BACKGROUND: Although twin pregnancies are known to have higher rates of pre-eclampsia, the association between twin pregnancy and hemolysis, elevated liver enzymes and low platelets (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. METHODS: We carried out a retrospective cohort study including women with singleton or twin live birth or stillbirth between 20 and 43 RESULTS: Among 524236 women (515953 singleton and 8283 twin pregnancies), there were 1510 women 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 of 8.5 (95% CI 7.3-9.9). The aOR for HELLP syndrome was 7.1 (CI 6.0-8.5) comparing twin vs singleton pregnancies. In twin pregnancies, the incidence of HELLP syndrome increased markedly from 26 to 28 CONCLUSION: Twin pregnancy is strongly associated with HELLP syndrome. HELLP syndrome risk in twin pregnancies increases markedly from 26