Neonatal outcomes of twins <29 weeks gestation of mothers with hypertensive disorders of pregnancy

Background Hypertensive disorders of pregnancy (HDP) are associated with dysfunctional placentation and are a major cause of maternal and neonatal morbidity and mortality. Twin pregnancies have a larger placental mass and are a risk factor for HDP. The effect of HDP on neonatal outcomes in twin pregnancies is unknown. Methods Retrospective cohort study using the Canadian Neonatal Network database from 2010–2018 of twin infants <29 weeks gestation born to mothers with HDP and normotensive pregnancies. Using multivariable models, we determined adjusted odds ratios (AORs) and 95% confidence intervals (CI) for mortality, bronchopulmonary dysplasia, severe neurologic injury, severe retinopathy of prematurity (ROP), necrotizing enterocolitis, and nosocomial infection in twin infants of mothers with HDP compared to twin infants of normotensive mothers. Results Of the 2414 eligible twin infants <29 weeks gestational age, 164 (6.8%) were born to mothers with HDP and had higher odds of severe ROP (AOR 2.48, 95% CI 1.34–4.59). Preterm twin infants born to mothers with HDP also had higher odds of mortality (AOR 2.02, 95% CI 1.23–3.32). There was no difference in other outcomes. Conclusion Preterm twin infants <29 weeks gestation of HDP mothers have higher odds of severe ROP and mortality. Impact Hypertensive disorders of pregnancy, associated with placental dysfunction, are a major cause of maternal and neonatal morbidity and mortality. Twin pregnancy, associated with a larger placental mass, is a risk factor for hypertensive disorders of pregnancy. The effect of hypertensive disorders of pregnancy on outcomes of preterm twins is unknown. Preterm twins of mothers with hypertensive disorders of pregnancy are at higher risk of severe retinopathy of prematurity and mortality. Our data can be used to counsel parents and identify infants at higher risk of severe retinopathy of prematurity and mortality.