Effect of Body Mass Index on pregnancy outcomes in nulliparous women delivering singleton babies

• Main Authors: Liston William A, Campbell Doris M, Bhattacharya Sohinee, Bhattacharya Siladitya
• Format: Article
• Language: English
• Published: BMC 2007-07-01
• Series: BMC Public Health
• Online Access: http://www.biomedcentral.com/1471-2458/7/168

<p>Abstract</p> <p>Background</p> <p>The increasing prevalence of obesity in young women is a major public health concern. These trends have a major impact on pregnancy outcomes in these women, which have been documented by several researchers. In a population based cohort study, using routinely collected data, this paper examines the effect of increasing Body Mass Index (BMI) on pregnancy outcomes in nulliparous women delivering singleton babies.</p> <p>Methods</p> <p>This was a retrospective cohort study, based on all nulliparous women delivering singleton babies in Aberdeen between 1976 and 2005. Women were categorized into five groups – underweight (BMI < 20 Kg/m²), normal (BMI 20 – 24.9 Kg/m²) overweight (BMI 25 – 29.9 Kg/m²), obese (BMI 30 – 34.9 Kg/m²) and morbidly obese (BMI > 35 Kg/m²). Obstetric and perinatal outcomes were compared by univariate and multivariate analyses.</p> <p>Results</p> <p>In comparison with women of BMI 20 – 24.9, morbidly obese women faced the highest risk of pre-eclampsia {OR 7.2 (95% CI 4.7, 11.2)} and underweight women the lowest {OR 0.6 (95% CI 0.5, 0.7)}. Induced labour was highest in the morbidly obese {OR 1.8 (95% CI 1.3, 2.5)} and lowest in underweight women {OR 0.8 (95% CI 0.8, 0.9)}. Emergency Caesarean section rates were highest in the morbidly obese {OR 2.8 (95% CI 2.0, 3.9)}, and comparable in women with normal and low BMI. Obese women were more likely to have postpartum haemorrhage {OR 1.5 (95% CI 1.3, 1.7)} and preterm delivery (< 33 weeks) {OR 2.0 (95% CI 1.3, 2.9)}. Birthweights less than 2,500 g were more common in underweight women {OR 1.7 (95% OR 1.2, 2.0)}. The highest risk of birth weights > 4,000 g was in the morbidly obese {OR 2.1 (95% CI 1.3, 3.2)} and the lowest in underweight women {OR 0.5 (95% CI 0.4, 0.6)}.</p> <p>Conclusion</p> <p>Increasing BMI is associated with increased incidence of pre-eclampsia, gestational hypertension, macrosomia, induction of labour and caesarean delivery; while underweight women had better pregnancy outcomes than women with normal BMI.</p>