Table 1. Estimated age-specific annual numbers of parvovirus B19 infections and associated complications among women at child-bearing age in Japan.

Age group (years)	No. females	No. maternities	Total infections	Infections during pregnancy	Fetal deaths	Hydrops fetalis
15–19	2,958,000	13,273	156 (0–6,585)	1 (0–30)	0 (0–1)	0 (0–1)
20–24	3,116,000	104,053	164 (0–6,736)	5 (0–225)	0 (0–10)	0 (0–2)
25–29	3,546,000	300,350	187 (0–7,445)	16 (0–631)	1 (0–28)	0 (0–5)
30–34	3,987,000	373,452	210 (0–8,129)	20 (0–761)	1 (0–34)	0 (0–7)
35–39	4,785,000	221,245	251 (0–9,475)	12 (0–438)	1 (0–20)	0 (0–4)
40–44	4,609,000	37,435	8 (0–35,597)	0 (0–289)	0 (0–13)	0 (0–3)
Total	23,001,000	1,049,808	976 (0–73,967)	54 (0–2,374)	3 (0–107)	0 (0–21)

Maximum likelihood estimates with the 95% confidence intervals (inside parentheses) are shown for the right four columns. The 95% confidence intervals for the estimated force of infection based on a piecewise constant model were used: i.e., 0–0.0059 for those aged 15–39 years and 0–0.0246 for those aged 40 years and older. Risks of fetal death from gestational week 1–20 and hydrops fetalis from week 9–20 were assumed to be 9.0% and 2.9%, respectively [8], [25].