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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