Table 1. Comparison of the parental ages from all childbearing married couples in Switzerland and from couples of the two independent study groups with a child with trisomy 13, 18 and 21.

			Trisomy 21			Postnatal (N=559)			Trisomy 13 and 18 (N=212)			Combine trisomies (N=969)
Mother's age group	Live births in Switzerland from 1979 to 2006 (N=1 932 226)		Prenatal (N=198)
	M.≥F.	M.<F.	M.≥F.	M.<F.	Odds ratio (99.4% CI)	M.≥F.	M.<F.	Odds ratio (99.4% CI)	M.≥F.	M.<F.	Odds ratio (99.4% CI)	M.≥F.	M.<F.	Odds ratio (99.4% CI)
10–14	0	0	0	0		0	1		0	0		0	1
15–19	106	16 270	0	0		1	7	21.9 (1.1–429.1) P 0.05	0	2	0.0 (0-NaN) P 1.00	1	9	17.1 (0.9–320.3) P 0.06
20–24	11 787	259 647	0	4	0.0 (0-NaN) P 1.00	6	43	3.1 (0.9–10.3) P 0.02	0	11	0.0 (0-NaN) P 1.00	6	58	2.3 (0.7–7.5) P 0.06
25–29	73 018	630 515	3	19	1.4 (0.2–7.6) P 0.49	20	100	1.7 (0.9–3.4) P 0.03	15	47	2.8 (1.2–6.3) P 0.001*	38	166	2.0 (1.2–3.3) P 0.0005*
30–34	132 643	518 743	7	24	1.1 (0.3–3.8) P 0.82	64	120	2.1 (1.4–3.2) P 0.00001*	12	47	1.0 (0.4–2.4) P 1.0	83	191	1.7 (1.2–2.4) P 0.0001*
35–39	80 795	167 745	28	48	1.2 (0.6–2.3) P 0.46	61	74	1.7 (1.1–2.8) P 0.002*	22	24	1.9 (0.8–4.3) P 0.04	111	146	1.6 (1.1–2.2) P 0.0004*
40–44	16 614	22 559	21	41	0.7 (0.3–1.5) P 0.20	32	17	2.6 (1.1–5.9) P 0.001*	19	9	2.9 (0.9–8.8) P 0.007	72	67	1.5 (0.9–2.3) P 0.03
45–49	762	928	1	2	0.6 (0.0–18.2) P 1.00	8	4	2.4 (0.4–13.4) P 0.16	3	1	3.7 (0.1–89.8) P 0.33	12	7	2.1 (0.6–7.9) P 0.16
50-	65	29	0	0		1	0		0	0		1	0

Comparison of the parental ages: in the first group the mother's age is at least as much as the fathers age (M.≥F.) and in the second group the father is older (M.<F.). Confidence intervals are indicated for the Bonferroni-corrected significance level α0=α/9=0.0056 (‘*' indicates significance after Bonferroni correction). Bold values indicate level of significance.