Prepregnancy BMI, Gestational Weight Gain, and Cesarean Birth
Prepregnancy BMI, Gestational Weight Gain, and Cesarean Birth
The prevalence of overweight and obesity, defined as a body mass index (BMI) of 25–29.9 kg/m and ≥ 30 kg/m respectively, has been increasing globally. In Canada, based on measured height and weight, the prevalence of obesity among adult women rose from 16% in 1978 to 23% in 2004. Correspondingly, rates of obesity are also increasing among pregnant women. Overweight and obese women are known to be at increased risk of serious pregnancy complications including caesarean birth. These caesarean births in turn increase women's risk of infection, haemorrhage, damage to the intestines or bladder, and negatively affect early parenting outcomes. Caesarean births also increase the risk of long-term complications such as abnormal placentation during subsequent pregnancies and place excess strain on the healthcare system. Canadian caesarean birth rates rose from 18% in 1995–1996 to 28% in 2010–2011.
The concomitant increase in overweight and obesity and caesarean births make it important to study to what degree maternal weight is contributing to these births. During pregnancy, maternal weight is a product of both prepregnancy body mass index (BMI), hereafter referred to as BMI, and gestational weight gain (GWG). Estimating the magnitude of the independent as well as joint association between these determinants and caesarean births is essential for designing interventions that promote healthy pregnancy outcomes. However, to date, few studies have quantified the proportion of caesarean births at the population level that are associated with above normal BMI and no studies have quantified the proportion associated with excess GWG. Data from the Canadian Maternity Experiences Survey provided a unique opportunity to address this issue for Canada.
Background
The prevalence of overweight and obesity, defined as a body mass index (BMI) of 25–29.9 kg/m and ≥ 30 kg/m respectively, has been increasing globally. In Canada, based on measured height and weight, the prevalence of obesity among adult women rose from 16% in 1978 to 23% in 2004. Correspondingly, rates of obesity are also increasing among pregnant women. Overweight and obese women are known to be at increased risk of serious pregnancy complications including caesarean birth. These caesarean births in turn increase women's risk of infection, haemorrhage, damage to the intestines or bladder, and negatively affect early parenting outcomes. Caesarean births also increase the risk of long-term complications such as abnormal placentation during subsequent pregnancies and place excess strain on the healthcare system. Canadian caesarean birth rates rose from 18% in 1995–1996 to 28% in 2010–2011.
The concomitant increase in overweight and obesity and caesarean births make it important to study to what degree maternal weight is contributing to these births. During pregnancy, maternal weight is a product of both prepregnancy body mass index (BMI), hereafter referred to as BMI, and gestational weight gain (GWG). Estimating the magnitude of the independent as well as joint association between these determinants and caesarean births is essential for designing interventions that promote healthy pregnancy outcomes. However, to date, few studies have quantified the proportion of caesarean births at the population level that are associated with above normal BMI and no studies have quantified the proportion associated with excess GWG. Data from the Canadian Maternity Experiences Survey provided a unique opportunity to address this issue for Canada.
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