Table 2.
Adjusted odds ratios and 95% confidence intervals calculated for prolonged pregnancy or preterm delivery according to maternal BMI category at pregnancy booking in comparison to a normal BMI of 20–24.9 kg/m2
| Maternal BMI group at pregnancy booking | ||||||
|---|---|---|---|---|---|---|
| Underweight (n = 2087) | Normal weight (n = 9530) | Overweight (n = 5294) | Obese (n = 2051) | Very obese (n = 707) | Morbidly obese (n = 303) | |
| Preterm(n = 907) | 1.33 (1.09–1.62)* | 1.00 | 0.81 (0.68–0.97)* | 0.92 (0.72–1.17) | 0.84 (0.56–1.28) | 1.25 (0.72—0.19) |
| Term(n = 14 229) | Ref | 1.00 | Ref | Ref | Ref | Ref |
| Prolonged(n = 4836) | 0.75 (0.66–0.85)* | 1.00 | 1.24 (1.14–1.34)* | 1.52 (1.37–1.70)* | 1.75 (1.48–2.07)* | 2.27 (1.78–2.89)* |
Values are adjusted odds ratio (AOR) with 95% CI in parentheses. Analyses controlled for the following variables: maternal age, maternal race, parity, hypertension (pregestational or gestational), diabetes mellitus (pregestational or gestational) and smoking status. Normal weight and term pregnancy were used as the reference categories.
*
An AOR >1 indicates a significantly increased risk of prolonged pregnancy or preterm delivery whereas an AOR <1 indicates significantly less risk compared with women of normal weight (P < 0.05).