Raised maternal body mass index and caesarean section

Abstract

Introduction Maternal obesity (defined as a body mass index (BMI) ≥30kg/m2) and overweight (defined as BMI 25-29.9kg/m2) have adverse implications for both the mother and the baby, including an increased risk of caesarean section. The prevalence of caesarean section among the UK obstetric population has been increasing in recent years. Evidence suggests that caesarean section in obese women may carry a higher risk of postoperative complications, such as haemorrhage, wound infection and delayed healing. These complications may result in a longer length of stay in hospital after caesarean delivery. To date, UK evidence on the association between maternal BMI and caesarean section has been limited. Aim The overall aim of my PhD was to investigate the association between maternal BMI and caesarean section within the North East of England. Methods and Results My PhD consists of three phases: Phase one: a review of the available published literature that investigated the association between maternal BMI and caesarean section rate. The review found that most studies been carried out in the US with only six from the UK. The review highlighted the need for further research in the UK. Phase two: an investigation of the association between maternal early pregnancy BMI and caesarean section using an existing dataset of 42,362 deliveries in five hospitals in the North East of England. The objectives of this phase were; to identify the caesarean section rate among five hospitals in the North East of England; to describe the caesarean section rate by booking BMI; and to examine the independent impact of BMI on caesarean section, adjusting for potentially confounding variables including maternal age, gestational age, birth weight, ethnicity and socio-economic status in overweight and obese pregnant women compared to pregnant women with recommended BMI. In phase two, the overall caesarean section rate was 20.6%; 28.4% of obese and 21.9% of overweight women delivered by caesarean section, compared to 17.8% of women with recommended BMI. After adjusting for available confounding factors, the adjusted odds ratio (aOR) for caesarean section among obese women was 1.81 (95%CI: 1.67-1.97; p<0.0005) and 1.29 (95%CI: 1.20-1.39; p<0.0005) among overweight women compared to women with recommended BMI. Thus, there was an almost two-fold increased risk of delivery by caesarean section among women who were obese at the start of pregnancy and an increased risk for women who were overweight. Phase three: a case note review of 205 women with a singleton pregnancy in 2008, aged ≥16 years and delivered by caesarean section in a district general hospital in the North East of England. The study hypothesis was that overweight and obese pregnant women have more post-caesarean section complications than pregnant women with recommended BMI, resulting in a longer length of stay in hospital. The results of this study showed that from 205 cases (28% of all caesarean section deliveries in 2008), 86 (42.0%) were to women with recommended BMI, 54 (26.3%) to overweight and 65 (31.7%) to obese women. The median length of maternal stay in hospital was three days, with an inter quartile range (IQR) of 2-3. Twelve (18.5%) obese women stayed in hospital after caesarean section for four days compared to five (9.3%) overweight and eight (9.4%) women with recommended BMI, (p=0.44) but this was not significant. There were no significant differences in postoperative complications or length of stay in hospital between overweight and obese pregnant women compared to women with recommended BMI. Conclusion Overall, my study confirms that obese and overweight women in the North East of England are at increased risk of caesarean section. Among women delivered by caesarean section, however, there was no association between maternal BMI and post-operative complications or length of stay in hospital.