The effect of a prenatal lifestyle intervention on glucose metabolism: results of the Norwegian Fit for Delivery randomized controlled trial.

Background: The effectiveness of prenatal lifestyle intervention to prevent gestational diabetes and improve maternal glucose metabolism remains to be established. The Norwegian Fit for Delivery (NFFD) randomized, controlled trial studied the effect of a combined lifestyle intervention provided to a general population, and found significantly lower gestational weight gain among intervention participants but no improvement in obstetrical outcomes or the proportion of large infants. The aim of the present study is to examine the effect of the NFFD intervention on glucose metabolism, including an assessment of the subgroups of normal-weight and overweight/obese participants.

Methods: Healthy, non-diabetic women expecting their first child, with pre-pregnancy body mass index (BMI) ≥19 kg/m, age ≥ 18 years and a singleton pregnancy of ≤20 gestational-weeks were enrolled from healthcare clinics in southern Norway. Gestational weight gain was the primary endpoint. Participants (n = 606) were individually randomized to intervention (two dietary consultations and access to twice-weekly exercise groups) or control group (routine prenatal care). The effect of intervention on glucose metabolism was a secondary endpoint, measuring glucose (fasting and 2-h following 75-g glucose load), insulin, homeostatic assessment of insulin resistance (HOMA-IR) and leptin levels at gestational-week 30.

Results: Blood samples from 557 (91.9%) women were analyzed. For the total group, intervention resulted in reduced insulin (adj. Mean diff -0.91 mU/l, p = 0.045) and leptin levels (adj. Mean diff -207 pmol/l, p = 0.021) compared to routine care, while glucose levels were unchanged. However, the effect of intervention on both fasting and 2-h glucose was modified by pre-pregnancy BMI (interaction p = 0.030 and p = 0.039, respectively). For overweight/obese women (n = 158), intervention was associated with increased risk of at least one glucose measurement exceeding International Association of Pregnancy and Diabetes Study Group thresholds (33.7% vs. 13.9%, adj. OR 3.89, p = 0.004).

Conclusions: The Norwegian Fit for Delivery intervention lowered neither glucose levels nor GDM incidence, despite reductions in insulin and leptin. Prenatal combined lifestyle interventions designed for a general population may be unsuited to reduce GDM risk, particularly among overweight/obese women, who may require earlier and more targeted interventions.

Trial Registration: ClinicalTrials.gov ID NCT01001689 , registered July 2, 2009, confirmed completed October 26, 2009 (retrospectively registered).