Currently there are no UK guidelines regarding safe weight gain in pregnancy. Obesity (BMI ⩾ 30 kg/m²) and excessive weight gain in pregnancy are associated with serious health risks to both mother and baby including gestational diabetes, macrosomia, pre-eclampsia, caesarean section and post operative complicationsReference Galtier-Dereure, Boegner and Bringer ¹ . In the absence of UK guidance, USA recommendations are often referred to which suggest that women with a pre-pregnancy BMI >29·9 kg/m² should limit gestational weight gain (GWG) to 5–9 kg ² . The aim of this study was to explore patterns of GWG in obese pregnancies in comparison to USA IOM recommendations. Women with BMI >29·9 kg/m² were recruited from antenatal clinic at booking-in appointments and agreed to being weighed at each trimester of pregnancy. Weight change was calculated and then compared with categorised pregnancy weight gain (<0 kg, 0–5 kg, 5–9 kg and >9 kg). Between June 2009 and June 2010, 824 women consented to participate and weight data were collected for 756 women (table 1).

Table 1: Gestational weight gain compared to USA IOM BMI categories

Missing weight data made statistical analysis difficult but results suggest that increasing booking-in BMI was associated with deceased risk of excessive weight gain (>9 kg). In a model to assess predictors of GWG a higher booking BMI was negatively associated with GWG (β −0·25, 95 % CI −0·32 to −0·19, p < 0·001). Due to finite resources, only women with a booking-in BMI ⩾ 40 kg/m² are currently offered specialist obesity care at the study hospital, despite NICE ³ recommending specialist care for BMI ⩾ 30 kg/m². These results suggest that pregnant women with BMI 30–39·9 kg/m² may be at greater risk of excessive GWG and yet are only offered routine antenatal care. A review of ante natal care provision for overweight pregnancies is urgently needed.