Objective
To quantify late‐pregnancy weight gain in women with and without gestational diabetes mellitus (GDM) and to determine factors associated with gestational weight gain.

Study design
A prospective clinical audit of 212 women (115 GDM and 97 non‐GDM) who were weighed at each antenatal visit from 24–32 weeks gestation until delivery. Women received routine antenatal clinical care. For women with GDM, this included a 2‐h lifestyle counselling session, capillary blood glucose testing and frequent clinical review.

Results
Women with GDM gained less weight than nondiabetic women (GDM: 1.18 kg (1.6%) [range, 3.8–7.1 kg]; non‐GDM: 4.0 kg (4.8%) [range, 0.7–18.5 kg]; P < 0.0001). Weight gain was influenced by body mass index and country of birth. Women with GDM showed reduced weight gain at weeks 1–4 postrecruitment, relative to weeks 4–8 (0.04 kg/week vs 0.45 kg/week; P < 0.0001). Nondiabetic women gained weight at a constant rate. GDM status was the only independent predictor of postrecruitment weight gain. Conclusions Application of a model of care for GDM (lifestyle advice and regular clinical review, in addition to home glucose monitoring) may reduce weight gain in women with GDM. The potential for applying a modified version of this model to all women in pregnancy warrants further study.