Endocrine Abstracts

Introduction: Gestational diabetes mellitus (GDM) is a common condition of pregnancy, associated with significant maternal and fetal complications. Debate surrounds screening practices, without worldwide consensus on the optimal screening method. Both the one-step (a fasting two-hour 75g oral glucose tolerance test) and two-step (a non-fasting one-hour 50g glucose challenge test followed, if positive, by a fasting three-hour 100g glucose tolerance test) methods are internationally acceptable screening tests.

Methods: We evaluated incidence of GDM alongside maternal and fetal pregnancy outcomes in two centres where risk-factor based GDM screening is performed using these different methods.

Results: 963 participants were recruited and underwent screening for GDM using the one-step (n = 531) and two-step methods (n = 432). Mean (±SD) age was slightly lower in the one-step group at 33.9 (4.9) years vs 36.1 (4.8). In both groups, most participants were Caucasian (80% and 86%). Mean BMI was 28.6kg/m ² (6) and 27.4 (6.2). The incidence of GDM was higher in the one-step group (19.0% vs 13.7%, P = 0.027). Data collection is in progress, with completed outcomes data available on 240 and 350 participants in the one-step and two-step groups, respectively. On review of preliminary data, mean delivery gestation was 38.7 (1.5) and 38.7 (1.7) weeks. Pre-term birth rates (delivery before 37 weeks’ gestation) were 4.6% and 7.7%. Rates of Caesarean section did not differ, at 44.2% and 44.3%. Mean birth weights were similar; 3.52kg (0.53) vs 3.52kg (0.55). The incidence of macrosomia (defined as birth weight >4kg) was also comparable, at 17.1% in both groups. Rates of small for gestational age (birth weight <10 ^th centile) were 4.6% and 3.4%. Fetal complications were very rare in both groups.

Conclusion: In our study population, the incidence of GDM was higher in those tested using the one-step method. Maternal and fetal outcomes were similar between groups.