Table 2.

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 Toxoplasma gondii only.

CNS, central nervous system; IVF, in vitro fertilisation; TORCH, Toxoplasma gondii, rubella virus, cytomegalovirus, herpes simplex virus.