HELLP syndrome, risk factors in first and second pregnancy: a population-based cohort study

HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count) may have specific risk factors and risk factors varying from first to second pregnancy. The aims of the study were to estimate the risk of HELLP syndrome by potential risk factors in first and second pregnancy, respectively.

A population-based cohort study including all women in Norway having their first baby (≥22 gestational weeks) during 1999 to 2014, registered in the Medical Birth Registry (n = 418 897). A subset of women with at least two births (n = 249 070) was used for estimates in second pregnancy. Relative risks with 95% CIs for HELLP syndrome were estimated using logistic regression and adjusted for maternal age and year of childbirth.

Body mass index ≥30 kg/m² and diabetes were associated with HELLP syndrome in first, but not in second pregnancy. Chronic hypertension and multiple pregnancy were associated with HELLP syndrome both in first and second pregnancy. In second pregnancy the strongest risk factors were a history of HELLP syndrome or preterm preeclampsia in the first. The risk was inversely correlated with gestational age at first delivery. The overall relative risk for recurrence of HELLP syndrome was 54.4 (95% CI 34.3-86.2) and 129.5 (95% CI 45.7-367.2) after HELLP syndrome before 29 weeks of gestation in first pregnancy.

Important risk factors for HELLP syndrome differ from first to second pregnancy. HELLP syndrome in second pregnancy is rare, but the relative risk is very high in women with HELLP syndrome or preterm preeclampsia in their first pregnancy.