OBJECTIVE: To estimate the association between gestational diabetes mellitus (GDM) and adverse pregnancy and neonatal outcomes in Denmark.

METHODS: A population-based cohort study including all singleton pregnancies in Denmark from 2004 to 2010 (n = 403 092). Maternal complications during pregnancy and delivery and fetal complications were classified according to the International Classification of Diseases 10th Revision.

RESULTS: The final study population consisted of 398 623 women. Of these, 9014 (2.3%) had GDM. Data were adjusted for maternal age, parity, smoking, gestational age, birth weight, BMI, gender of the fetus and calendar year. The risk of preeclampsia, caesarean section (both planned and emergency) and shoulder dystocia was increased in women with GDM. In the unadjusted analysis, the risk of thrombosis was increased by a factor 2 in the GDM patients, but in the adjusted analysis this association disappeared. Post-partum hemorrhage was similar in the two groups. The GDM women had an increased risk of giving birth to a macrosomic neonate although the unadjusted analysis did not show any difference between the two groups. Low Apgar score was increased in the GDM, but this association disappeared in the adjusted analysis. Stillbirth was comparable in the two groups.

CONCLUSIONS: Women with GDM still have increased incidence of obstetric and neonatal complications, which could imply that treatment of women with GDM should be tightened.