Crude and adjusted risks of obstetric complications in the different BMI groups compared to normal (OR 1)
Characteristics
 		 OR (95% CI)
 		 Underweight
BMI < 20
n = 2842
 		 Overweight
BM I= 25–29.9
n = 5308
 		 Obese
BMI = 30–34.9
n = 1858
 		 Morbidly Obese
BMI > 35
n = 157
 
Pre-eclampsia*
 		 Crude
 		 0.7(0.5–0.8)
 		 1.7(1.4–1.9)
 		 3.3(2.7–3.9)
 		 7.4(4.8–11.5)
 

 		 Adjusted
 		 0.6(0.5–0.7)
 		 1.6(1.2–1.8)
 		 3.1(2.8–3.5)
 		 7.2(4.7–11.2)
 
Gestational hypertension*
 		 Crude
 		 0.6(0.5–0.7)
 		 1.6(1.5–1.8)
 		 2.4(2.2–2.7)
 		 3.0(2.1–4.2)
 

 		 Adjusted
 		 07(0.6–0.8)
 		 1.5(1.4–1.7)
 		 2.2(2.1–2.6)
 		 3.1(2.0–4.3)
 
Induced labour*
 		 Crude
 		 0.8(0.7–0.9)
 		 1.3(1.2–1.4)
 		 2.0(1.8–2.2)
 		 2.6(1.9–3.5)
 

 		 Adjusted
 		 0.8(0.8–0.9)
 		 1.3(1.2–1.4)
 		 1.8(1.6–2.0)
 		 1.8(1.3–2.5)
 
Elective C-section
 		 Crude
 		 0.7(0.6–0.9)*
 		 1.2(1.0–1.4)
 		 1.4(1.1–1.8)*
 		 3.2(1.9–5.3)*
 

 		 Adjusted
 		 0.8(0.6–1.0)
 		 1.1(0.9–1.3)
 		 1.4(1.0–1.8)
 		 3.1(1.7–6.1)*
 
Emergency CS
 		 Crude
 		 0.9(0.9–1.0)
 		 1.7(1.5–1.8)*
 		 2.4(2.1–2.7)*
 		 3.2(2.3–4.5)*
 

 		 Adjusted
 		 0.9(0.8–1.1)
 		 1.5(1.3–1.6)*
 		 2.0(1.8–2.3)*
 		 2.8(2.0–3.9)*
 
Postpartum hge
 		 Crude
 		 0.7(0.6–0.8)*
 		 1.4(1.3–1.6)*
 		 2.3(2.1–2.6)*
 		 2.9(2.0–4.2)*
 

 		 Adjusted
 		 0.8(0.7–1.0)
 		 1.1(1.0–1.2)
 		 1.5(1.3–1.7)*
 		 1.3(0.8–1.9)
 
Preterm delivery (< 37 weeks)
 		 Crude
 		 1.1(0.9–1.3)
 		 1.0(0.9–1.1)
 		 1.2(1.1–1.4)*
 		 2.1(1.4–3.1)*
 

 		 Adjusted
 		 1.0(0.9–1.3)
 		 1.0(0.9–1.1)
 		 1.2(1.0–1.4)
 		 1.6(1.0–2.7)
 
Preterm delivery (< 33 weeks)
 		 Crude
 		 0.9(0.7–1.2)
 		 1.0(0.8–1.2)
 		 1.8(1.4–2.3)*
 		 2.8(1.4–5.4)*
 

 		 Adjusted
 		 0.9(0.7–1.1)
 		 1.0(0.8–1.1)
 		 2.0(1.3–2.9)*
 		 2.0(0.8–4.9)
 
Spont. Preterm (< 37 weeks)
 		 Crude
 		 1.4(1.1–1.9)
 		 0.8(0.6–1.0)
 		 0.9(0.5–1.1)
 		 1.3(1.1–2.8)
 

 		 Adjusted
 		 1.4(1.1–1.9)
 		 0.8(0.6–1.1)
 		 1.0(0.5–1.2)
 		 1.2(1.1–2.8)
 
Post term (> 41 weeks)
 		 Crude
 		 0.7(0.6–0.8)*
 		 1.2(1.1–1.3)*
 		 1.4(1.1–1.6)*
 		 0.8 (0.4–1.7)
 

 		 Adjusted
 		 0.9(0.7–1.1)
 		 0.9(0.8–1.1)
 		 0.9(0.7–1.1)
 		 0.8(0.4–1.8)
 
Stillbirth
 		 Crude
 		 0.8(0.5–1.3)
 		 1.2(0.9–1.6)
 		 2.0(1.4–3.0)
 		 2.8(1.0–7.6)
 

 		 Adjusted
 		 1.0(0.6–1.6)
 		 1.3(0.9–1.9)
 		 1.8 (1.1–2.9)*
 		 1.1(0.3–4.1)
 
Birth weight < 2500 g
 		 Crude
 		 1.4(1.2–1.6)*
 		 0.9(0.7–1.0)
 		 1.1(0.9–1.3)
 		 1.8(1.1–3.0)*
 

 		 Adjusted
 		 1.7(1.2–2.0)*
 		 0.9(0.7–1.1)
 		 1.1(0.9–1.3)
 		 0.7(0.4–1.5)
 
Birth weight > 4000 g*
 		 Crude
 		 0.4(0.4–0.6)
 		 1.4(1.3–1.6)
 		 1.9(1.7–2.2)
 		 2.3(1.5–3.5)
 

 		 Adjusted
 		 0.5(0.4–0.6)
 		 1.4(1.3–1.6)
 		 1.9(1.6–2.2)
 		 2.1(1.3–3.2)
 

*P value less than 0.05

All variables adjusted for relevant sociodemographic characteristics and year of delivery; induced labour, preterm delivery and caesarean section also adjusted for pre-eclampsia and gestational hypertension; postpartum haemorrhage for induction of labour and caesarean section; birthweight for gestational age and sex

Bhattacharya et al. BMC Public Health 2007 7:168   doi:10.1186/1471-2458-7-168. http://www.biomedcentral.com/1471-2458/7/168

© 2007 Bhattacharya et al; licensee BioMed Central Ltd.
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