Table 1.

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 Toxoplasma gondii only.

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