Twin Birth and Hemolysis, Elevated Liver Enzymes, and Low Platelets (HELLP) Syndrome: A Population-Based Study

Although twin pregnancies are known to have higher rates of preeclampsia, the association between twin pregnancy and Hemolysis, Elevated Liver Enzymes, and Low Platelet Count (HELLP) syndrome has not been adequately studied. We assessed the association between twin pregnancy and HELLP syndrome, and also examined gestational age-specific rates of HELLP syndrome in twin and singleton pregnancies.

We conducted a retrospective cohort study of women with singleton or twin live births or stillbirths between 20⁰ and 43⁶ weeks gestation in British Columbia, Canada, from 2008/09 to 2019/20. Data on the demographic and clinical characteristics were obtained from the British Columbia Perinatal Database Registry. Logistic regression was used to estimate adjusted odds ratios and 95% CIs, adjusted for maternal age, body mass index, smoking, and other potential confounders.

Among 524 236 women (515 953 singleton and 8283 twin pregnancies), 1510 were diagnosed with HELLP syndrome (2.9 per 1000 women). HELLP syndrome occurred in 181 twin pregnancies (21.9 per 1000 women), while 1329 cases occurred in singleton pregnancies (2.6 per 1000 women) (rate ratio 8.5 [95% CI 7.3-9.9]). The adjusted odds ratio for the associations between HELLP syndrome and twin versus singleton pregnancies was 7.1 (CI 6.0-8.5). In twin pregnancies, the incidence of HELLP syndrome increased markedly from 26⁰ to 28⁶ weeks gestation until 37⁰ to 39⁶ weeks. In contrast, the incidence of HELLP syndrome increased more gradually from 23⁰ to 40⁶ weeks gestation in singleton pregnancies.

Twin pregnancy is strongly associated with HELLP syndrome. HELLP syndrome risk in twin pregnancies increases markedly from 26⁰ weeks gestation onwards.