Gestational diabetes mellitus (GDM) is a prevalent complication during pregnancy, posing significant risks to both the mother and the baby. It is associated with various adverse outcomes such as preeclampsia, obstetrical intervention, large-for-gestational-age neonates, shoulder dystocia, birth trauma, and neonatal hypoglycemia.
Timely screening and treatment for GDM, typically recommended between 24 to 28 weeks of gestation, have become essential to mitigate these risks. However, recent cohort studies have indicated that early hyperglycemia before 20 weeks gestation can lead to accelerated fetal growth and increased perinatal mortality compared to the diagnosis of GDM later in pregnancy.
Moreover, emerging evidence suggests a linear relationship between fasting glucose levels in early pregnancy and adverse pregnancy outcomes, highlighting the importance of early identification and management of GDM. To address this concern, it is recommended that women at high risk for diabetes undergo testing early in pregnancy to exclude undiagnosed diabetes. If glucose levels are elevated but fall below the diagnostic threshold for diabetes in nonpregnant adults, a diagnosis of early gestational diabetes is made, and treatment is initiated. However, the existing literature lacks robust data from randomized controlled trials demonstrating the benefits of early treatment for GDM.
A new randomized trial published in The New England Journal Of Medicine, has found that early treatment for gestational diabetes can lead to a lower incidence of adverse neonatal events compared to deferred or no treatment. The trial involved women who had a risk factor for hyperglycemia in pregnancy and were diagnosed with gestational diabetes before 20 weeks’ gestation based on WHO criteria. The results showed a significantly, albeit modestly, lower occurrence of a composite of adverse neonatal events in the group that received immediate treatment. The reduction in risk ranged from 1.2 to 10.1 percentage points, according to the 95% confidence interval.
Notably, the major contributor to the difference in outcomes was a lower incidence of neonatal respiratory distress, which was unexpected as previous trials focusing on gestational diabetes diagnosed at later stages of pregnancy did not show a decrease in respiratory distress. The incidence of stillbirth or neonatal death was similar between the two trial groups and relatively low overall.
Previous trials on gestational diabetes treatment have primarily focused on cases diagnosed at 24 to 28 weeks gestation. However, this trial aimed to assess the effects of early initiation of treatment. The study used a composite outcome that included clinically important conditions but excluded outcomes dependent on local practices, such as cesarean delivery and neonatal ICU admission. The observed reduction in adverse outcomes can be attributed to early treatment initiation since all women in the control group received treatment after being diagnosed at 24 to 28 weeks gestation.
Exploratory subgroup analyses suggested a possible benefit of early treatment for women with higher glycemic levels and those diagnosed with hyperglycemia before 14 weeks gestation. However, it also indicated a potential increased risk of small-for-gestational-age infants among mothers with lower glycemic values. These analyses are considered hypothesis-generating and require further investigation.
The trial results raised questions about the criteria established for diagnosing gestational diabetes during early pregnancy, particularly considering that a significant portion of women diagnosed early did not have gestational diabetes on repeat testing at 24 to 28 weeks’ gestation. Further confirmatory trials and long-term follow-up studies of the offspring are needed to validate the findings.
The study’s limitations included the nonstandardized approach to treatment and the use of treatment targets established for the third trimester, which may not be optimized for early pregnancy. The trial focused on women with risk factors for hyperglycemia, so the results may not be applicable to the general population of pregnant women. The study