Maternal exposures and risk of microcephaly in offspring
| Infants, N | Microcephaly, N | Prevalence per 10 000 | Prevalence difference per 10 000 (95% CI)* | Prevalence ratio (95% CI)* | |
| Age, years | |||||
| <25 | 420 786 | 206 | 4.90 | 0.90 (0.15 to 1.64) | 1.23 (1.04 to 1.46) |
| 25–34 | 1 273 000 | 474 | 3.72 | Reference | Reference |
| ≥35 | 251 018 | 114 | 4.54 | 0.56 (−0.34 to 1.45) | 1.21 (0.98 to 1.48) |
| Parity | |||||
| 0 | 1 099 953 | 490 | 4.45 | 0.96 (0.35 to 1.57) | 1.28 (1.08 to 1.51) |
| 1 | 609 017 | 206 | 3.38 | Reference | Reference |
| ≥2 | 214 654 | 86 | 4.01 | 0.66 (−0.31 to 1.63) | 1.16 (0.90 to 1.51) |
| Multiple birth | |||||
| Yes | 50 924 | 35 | 6.87 | 2.79 (0.53 to 5.05) | 1.73 (1.19 to 2.51) |
| No | 1 893 880 | 759 | 4.01 | Reference | Reference |
| Rural residence | |||||
| Yes | 373 791 | 118 | 3.16 | −1.57 (−2.25 to –0.88) | 0.63 (0.52 to 0.78) |
| No | 1 498 758 | 643 | 4.29 | Reference | Reference |
| Material deprivation | |||||
| Low | 343 820 | 116 | 3.37 | Reference | Reference |
| Low-moderate | 365 081 | 135 | 3.70 | 0.57 (−0.30 to 1.44) | 1.12 (0.87 to 1.44) |
| Moderate | 365 519 | 123 | 3.37 | 0.19 (−0.67 to 1.05) | 1.05 (0.81 to 1.36) |
| Moderate-high | 366 549 | 167 | 4.56 | 1.62 (0.68 to 2.56) | 1.47 (1.15 to 1.87) |
| High | 379 859 | 188 | 4.95 | 2.15 (1.18 to 3.12) | 1.66 (1.30 to 2.11) |
| Period | |||||
| 1989–1996 | 707 132 | 280 | 3.96 | Reference | Reference |
| 1997–2004 | 574 463 | 247 | 4.30 | 0.56 (−0.14 to 1.26) | 1.11 (0.93 to 1.33) |
| 2005–2012 | 663 209 | 267 | 4.03 | 0.53 (−0.14 to 1.20) | 1.04 (0.88 to 1.24) |
| Maternal anomaly† | |||||
| Yes | 36 674 | 31 | 8.45 | 3.84 (0.88 to 6.80) | 2.11 (1.46 to 3.05) |
| No | 1 908 130 | 763 | 4.00 | Reference | Reference |
| Diabetes | |||||
| Yes | 40 294 | 25 | 6.20 | 2.03 (−0.37 to 4.43) | 1.49 (1.00 to 2.22) |
| No | 1 904 510 | 769 | 4.04 | Reference | Reference |
| Teratogen‡ | |||||
| Yes | 48 562 | 62 | 12.77 | 8.53 (5.35 to 11.72) | 3.10 (2.37 to 4.07) |
| No | 1 896 242 | 732 | 3.86 | Reference | Reference |
| TORCH§ | |||||
| Yes | 2617 | 32 | 112.28 | 118.21 (75.85 to 160.58) | 32.38 (22.42 to 46.75) |
| No | 1 942 187 | 762 | 3.92 | Reference | Reference |
| Total | 1 944 804 | 794 | 4.08 | – |
↵*Models contain maternal risk factors as exposures and microcephaly as the outcome, and are adjusted for maternal age, parity, multiple birth, rural residence, material deprivation and period.
†Maternal congenital anomalies and errors of metabolism.
‡History of epilepsy, alcohol or drug abuse.
§Maternal infections including toxoplasmosis, rubella, cytomegalovirus, herpes, other.