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Table 3 Crude and adjusted risks of obstetric complications in the different BMI groups compared to normal (OR 1)

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

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)

  1. *P value less than 0.05
  2. 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