Increasing UK obesity includes expectant women1; the Confidential Enquiry into Maternal and Child health (2000-2) showed that 35% of all women who died were obese, compared with 23% of the general population. Risks for babies of obese women include stillbirth, macrosomia, prematurity and neonatal death2. We wished to determine the change in incidence of obesity in pregnant women, associated maternal disorders and the obstetric sequelae for women in our clinic. The electronic database of York Teaching Hospital antenatal department was interrogated to establish the number of obese women ( O, body mass index (BMI) >30 Kg/m2 ) and super obese ( SO, BMI >50 Kg/m2) women who booked in to the clinic and who delivered. The incidence of O and SO rose between 2001 and 2011 ( Fig.1 ). Using the database, we identified all 6 SO who presented in 2011 and matched them against 6 non obese N (BMI <30) women who delivered the same day (Total annual deliveries 3391, 3826 women booked in 2011). The proportion of asthma (67% vs 19%), diabetes (50% vs 0%), and depression (50% vs 17%) was higher in SO than N (BMI <30). A further 30 O and 20 N women were identified and evaluated; 16 O and 0 N had impaired glucose tolerance. Mean(range) resting oxygen saturation supine awake at rest was 99(98-100)% in N and 98(97-100)% in SO & O (p=0.016, unpaired t-test). Snoring was seen in 67% SO & O and 40% N ( p=0.07, χ2). No difference was seen in the mean Epworth sleepiness scores in these patients (6.2 in O, 6.6 in N) or mean(range) heart rate (84.7(72-106) bpm in O and SO, 81.5(70-99) bpm in N), indicating that these measures are insensitive in distinguishing these patients. Both maternal systolic and diastolic blood pressure increased with BMI at booking and at 36 week gestation. Mean(range) weight gain during pregnancy was 6.3 (-5 – 20)kg in O and SO and 10(1-16)kg in N, indicating some effectiveness of antenatal care. Only 67 % SO delivered babies in an acceptable weight range (birth weight 2.7-4Kg) vs. all N. 37.5% O and SO had miscarriages vs 8.3% N (p=0.066, χ2). In 2014, a further 7 O ( 4 caesarean births) and 7 matched N (2 caesarean)were evaluated. Obesity has a significant and increasing burden on the respiratory and metabolic health of mothers and adversely affected obstetric outcomes.