OBJECTIVESince January 2008, obese women with type 2 diabetes were advised to gain 0-5 kg during pregnancy. The aim with this study was to evaluate fetal growth and perinatal morbidity in relation to gestational weight gain in these women.RESEARCH DESIGN AND METHODSA retrospective cohort comprised the records of 58 singleton pregnancies in obese women (BMI ≥30 kg/m(2)) with type 2 diabetes giving birth between 2008 and 2011. Birth weight was evaluated by SD z score to adjust for gestational age and sex.RESULTSSeventeen women (29%) gained ≤5 kg, and the remaining 41 gained >5 kg. The median (range) gestational weight gains were 3.7 kg (-4.7 to 5 kg) and 12.1 kg (5.5-25.5 kg), respectively. Prepregnancy BMI was 33.5 kg/m(2) (30-53 kg/m(2)) vs. 36.8 kg/m(2) (30-48 kg/m(2)), P = 0.037, and median HbA(1c) was 6.7% at first visit in both groups and decreased to 5.7 and 6.0%, P = 0.620, in late pregnancy, respectively. Gestational weight gain ≤5 kg was associated with lower birth weight z score (P = 0.008), lower rates of large-for-gestational-age (LGA) infants (12 vs. 39%, P = 0.041), delivery closer to term (268 vs. 262 days, P = 0.039), and less perinatal morbidity (35 vs. 71%, P = 0.024) compared with pregnancies with maternal weight gain >5 kg.CONCLUSIONIn this pilot study in obese women with type 2 diabetes, maternal gestational weight gain ≤5 kg was associated with a more proportionate birth weight and less perinatal morbidity.