Testing high risk women for gestational diabetes before 20 weeks of pregnancy may reduce adverse maternal and neonatal outcomes, according to results from the multicenter Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) trial published in the New England Journal of Medicine.¹

This randomized, controlled trial was conducted by researchers from Australia, Vienna, Sweden and India with the objective to compare the outcomes of immediate treatment for gestational diabetes starting before 20 weeks of gestation based on OGTT performed at 15.6 gestational weeks (mean) vs deferred or no treatment according to results of a repeat oral glucose-tolerance test [OGTT] at 24 to 28 weeks’ gestation, which acted as the control group. A total of 802 women with at least one risk factor for hyperglycemia and who were diagnosed with gestational diabetes as per the WHO criteria were selected for the study; 406 (50.6%) women with fasting glucose of at least 91.8 mg/dl, 1-hour glucose of at least 180. mg/dl, or 2-hour glucose of at least 153 mg/dl were randomized to the immediate-treatment group and 396 (49.4%) were assigned to the control group.

A composite of adverse neonatal outcomes (birth before <37 weeks’ gestation, birth trauma, birth weight of ≥4500 g, respiratory distress, phototherapy, stillbirth or neonatal death, or shoulder dystocia), pregnancy-related hypertension (gestational hypertension, preeclampsia or eclampsia) and neonatal lean body mass were determined as the primary outcomes of the study.

After excluding women with early pregnancy loss, 793 women (98.9%) were included in the final analysis. Sixty-seven percent of women in the control group were diagnosed with gestational diabetes on repeat OGTT.

The adverse neonatal outcomes occurred in 24.9% of the 378 women in the immediate-treatment group compared with 30.5% of the 370 women in the control group with an adjusted risk difference of 5.6 percentage points and a number needed to treat (NNT) of 18. The effect was most robust for neonatal respiratory distress; 9.8% vs 17.0% of infants in the immediate- and deferred-treatment groups, respectively. Nearly 11% of women in the immediate-treatment group developed pregnancy-related hypertension compared to ~10% in the control group with an adjusted risk difference of 0.7 percentage points. The mean neonatal lean body in the immediate-treatment group mass was 2.86 g and in the control group it was 2.91 g. The adjusted mean difference was −0.04 g.

On the basis of the 95% confidence interval around the estimated difference, the results were compatible with anywhere from a 1.2 to a 10.1 percentage point reduction in the risk of an adverse neonatal outcome event. No significant difference was shown with respect to the two other prespecified primary outcomes (pregnancy-related hypertension and neonatal lean body mass). The major contributor to the between-group difference with respect to the first primary outcome was neonatal respiratory distress.

This study shows that fewer adverse neonatal events occurred in the immediate treatment group compared to the deferred treatment group, even though this effect was modest. It was principally due to the lower incidence of neonatal respiratory distress following immediate treatment. However, the difference between the two groups relating to pregnancy-related hypertension and neonatal lean body mass was non-significant. According to the authors, their findings suggest that women with higher glycemic levels on OGTT were more likely to benefit from the early treatment. They also caution that early treatment in women with glycemia in the lower range may be associated with increased risk of small-for-gestational-age infants.

Reference

1. Simmons D, et al; TOBOGM Research Group. Treatment of gestational diabetes mellitus diagnosed early in pregnancy. N Engl J Med. May 5, 2023. DOI: 10.1056/NEJMoa2214956.