Maternal characteristics and factors and risk of absolute microcephaly in the offspring
| Characteristic | Absolute microcephaly | Non-microcephaly | Prevalence per 1000 | OR 95% CI | |
| Unadjusted | Adjusted* | ||||
| Maternal age (years) | |||||
| <25 | 31 | 5 244 | 5.9 | 2.14 (1.33 to 3.44) | 1.51 (0.90 to 2.53) |
| 25–29 | 51 | 18 263 | 2.8 | 1.01 (0.66 to 1.54) | 0.92 (0.59 to 1.41) |
| 30–34 | 38 | 13 730 | 2.8 | 1.00 (reference) | 1.00 (reference) |
| ≥35 | 9 | 6 899 | 1.3 | 0.47 (0.23 to 0.98) | 0.47 (0.23 to 0.99) |
| Education | |||||
| University/college | 61 | 26 775 | 2.3 | 1.00 (reference) | 1.00 (reference) |
| High school | 22 | 6 576 | 3.3 | 1.47 (0.90 to 2.39) | 1.27 (0.72 to 2.11) |
| Elementary school | 46 | 10 785 | 4.2 | 1.87 (1.28 to 2.75) | 1.57 (1.02 to 2.40) |
| Primiparity | 105 | 35 902 | 2.9 | 1.00 (0.64 to 1.56) | 1.42 (0.87 to 2.32) |
| Cantonese ethnicity | 110 | 37 591 | 2.9 | 1.01 (0.62 to 1.64) | 0.95 (0.57 to 1.56) |
| IVF conception | 7 | 2 576 | 2.9 | 0.93 (0.43 to 1.99) | 1.12 (0.51 to 2.46) |
| Congenital heart disease | 6 | 445 | 13.5 | 4.79 (2.10 to 10.93) | 2.33 (0.97 to 5.63) |
| Other congenital anomalies in offspring† | 3 | 440 | 6.8 | 2.37 (0.75 to 7.46) | 1.33 (0.38 to 4.67) |
| Intrauterine growth restriction | 6 | 212 | 27.5 | 10.1 (4.41 to 23.2) | 4.92 (2.04 to 11.9) |
| Maternal anomalies | 3 | 390 | 7.6 | 2.67 (0.85 to 8.43) | 2.34 (0.73 to 7.53) |
| Diabetes mellitus | 10 | 5311 | 1.9 | 0.61 (0.32 to 1.17) | 0.75 (0.39 to 1.44) |
| Pre-eclampsia | 8 | 863 | 9.2 | 3.32 (1.62 to 6.80) | 2.64 (1.25 to 5.59) |
| Chronic illness | 24 | 6303 | 3.8 | 1.37 (0.88 to 2.14) | 1.43 (0.91 to 2.24) |
| Teratogens | 8 | 626 | 12.6 | 4.60 (2.24 to 9.44) | 4.18 (1.98 to 8.77) |
| TORCH agents‡ | 4 | 324 | 12.2 | 4.33 (1.59 to 11.8) | 3.21 (1.09 to 9.49) |
| Genital/reproductive infections | 1 | 688 | 1.5 | 0.49 (0.07 to 3.53) | 0.57 (0.07 to 4.16) |
| Overall | 129 | 44 136 | 2.9 | ||
*Adjusted for infant birth year.
†Exclusive of congenital heart disease and CNS anomalies.
‡Latent T oxoplasma gondii only.
CNS, central nervous system; IVF, in vitro fertilisation; TORCH, Toxoplasma gondii, rubella virus, cytomegalovirus, herpes simplex virus.