Change of maternal weight gain trajectory following lifestyle interventions for gestational diabetes and its impact on abnormal infant birthweight: an observational study based on longitudinal weight measurements.

BACKGROUND: Restricted gestational weight gain (GWG) following lifestyle interventions for gestational diabetes mellitus (GDM) has been observed in clinical trials but not been explicitly confirmed in real-world clinical settings. Furthermore, how such a restricted GWG affects adverse birthweight outcomes, i.e. infants born large/small for gestational age (LGA/SGA), remains unclear. METHOD: In this retrospective study, based on longitudinal weight measurements from 33,515 Chinese women, including 5,932 with GDM diagnosed by 75-g oral glucose tolerance test (OGTT), we compared the adjusted GWG trajectories of women with and without GDM. We estimated weekly GWG before and after OGTT (WGWGpre−OGTT and WGWGpost−OGTT) and calculated ΔWGWG as WGWGpre−OGTT minus WGWGpost−OGTT. We then estimated the adjusted relative risks (aRR) of LGA and SGA for restricted vs. unrestricted WGWGpost−OGTT (ΔWGWG > 0 vs. ≤0 kg) among women with GDM. The analyses were stratified by prepregnancy body mass index (pBMI). RESULTS: There was a marked decrease between the mean estimated WGWGpre−OGTT (0.50 kg) and WGWGpost−OGTT (0.36 kg) in women with GDM, in contrast to a negligible decrease from 0.52 to 0.51 kg in women without GDM. Using 14–19 gestational weeks as the baseline, the cumulative GWG since the baseline became statistically significantly less in women with than without GDM after the initiation of lifestyle interventions, regardless of their pBMI category. Women with an underweight, normal-weight, and overweight/obese pBMI gained by an adjusted median of 1.84 [95% confidence interval (CI): 1.50, 2.17], 2.53 (2.38, 2.68), and 2.99 kg (2.63, 3.35) less, respectively, than their non-GDM counterparts by the end of gestation (38–39 weeks). Among women with GDM, a restricted WGWGpost−OGTT showed no association with either LGA or SGA for underweight pBMI, a null association with SGA but a statistically significant association with a reduced risk of LGA for normal-weight pBMI [aRR (95% CI): 1.02 (0.82, 1.28) and 0.62 (0.49, 0.79), respectively], and opposite although non-significant associations for overweight/obese pBMI [ aRR (95% CI): 1.22 (0.66, 2.28) for SGA and 0.74 (0.52, 1.06) for LGA]. CONCLUSIONS: Lifestyle interventions for GDM are likely to cause a substantially restricted GWG, which however might only have a fully beneficial effect on infant birthweight for women with a normal-weight pBMI.