Maternal characteristics and factors and risk of relative microcephaly in the offspring
| Characteristic | Relative microcephaly | Non-microcephaly | Prevalence per 1000 | OR 95% CI | |
| Unadjusted | Adjusted* | ||||
| Maternal age (years) | |||||
| <25 | 24 | 5463 | 4.4 | 2.05 (1.18 to 3.42) | 1.26 (0.69 to 2.28) |
| 25–29 | 35 | 18 802 | 1.9 | 0.85 (0.52 to 1.38) | 0.91 (0.55 to 1.51) |
| 30–34 | 31 | 14 148 | 2.2 | 1.00 (reference) | 1.00 (reference) |
| ≥35 | 21 | 7139 | 2.9 | 1.34 (0.77 to 2.34) | 1.08 (0.61 to 1.93) |
| Education | |||||
| University/college | 37 | 27 512 | 1.3 | 1.00 (reference) | 1.00 (reference) |
| High school | 19 | 6765 | 2.8 | 2.09 (1.20 to 3.63) | 1.70 (0.95 to 3.03) |
| Elementary school | 55 | 11 275 | 4.9 | 3.63 (2.39 to 5.51) | 2.58 (1.60 to 4.08) |
| Primiparity | 85 | 37 013 | 2.3 | 0.75 (0.49 to 1.17) | 1.34 (0.80 to 2.25) |
| Cantonese ethnicity | 94 | 38 808 | 2.4 | 0.96 (0.57 to 1.61) | 1.11 (0.65 to 1.90) |
| IVF conception | 8 | 2659 | 3.0 | 1.25 (0.61 to 2.58) | 1.36 (0.64 to 2.90) |
| Congenital heart disease | 12 | 513 | 22.9 | 10.6 (5.8 to 19.5) | 3.41 (1.64 to 7.08) |
| Other congenital anomalies in offspring† | 4 | 480 | 8.3 | 3.51 (1.29 to 9.56) | 1.08 (0.35 to 3.33) |
| Intrauterine growth restriction | 33 | 402 | 75.9 | 47.5 (31.3 to 72.2) | 20.2 (12.2 to 33.5) |
| Maternal anomalies | 2 | 420 | 4.7 | 1.97 (0.49 to 8.01) | 1.23 (0.28 to 5.35) |
| Diabetes mellitus | 14 | 5484 | 2.5 | 1.06 (0.61 to 1.85) | 1.05 (0.58 to 1.84) |
| Pre-eclampsia | 27 | 1055 | 25.0 | 13.6 (8.75 to 21.0) | 5.28 (3.13 to 8.90) |
| Chronic illness | 15 | 6576 | 2.1 | 0.86 (0.49 to 1.50) | 0.71 (0.40 to 1.25) |
| Teratogens | 5 | 664 | 7.5 | 3.19 (1.30 to 7.85) | 1.32 (0.48 to 3.60) |
| TORCH agents‡ | 6 | 371 | 15.9 | 6.96 (3.04 to 15.9) | 2.96 (1.10 to 7.94) |
| Genital/reproductive infections | 1 | 719 | 1.4 | 0.57 (0.08 to 4.07) | 0.41 (0.06 to 3.07) |
| Overall | 111 | 45 552 | 2.4 | ||
*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.