Risk factors associated with neonatal encephalopathy in univariable analysis and after adjustment for preconception, antepartum and intrapartum factors
| Risk factor | Cases n (%) | Controls n (%) | Unadjusted OR (n=620) | 95% CI | Adjusted OR‡‡ (n=614) | 95% CI |
| Sociodemographic factors | ||||||
| Socioeconomic group | ||||||
| High | 33/209 (15.8) | 82/405 (20.3) | 1.00 | – | 1.00 | – |
| Medium | 131/209 (62.7) | 245/405 (60.5) | 1.64 | 0.87 to 3.11 | 1.52 | 0.81 to 2.34 |
| Low | 45/209 (21.5) | 78/405 (19.3) | 1.46 | 0.83 to 2.47 | 1.39 | 0.64 to 3.01 |
| Preconception factors | ||||||
| Maternal age <20 years | 61/210 (29.1) | 76/408 (18.6) | 1.79 | 1.21 to 2.64 | 1.28 | 0.70 to 2.50 |
| Maternal weight <50 kg | 31/208 (14.9) | 34/401 (8.5) | 1.89 | 1.13 to 3.18 | 0.69 | 0.32 to 1.61 |
| Maternal height <150 cm | 40/208 (19.2) | 44/399 (11.0) | 1.92 | 1.21 to 3.06 | 1.48 | 0.73 to 3.00 |
| Antepartum factors | ||||||
| Primiparity | 123/210 (58.6) | 183/409 (44.7) | 1.75 | 1.25 to 2.44 | 1.56 | 0.86 to 2.84 |
| ≥4 Antenatal visits | 99/210 (47.1) | 225/408 (55.2) | 0.73 | 0.52 to 1.01 | 0.96 | 0.60 to 1.52 |
| Previous ‘birth asphyxia’ | 20/87 (23.0) | 33/226 (14.6) | 1.75 | 0.94 to 3.25 | 1.27 | 0.50 to 3.21 |
| Previous perinatal death | 24/87 (27.6) | 44/226 (19.5) | 1.58 | 0.89 to 2.80 | 1.22 | 0.52 to 2.91 |
| Severe anaemia during pregnancy* | 10/209 (4.8) | 5/408 (1.2) | 4.05 | 1.37 to 12.01 | 4.38 | 0.97 to 19.82 |
| Hypertension during pregnancy† | 18/210 (8.6) | 17/408 (4.2) | 2.16 | 1.09 to 4.28 | 3.77 | 1.49 to 9.55 |
| Maternal HIV-positive | 15/210 (7.1) | 53/409 (13.0) | 0.52 | 0.28 to 0.94 | 0.57 | 0.24 to 1.32 |
| Infant factors | ||||||
| Male | 136/210 (64.8) | 196/409 (47.9) | 2.00 | 1.42 to 2.82 | 2.51 | 1.55 to 4.07 |
| Birth weight <2.5 kg | 11/209 (5.3) | 27/409 (6.6) | 0.81 | 0.39 to 1.67 | 0.46 | 0.15 to 1.44 |
| Birth weight >4.0 kg | 12/209 (5.7) | 12/409 (2.9) | 2.00 | 0.88 to 4.51 | 2.17 | 0.77 to 6.13 |
| Large head circumference‡ | 21/191 (11.0) | 12/400 (3.0) | 3.99 | 1.92 to 8.30 | 2.28 | 0.59 to 6.22 |
| Twins | 5/210 (2.4) | 13/409 (3.2) | 0.74 | 0.26 to 2.11 | 0.58 | 0.13 to 2.61 |
| Non-cephalic presentation | 23/209 (11.0) | 11/409 (2.7) | 4.47 | 2.14 to 9.37 | 5.74 | 2.01 to 16.41 |
| Intrapartum factors | ||||||
| Augmentation of labour | 42/209 (20.1) | 43/408 (10·5) | 2.13 | 1.34 to 3.39 | 2.23 | 1.17 to 4.23 |
| No auscultation of fetal heart rate during labour | 114/208 (54.8) | 115/408 (28·2) | 3.09 | 2.18 to 4.38 | 2.75 | 1.71 to 4.22 |
| Prolonged rupture of membranes§ | 21/193 (10.9) | 15/396 (3·8) | 3.10 | 1.56 to 6.16 | 2.44 | 0.90 to 6.60 |
| Acute intrapartum event¶ | 8/210 (3.8) | 4/409 (1·0) | 4.01 | 1.19 to 13.47 | 8.74 | 1.70 to 45.02 |
| Obstructed labour** | 65/181 (31.9) | 33/407 (8·1) | 6.35 | 4.00 to 10.14 | 3.80 | 1.96 to 7.36 |
| Prolonged labour†† | 100/190 (52.6) | 157/387 (40·6) | 1.63 | 1.15 to 2.31 | 0.81 | 0.47 to 1.39 |
| Meconium-stained liquor | 55/121 (45.5) | 19/359 (5·3) | 14.91 | 8.31 to 26.75 | # | – |
| Elective caesarean section | 0/209 (0.0) | 3/409 (0·7) | – | – | # | – |
| Emergency caesarean section | 50/209 (23.9) | 56/409 (13·7) | 1.98 | 1.30 to 3.03 | # | – |
*Defined as haemoglobin ≤7 g/dL during pregnancy and documented in the clinical record.
† Defined as systolic blood pressure >140 mm Hg or diastolic >90 mm Hg developing after 20 weeks’ gestation.
‡Defined as >97th centile in the control population (37.9 cm).
§ Defined as rupture ≥24 hours.
¶ Defined as antepartum haemorrhage, cord prolapse or uterine rupture.
** Defined as labour with no advance of the presenting part despite strong, regular uterine contractions as documented in the intrapartum record.
†† Defined as >24 hours in primiparity and >12 hours in multiparity.
‡‡ Adjusted for all other variables in the table plus maternal C reactive protein >90th centile and neonatal bacteraemia. Factors considered a consequence of intrapartum events (#) were not included in the model.