Table 2.
Studies reporting specific risks associated with maternal obesity
| Complication | First author and study design | Risk of complication (odds ratio 95% confidence interval, unless otherwise stated) |
|---|---|---|
| Antenatal | ||
| Miscarriage | Lashen26 Nested case-control study of 1644 obese and 3288 age-matched normal weight controls. UK | OR of early miscarriage for obese 1.2 (1.01–1.46) and recurrent early miscarriage 3.5 (1.03–12.01) |
| Mulders27 Meta-analysis of outcomes associated with ovulation induction with gonadotrophins. Obese versus non-obese | Pooled OR of spontaneous miscarriage for obese 3.05 (1.45–6.44) | |
| Fetal anomalies | Anderson39 Population-based case-control study of 477 infants with birth defects and 497 controls (live infants without abnormalities). Obese versus normal weight. USA | AOR of anencephaly for obese 2.3 (1.2–4.3), spina bifida 2.8 (1.7–4.5), isolated hydrocephaly 2.7 (1.5–5.0) |
| Callaway11 Observational study of 14,230 singleton pregnancies. Overweight, obese and morbidly obese versus normal weight. Australia | AOR of birth defects for overweight 1.26 (0.85–1.87) NS, obese 1.58 (1.02–2.46), morbidly obese 3.41 (1.67–6.94) | |
| Cedergren30 Case-control study of 6801 women who had infants with cardiovascular defect and 812,457 controls (all delivered women). Obese and morbidly obese (>35) versus normal weight. Sweden | AOR of cardiovascular defects for obese 1.18 (1.09–1.27), morbidly obese 1.41 (1.22–1.64). AOR of severe types of cardiovascular defects for obese 1.23 (1.05–1.44), morbidly obese 1.69 (1.27–2.26) | |
| Rasmussen40 Meta-analysis of 12 studies (4 cohort and 8 case-control), including 8962 women. Overweight, obese and severely obese versus normal-weight women | OR of neural tube defect-affected pregnancy for overweight 1.22 (0.99–1.49), obese 1.70 (1.34–2.15) and severely obese 3.11 (1.75–5.46) | |
| Watkins29 Case-control study of approximately 40,000 births per year between 1993 and1997. Obese women versus normal-weight women. USA | OR of spina bifida for obese 3.5 (1.2–10.3), omphalocele 3.3 (1.0–10.3), heart defects 2.0 (1.2–3.4) | |
| Gestational diabetes mellitus | Bianco41 Retrospective cohort study of 11,926 singleton pregnancies resulting in live births. BMI ≥35 versus BMI 19–27. USA | OR of GDM for BMI ≥35 3.2 (2.5–4.2) |
| Callaway11 See above | AOR of GDM for overweight 1.78 (1.25–2.52), obese 2.95 (2.05–4.25), morbidly obese 7.44 (4.42–12.54) | |
| Sebire10 Retrospective observational study of 287,213 completed singleton pregnancies. Overweight and obese versus normal weight. UK | AOR of GDM for overweight 1.68 (99% CI 1.53–1.84), obese 3.6 (3.25–3.98) | |
| Hypertension and preeclampsia | Bianco41 See above | OR of pregnancy induced hypertension for BMI ≥35 3.6 (2.7–4.8) |
| Callaway11 See above | AOR of hypertensive disorders of pregnancy for overweight 1.74 (1.45–2.15), obese 3.00 (2.40–3.74)], morbidly obese 4.87 (3.27–7.24) | |
| Cedergren14 Population-based cohort study of 12,698 women with BMI 35.1–40.0 and 3480 women with morbid obesity (BMI >40), compared with 535,900 normal-weight women (BMI 19.8–26.0). Sweden | AOR of pre-eclampsia for BMI 35–40 3.90 (3.54, 4.30), morbidly obese 4.82 (4.04–5.74) | |
| O'Brien13 Systematic overview of 13 cohort studies, including nearly 1.4 million women | Risk of preeclampsia typically doubled with each 5–7 kg/m2 increase in prepregnancy body mass index | |
| Sattar7 Prospective observational study of 1142 singleton pregnancies. Waist circumference ≥80 cms versus ≤80 cms, and BMI ≥25 versus ≤25 cm. UK | OR of pregnancy-induced hypertension for women with waist circumference ≥80 cm 1.8 (1.1–2.9), BMI ≥25 2.0 (1.2–3.4) | |
| OR of preeclampsia for women with waist circumference ≥80 cm 2.7 (1.1–6.8), BMI ≥25 1.9 (0.7–4.8) | ||
| Sebire10 See above | AOR of preeclampsia for overweight 1.44 (99% CI 1.28–1.62), obese 2.14 (1.85–2.47) | |
| Venous thromboembolism | Jacobsen20 Hospital-based case-control study of 559 cases with no prior VTE and 1229 controls. Cases were women with objectively verified VTE during pregnancy or postpartum. Norway | AOR for antenatal VTE: BMI ≥25 with no immobilization 1.8 (1.3–2.4), BMI ≥25 with immobilization 62.3 (11.5–337.6) |
| AOR for postpartum VTE: BMI ≥25 with no antenatal immobilization 2.4 (1.7–3.3), BMI ≥25 with immobilization 40.1 (8.0–201.5) | ||
| Larsen17 Population-based case-control study including 129 VTE cases and 258 controls. Overweight and obese versus normal weight. Denmark | AOR of VTE during pregnancy for overweight 1.6 (0.6–4.4), obese 9.7 (3.1–30.8) | |
| Maternal death | CEMACH16 Confidential enquiry into all maternal deaths in the UK between 2003 and 2005. UK | Of women with a known BMI, 31.3% who died of causes directly related to their pregnancy had a BMI ≥30. Of women dying of indirect causes (not due to direct obstetric causes), 25.0% had a BMI ≥30 |
| Intrapartum | ||
| Failure to progress in labour | Bianco41 See above | OR of failure to progress for BMI ≥35 2.6 (2.0–3.5) |
| Induction of labour | Sebire10 See above | AOR of induction of labour for overweight 1.27 (99% CI 1.123–1.30), obese 1.70 (1.64–1.76) |
| Usha Kiran35 Population-based observational study including 8350 singleton uncomplicated pregnancies with cephalic presentation of ≥37 weeks. Obese (BMI ≥30) versus normal weight (BMI <29). UK | OR of postdates for obese 1.4 (1.2–1.7), induction of labour 1.6 (1.3–1.9) | |
| Shoulder dystocia | Cedergren14 See above | AOR of shoulder dystocia for morbidly obese 3.14 (1.86–5.31) |
| Usha Kiran35 See above | OR of shoulder dystocia for obese 2.9 (1.4–5.8) | |
| Caesarean | Bianco41 See above | AOR of caesarean for BMI ≥35 2.3 (1.9–2.8) |
| Callaway11 See above | AOR of caesarean for overweight 1.50 (1.36–1.66), obese 2.02 (1.79–2.28), and morbidly obese 2.54 (1.94–3.32) | |
| Chu22 Meta-analysis including 33 studies. Overweight, obese and severely obese versus normal weight | OR of caesarean for overweight 1.46 (1.34–1.60), obese 2.05 (1.86–2.27) and severely obese 2.89 (2.28–3.79) | |
| Sebire10 See above | AOR of emergency caesarean section for overweight 1.30 (99% CI 1.25–1.34), obese 1.83 (1.74–1.93) | |
| Usha Kiran35 See above | OR of emergency caesarean for obese 2.0 (1.2–3.5) | |
| Macrosomia | Cedergren14 See above | AOR of large for gestational age for BMI 35–40 3.11 (2.96–3.27), morbidly obese 3.82 (3.50–4.16) |
| Sebire10 See above | AOR of birth weight above 90th centile for overweight 1.57 (99% CI 1.50–1.64), obese 2.36 (2.23–2.50) | |
| Usha Kiran35 See above | OR of macrosomia for obese 2.1 (1.6–2.6) | |
| Prematurity | Callaway11 See above | AOR of prematurity (<34 weeks) for overweight 1.22 (0.90–1.64), obese 1.16 (0.81–1.67), morbidly obese 2.13 (1.13–4.01) |
| Stillbirth | Cedergren14 See above | AOR of stillbirth for BMI 35–40 1.99 (1.57–2.51), morbidly obese 2.79 (1.94–4.02) |
| Chu28 Meta-analysis including nine studies (6 cohort, 3 case-control). Overweight and obese versus normal weight | OR of stillbirth for overweight 1.47 (1.08–1.94), obese 2.07 (1.59–2.74) | |
| Kristensen42 Cohort study of 24,505 singleton pregnancies (112 stillbirths, 75 neonatal deaths) (Denmark). Obese versus normal weight. Denmark | AOR of stillbirth for obese 3.1 (1.6–5.9) | |
| Sebire10 See above | AOR of stillbirth for overweight 1.10 (99% CI 0.94–1.28), obese 1.40 (1.14–1.71) | |
| Postnatal | ||
| Low APGAR scores | Sebire10 See above | AOR of a low APGAR score for overweight 1.16 (99% CI 1.06–1.28), obese 1.45 (1.28–1.64) |
| Admission to neonatal intensive care units | Bianco41 See above | OR of admissions for BMI ≥35 1.2 (1.0–1.3) |
| Callaway11 See above | AOR of admissions for overweight 0.92 (0.73–1.16), obese 1.25 (0.97–1.62), morbidly obese 2.77 (1.81–4.25) | |
| Sebire10 See above | AOR of admissions for overweight 1.22 (99% CI 1.16–1.28), obese 1.34 (1.25–1.44) | |
| Usha Kiran35 See above | OR of admissions for obese 1.5 (1.09–2.3) | |
| Neonatal death | Cedergren14 See above | AOR of early neonatal death for BMI 35.1–40 2.09 (1.50–2.91), morbidly obese 3.41 (2.07–5.63) |
| Kristensen42 See above | AOR of neonatal death for obese 2.7 (1.2–6.1) | |
| Shah43 Population-based observational study of 30,167 (181 stillbirths and 78 neonatal deaths) singleton pregnancies. Obese versus BMI < 29. UK | OR of early neonatal death for obese 1.66 (1.0–2.75) | |
| Postpartum haemorrhage | Sebire10 See above | AOR of postpartum haemorrhage section for overweight 1.16 (99% CI 1.12–1.21), obese 1.39 (1.32–1.46) |
| Usha Kiran35 See above | OR of blood loss >500 mL for obese 1.5 (1.2–1.8) | |
| Urine, uterine and wound infection | Sebire10 See above | AOR of genital tract infection for overweight 1.24 (99% CI 1.09–1.41), obese 1.30 (1.07–1.56) |
| AOR of urinary tract infection for overweight 1.17 (1.04–1.33), obese 1.39 (1.18–1.63) | ||
| AOR of wound infection for overweight 1.27 (1.09–1.48), obese 2.24 (1.91–2.64) | ||
| Usha Kiran35 See above | OR of urinary tract infections for obese 1.9 (1.1–3.4) | |
| Venous thromboembolism | Larsen17 See above | AOR of postpartum VTE for overweight 1.3 (0.5–3.3), obese 2.8 (0.8–9.8) |
| Reduced breastfeeding success | Sebire10 See above | AOR of breastfeeding at discharge for overweight 0.86 (99% CI 0.84–0.88), obese 0.58 (0.56–0.60) |
OR = odds ratio; AOR = adjusted odds ratio; NS = non-significant; BMI = body mass index; CI = confidence interval; VTE = venous thromboembolism; GDM = gestational diabetes mellitus; CEMACH = Confidential Enquiry into Maternal and Child Health