| Body mass index (BMI) at booking (kg/m2) | Average rate of intrapartum caesarean birth (category 1, 2 or 3) | Average rate of stillbirth, neonatal death or the baby needing neonatal care | Average rate of birth with forceps or ventouse |
|---|---|---|---|
| Less than 18.5 | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 |
| 18.5 to 24.9 | 95 per 1,000 (so this does not happen in about 905 pregnancies per 1,000) | 28 per 1,000 (so this does not happen in about 972 pregnancies per 1,000) | 156 per 1,000 (so this does not happen in about 844 pregnancies per 1,000) |
| 25 to 29.9 | 123 per 1,000 (so this does not happen in about 877 pregnancies per 1,000). This is an average increase of 28 per 1,000 compared with women with a BMI 18.5 to 24.9 kg/m2 (so for about 972 pregnancies per 1,000, the outcome was the same) | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 |
| 30 to 35 | 133 per 1,000 (so this does not happen in about 867 pregnancies per 1,000). This is an average increase of 38 per 1,000 compared with women with a BMI 18.5 to 24.9 kg/m2 (so for about 962 pregnancies per 1,000, the outcome was the same) | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 | No difference compared with women with a BMI 18.5 to 24.9 kg/m2 |
| More than 35 | 137 per 1,000 (so this does not happen in about 863 pregnancies per 1,000). This is an average increase of 42 per 1,000 compared with women with a BMI 18.5 to 24.9 kg/m2 (so for about 958 pregnancies per 1,000, the outcome was the same) | 51 per 1,000 (so this does not happen in about 949 pregnancies per 1,000). This is an average increase of 23 per 1,000 compared with women with a BMI 18.5 to 24.9 kg/m2 (so for about 977 pregnancies per 1,000, the outcome was the same) | 85 per 1,000 (so this does not happen in 915 pregnancies per 1,000). This is a decrease of 71 per 1,000 compared with women with a BMI 18.5 to 24.9 kg/m2 (so for about 929 pregnancies per 1,000, the outcome was the same) |
Source: evidence review A: impact of BMI on choice of place of birth. For more details on risks identified in different settings, see evidence review A.
From: Intrapartum care
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