELLP, this trophoblastic invasion is incomplete, leaving the spiral arteries narrow and constricted. The resulting placental ischemia triggers the release of antiangiogenic factors (soluble fms-like tyrosine kinase 1, or sFlt-1) and inflammatory mediators into the maternal circulation. These substances cause widespread endothelial dysfunction -- the endothelial cells lining blood vessels throughout the maternal body become damaged and activated. Endothelial damage has three critical consequences that define...