Are the Institute of Medicine weight gain targets applicable in women with gestational diabetes mellitus?

Aims/hypothesis: Our aim was to study the relationship between excessive gestational weight gain (GWG) according to Institute of Medicine (IOM) targets and perinatal outcomes, and examine whether modifying targets may improve outcomes in women with gestational diabetes mellitus (GDM). Methods: This was a retrospective cohort study of all GDM pregnancies from 1992 to 2013. ORs were calculated for associations between excessive GWG (EGWG) using IOM targets and adverse pregnancy outcomes. ORs were then adjusted for maternal age, gestational age at diagnosis, prepregnancy BMI, gravidity, parity, ethnicity, antenatal fasting blood glucose level (BGL), 2 h BGL and HbA1c. BMI was categorised into underweight (<18.5 kg/m2), healthy weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2) and obese (≥30 kg/m2). Large for gestational age (LGA) was defined as birthweight above the 90th percentile, small for gestational age (SGA) was birthweight below the 10th percentile, macrosomia was birthweight >4000 g, and preterm delivery was delivery prior to 37 weeks’ gestation. Modified GWG targets were derived by: (1) subtracting 2 kg from the upper IOM target only; (2) subtracting 2 kg from both upper and lower targets; (3) using the interquartile range of maternal GWG of women with infants who were appropriate for gestational age per BMI category; and (4) restricting GWG to 0–4 kg in women with BMI ≥35 kg/m2. Results: Among 3095 GDM pregnancies, only 31.7% had GWG within IOM guidelines. Adjusted ORs for women who exceeded GWG were Caesarean section (1.5; 95% CI 1.2, 1.9), LGA (1.8; 95% CI 1.4, 2.4) and macrosomia (2.3; 95% CI 1.6, 3.3); there was a lower risk of SGA (adjusted OR 0.5; 95% CI 0.3, 0.7). Conclusions/interpretation: EGWG according to IOM targets was associated with Caesarean section, LGA and macrosomia. Modification of IOM criteria, including more restrictive targets, did not improve perinatal outcomes.