Pre-pregnancy body mass index and length of gestation at term

Abstract

ObjectiveTo examine the relationship between pre-pregnancy body mass index (BMI) and length of gestation at term.Study designThis was a retrospective study of 10,878 parturients. We excluded preterm births, multiple gestations, and elective cesareans without labor. We performed univariate and multivariate analyses of the associations between pre-pregnancy BMI and length of gestation (>40 weeks, >41 weeks, and >42 weeks).ResultsOverweight women were more likely to deliver at >40 weeks, >41 weeks, and >42 weeks than women who were underweight or normal weight (Table 1). In multivariate analyses, higher pre-pregnancy BMI (as a continuous variable) was associated with longer length of gestation at term. Obese women had a 30% higher adjusted odds of reaching 42 weeks gestation compared to women of normal pre-pregnancy BMI (adjusted odds ratio 1.30, 95% CI 1.08-1.57) (Table 2).ConclusionHigher BMI is associated with longer gestation at term. Despite the fact that higher BMI is associated with gestational diabetes and hypertension, conditions that frequently require delivery prior to 40 weeks gestation, overweight women were more likely to go past their estimated due date. Achieving a healthy BMI prior to conception may reduce the risk of postterm pregnancy and its associated complications.Table 1Pre-pregnancy BMI and length of gestation at termLow BMINormal BMIHigh BMIObese BMIp-valueGA >40 weeks50.9%52.5%53.0%57.0%GA >41 weeks19.8%23.1%24.75%29.0%GA >42 weeks3.4%4.7%6.1%5.7% Open table in a new tab Table 2Multivariate analysis of pre-pregnancy BMI and length of term gestationLow BMINormal BMIHigh BMIObese BMIGA >40 weeks0.95 (0.89-1.01)Reference1.08 (0.99-1.18)1.31 (1.19-1.46)GA >41 weeks0.83 (0.77-0.89)Reference1.19 (1.08-1.32)1.39 (1.24-1.57)GA >42 weeks0.77 (0.68-0.87)Reference1.24 (1.06-1.46)1.30 (1.08-1.57) Open table in a new tab ObjectiveTo examine the relationship between pre-pregnancy body mass index (BMI) and length of gestation at term. To examine the relationship between pre-pregnancy body mass index (BMI) and length of gestation at term. Study designThis was a retrospective study of 10,878 parturients. We excluded preterm births, multiple gestations, and elective cesareans without labor. We performed univariate and multivariate analyses of the associations between pre-pregnancy BMI and length of gestation (>40 weeks, >41 weeks, and >42 weeks). This was a retrospective study of 10,878 parturients. We excluded preterm births, multiple gestations, and elective cesareans without labor. We performed univariate and multivariate analyses of the associations between pre-pregnancy BMI and length of gestation (>40 weeks, >41 weeks, and >42 weeks). ResultsOverweight women were more likely to deliver at >40 weeks, >41 weeks, and >42 weeks than women who were underweight or normal weight (Table 1). In multivariate analyses, higher pre-pregnancy BMI (as a continuous variable) was associated with longer length of gestation at term. Obese women had a 30% higher adjusted odds of reaching 42 weeks gestation compared to women of normal pre-pregnancy BMI (adjusted odds ratio 1.30, 95% CI 1.08-1.57) (Table 2). Overweight women were more likely to deliver at >40 weeks, >41 weeks, and >42 weeks than women who were underweight or normal weight (Table 1). In multivariate analyses, higher pre-pregnancy BMI (as a continuous variable) was associated with longer length of gestation at term. Obese women had a 30% higher adjusted odds of reaching 42 weeks gestation compared to women of normal pre-pregnancy BMI (adjusted odds ratio 1.30, 95% CI 1.08-1.57) (Table 2). ConclusionHigher BMI is associated with longer gestation at term. Despite the fact that higher BMI is associated with gestational diabetes and hypertension, conditions that frequently require delivery prior to 40 weeks gestation, overweight women were more likely to go past their estimated due date. Achieving a healthy BMI prior to conception may reduce the risk of postterm pregnancy and its associated complications.Table 1Pre-pregnancy BMI and length of gestation at termLow BMINormal BMIHigh BMIObese BMIp-valueGA >40 weeks50.9%52.5%53.0%57.0%GA >41 weeks19.8%23.1%24.75%29.0%GA >42 weeks3.4%4.7%6.1%5.7% Open table in a new tab Table 2Multivariate analysis of pre-pregnancy BMI and length of term gestationLow BMINormal BMIHigh BMIObese BMIGA >40 weeks0.95 (0.89-1.01)Reference1.08 (0.99-1.18)1.31 (1.19-1.46)GA >41 weeks0.83 (0.77-0.89)Reference1.19 (1.08-1.32)1.39 (1.24-1.57)GA >42 weeks0.77 (0.68-0.87)Reference1.24 (1.06-1.46)1.30 (1.08-1.57) Open table in a new tab Higher BMI is associated with longer gestation at term. Despite the fact that higher BMI is associated with gestational diabetes and hypertension, conditions that frequently require delivery prior to 40 weeks gestation, overweight women were more likely to go past their estimated due date. Achieving a healthy BMI prior to conception may reduce the risk of postterm pregnancy and its associated complications.