BACKGROUND: Optimal gestational weight change (GWC) is little known among pregnant women with gestational diabetes mellitus (GDM).
OBJECTIVE: This study aimed to explore the optimal GWC ranges for women with GDM and validate these ranges compared with the Institute of Medicine (IOM) guidelines.
METHODS: A population-based cohort study using natality data from the National Center for Health Statistics in the United States included 1,338,460 mother-infant pairs with GDM from 2014 to 2020. Poisson regression models were performed to identify GWC ranges (GDM targets) associated with acceptable risks (<10% increase) for a severity-weighted composite outcome including preterm birth (PTB) <37 wk, large for gestational age (LGA, birthweight >90th percentile) and small for gestational age (SGA, birthweight <10th percentile). These targets were validated in individual outcomes including PTB, LGA, SGA, hypertensive disorders of pregnancy, neonatal intensive care unit admission, and neonatal respiratory morbidity, and compared with the IOM guidelines using logistic regression models with population-attributable fractions (PAFs) calculated.
RESULTS: The severity-weighted composite outcome had a U-shaped or a J-shaped relationship with GWC across body mass index categories. The GDM targets were 14.1 to 20.3 kg, 9.0 to 17.0 kg, 4.8 to 13.8 kg, -0.8 to 10.8 kg, -2.4 to 8.2 kg, and -8.3 to 6.0 kg for underweight, normal weight, overweight, class 1 obesity, class 2 obesity, and class 3 obesity, respectively. GWC outside the GDM or the IOM targets was associated with increased adverse perinatal outcomes in validation analyses. PAFs indicated that the IOM guidelines reduced a similar or higher proportion of adverse perinatal outcomes compared with the GDM targets for women with GDM, except for those with class 2 and 3 obesity.
CONCLUSIONS: The IOM guidelines are generally applicable for women with GDM, except for women with moderate and severe obesity. The optimal GWC ranges for women with GDM and moderate to severe obesity may be lower than the IOM guidelines.

Pregnancy is an excellent opportunity to provide medical interventions to women. It is also a stress test used to predict health. Numerous studies have demonstrated that the pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) are critical factors for pregnancy complications such as hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), large or small gestational age infants, and spontaneous preterm birth (sPTB). These complications are associated with an increased risk of cardiovascular disease (CVD), which is a leading cause of mortality in women. In addition, complications adversely affect the short- and long-term prognoses of children. Optimal GWG to reduce complications is recommended based on pre-pregnancy BMI; however, racial differences should also be noted. The values in the Japanese guidelines are lower than those in the American Institute of Medicine guidelines. The Asian BMI thresholds for CVD risk are also lower than those in Europe. Therefore, weight management should be based on racial/genetic background. Interpregnancy weight gain or loss has also been reported to be associated with the risk of pregnancy complications; however, few studies have been conducted in Asian populations. Our previous reports suggested that avoiding an excess of 0.6 kg/m2/year of annual BMI gain may reduce the risk of HDP or GDM, and insufficient gain of < 0.25 kg/m2/year may increase sPTB recurrence. Annual BMI is useful for practical weight control during interpregnancy. Based on these findings, effective approaches should be established to improve the health of women and their offspring.