Pregnancy and perinatal outcomes in women with polycystic ovary syndrome and twin births: a population-based cohort study

ObjectiveTo investigate pregnancy and perinatal outcomes in twin births among women with and without polycystic ovary syndrome (PCOS) diagnosis. DesignPopulation-based cohort study. SettingSweden. PopulationWe identified 20965 women with twin births between 1995 and 2009 of whom 226 had a PCOS diagnosis through linkage between the Swedish Medical Birth Register and the Swedish National Patient Register. MethodsCalculating risk ratios (RR) with 95% confidence intervals (CI) using a log-binomial regression model and hazard ratios (HR) with 95% CI for preterm birth. Main outcome measuresPreterm birth, low birthweight, caesarean section, pre-eclampsia, Apgar score <7 at 5minutes and perinatal mortality. ResultsPCOS diagnosis in twin pregnancy was associated with increased risk of preterm delivery (51% versus 43%, RR 1.18 [95% CI 1.03-1.37]), particularly spontaneous preterm delivery (37% versus 28%; RR 1.30 [95% CI 1.09-1.55]) and very preterm birth (<32weeks) (14% versus 8%, RR 1.62 [95% CI 1.10-2.37]). Twins of PCOS mothers had more often low birthweight (48% versus 39%, adjusted RR 1.40 [95% CI 1.09-1.80]). This difference disappeared when adjusting for gestational age. No risk difference was found for caesarean section, pre-eclampsia, low 5-minute Apgar score or perinatal mortality. ConclusionsThe risk of preterm delivery in twin pregnancies is increased by having a PCOS diagnosis. This should be considered in risk estimation and antenatal follow-up of twin pregnancies.