Gestational diabetes mellitus treatment reduces obesity-induced adverse pregnancy and neonatal outcomes: the St. Carlos gestational study.

Background: Obesity and gestational diabetes mellitus (GDM) increase the morbidity of the mother and newborn, which could increase further should they coexist. We aimed to determine the risk of adverse pregnancy and neonatal outcomes associated with excess weight (EW), and within this group identify potential differences between those with and without GDM.

Methods: We carried out a post-hoc analysis of the St. Carlos Gestational Study which included 3312 pregnant women, arranged in 3 groups: normal-weight women (NWw) (2398/72.4%), overweight women (OWw) (649/19.6%) and obese women (OBw) (265/8%). OWw and OBw were grouped as EW women (EWw). We analyzed variables related to adverse pregnancy and neonatal outcomes.

Results: The relative risk (95% CI) for GDM was 1.82 (1.47 to 2.25; p<0.0001) for OWw, and 3.26 (2.45 to 4.35; p<0.0001) in OBw. Univariate analysis showed associations of EW to higher rates of prematurity, birth weight >90th centile, newborns admitted to neonatal intensive care unit (NICU), instrumental delivery and cesarean delivery (all p<0.005). Multivariate analysis, adjusted for parity and ethnicity, showed that EW increased the risk of prematurity, admission to NICU, cesarean and instrumental delivery, especially in EWw without GDM. NWw with GDM had a significantly lower risk of admission to NICU and cesarean delivery, compared with NWw without GDM.

Conclusions: EW is detrimental for pregnancy and neonatal outcomes, and treatment of GDM contributes to lowering the risk in EWw and NWw. Applying the same lifestyle changes to all pregnant women, independent of their weight or GDM condition, could improve these outcomes.