First and second pregnancy outcomes in women with class III obesity: an observational cohort study

Introduction Class III obesity (BMI≥40kg/m2) during pregnancy predisposes mother and offspring to a range of adverse pregnancy complications and outcomes. Risk profiles vary between pregnancies and are affected by interpregnancy weight gain. We evaluated the risk of adverse outcomes in women with BMI≥40kg/m2 in first and second pregnancies, and the impact of interpregnancy weight change on this risk. Materials and methods Data were extracted for all women with BMI≥40kg/m2 at first antenatal visit, who completed antenatal and delivery care for first and second pregnancies in NHS Lothian between 1/1/2009–31/12/2018. Multiple pregnancies and recipients of bariatric surgery were excluded. Results 442 pregnancies among 221 women were included. In first pregnancy, median (interquartile range) weight was 117kg (108.5-126.7), age 28 years (24-31) and BMI 42kg/m2 (41.0-44.5), 14.4% had gestational diabetes (GDM), 11.3% had pregnancy-induced hypertension and 44.6% had a post-partum haemorrhage (PPH). 20.8% of babies were large for gestational age (LGA, ≥97% centile at birth). In second pregnancy, women were heavier with a median weight of 119.9kg (109.0-130.0, p=0.00) with 19.9% gaining over 10kg. Women were more likely to develop GDM (21.6%, p=0.02). Babies were heavier with 40% of babies LGA(p<0.0001). Interpregnancy weight change had no significant impact on GDM, pregnancy induced hypertension, PPH, perinatal mortality or LGA. Conclusions In a population of women with BMI≥40kg/m2, pregnancy complications are common and risk is higher in second pregnancy. The interpregnancy period is a critical time to engage women in health improvement and weight loss strategies to maximise outcomes for mother and offspring.