(HealthDay)—Polycystic ovary syndrome (PCOS) diagnosis is associated with increased risk of preterm delivery in twin pregnancies, according to a study published in the September issue of BJOG: An International Journal of Obstetrics and Gynaecology.

Tone S. Løvvik, M.D., from the Norwegian University of Science and Technology in Trondheim, and colleagues conducted a population-based cohort study in Sweden involving 20,965 women with twin births between 1995 and 2009, of whom 226 had a PCOS diagnosis. The authors investigated pregnancy and for women with and without PCOS.

The researchers found that PCOS diagnosis in correlated with increased preterm delivery risk (51 versus 43 percent; risk ratio, 1.18). Risk was particularly elevated for spontaneous preterm delivery (37 versus 28 percent; risk ratio, 1.3) and very preterm birth (14 versus 8 percent; risk ratio, 1.62). Low birth weight occurred more often among twins of PCOS mothers (48 versus 39 percent; adjusted risk ratio, 1.4). After adjustment for gestational age, this difference did not persist. The risk for cesarean section, pre-eclampsia, low five-minute Apgar score, or perinatal mortality did not differ between the two groups.

"The risk of in twin pregnancies is increased by having a PCOS diagnosis," the authors write. "This should be considered in risk estimation and antenatal follow-up of twin pregnancies."