Re: “Timing of Gestational Diabetes Diagnosis by Maternal Obesity Status: Impact on Gestational Weight Gain in a Diverse Population” by Hillier et al.

We were interested by the recent article from Hillier et al., who reported that women who had an early diagnosis of gestational diabetes mellitus (GDM) gained 2.4 kg less during pregnancy than women with usual diagnosis at 24–28 weeks of gestation. ¹ As underlined by the authors, the early (first 18 weeks) gestational weight gain (GWG) seems critical to determine birth weight. ² The dietary counseling after the early diagnosis of GDM may, therefore, help to reduce the high risk of delivering a large for gestational age (LGA) newborn in early GDM. ³

In 322 women with GDM, we registered the early GWG at the first diabetological visit. Seventy-seven (23.9%) women had an early diagnosis of GDM, similar to 24.2% in Hillier's study. Their early GWG were lower: +0.15 ± 0.19 kg/gestational week versus +0.28 ± 0.16 for women with usual GDM (p < 0.001): only 31.6% of early GDM had a GWG higher than expected according to the objective of the Institute of Medicine versus 52.0% for usual GDM (p < 0.005 by chi square). The rates of LGA newborns from women with early GDM tended to be lower 5.3% versus 9.9% from women usual GDM (p = 0.09 by chi square). By multivariate binary logistic regression analysis, LGA newborns were related to a higher than expected early GWG (odds ratio [OR]: 4.20; confidence interval [95% CI]: 1.62–10.85), and not to early GDM (OR: 0.68; 95% CI: 0.22–2.10). Reducing the early GWG, as allowed by an early diagnosis and medical treatment, may, therefore, help to reduce the risk of LGA among women with GDM. The early screening of GDM was performed only in 26% of Hillier's population, and 30% of our patients, which shows that there is a large window of intervention to improve the outcome of pregnancy by early GDM screening.

Whether the generalization of early screening and treatment for GDM would reduce GWG and macrosomia is, however, not certain. The early screening was performed at 10 weeks of gestation in Hillier's study, and as shown by their figure 2, the first trimester weight gains were already lower for women with early diagnosis, which can hardly be attributed to a treatment beginning at the end of this first trimester: some motivated women may have both obtained an early screening and a lower early GWG. The benefit of the early screening will only concern the ∼10% women with positive screening, whereas in Hillier's report the most frequently excessive GWG were in women without GDM: 65% for obese and 46.7% for nonobese women. These women will not have a specific dietary counseling if it occurs only after an early diagnosis of GDM. Because excessive GWG is a significant predictor of GDM, ⁴ and a stronger predictor of adverse pregnancy outcome, ⁵ the most efficient mean to reduce their frequency may be its use as an argument for selective GDM screening, and treatment, rather than the universalization of early GDM screening and dietary advices, which will have to be tested through a randomized controlled trial.