Is there merit in treating gestational diabetes mellitus?

Design: Pregnant women between 16 and 30 weeks of gestation at 18 collaborating centres were screened for insulin intolerance. Those having 1 or more risk factors for gestational diabetes or who had results from a 50-g oral glucose challenge test (defined as ≥ 7.8 mmol/L at 1 h) underwent a 75-g oral glucose tolerance test at 24–34 weeks’ gestation. Healthy women with a fasting plasma-glucose measurement below 7.8 mmol/L but a 2-hour result of 7.8–11 mmol/L were eligible for the study. Women with more severe glucose intolerance were excluded. After randomization, women in the intervention group (n = 490) were given dietary counselling, were taught how to selfmonitor glucose and received insulin therapy as needed to maintain fasting and premeal plasma glucose concentrations below 5.5 mmol/L. The women in the control group (n = 510) received the care routinely given when screening for gestational diabetes is unavailable. These women (or their physicians) were told that they did not have gestational diabetes. Primary outcomes among infants were serious perinatal complications (death, shoulder dystocia, bone fracture or nerve palsy), admission to the neonatal nursery and jaundice requiring phototherapy. The primary maternal outcomes of interest were induced labour, cesarean section and mental health scores (measured with the 36-item ShortForm General Health Survey, the short Spielberger State– Trait Anxiety Inventory and the Edinburgh Postnatal Depression Scale). All statistical analyses were based on intention to treat.