Table 1

Cases of sudden infant death syndrome (SIDS), sudden intrauterine unexplained death (SIUD), and surviving controls by basic and clinical variables

	SIDS		SIUD		Controls
Variable	Number	Valid %	Number	Valid %	Number	Valid %
Crude numbers are presented together with the percentage of valid registrations. *Date of birth is used in surviving controls.
Age at last menstruation
<25 years	32	42.7	18	23.6	154	26.5
25–29	25	33.3	28	36.8	215	36.9
30–35	13	17.3	22	28.9	154	26.5
>35 years	5	6.7	8	10.5	59	10.1
Maternal smoking
No	27	41.5	43	62.3	396	74.9
1–9 cigarettes/day	11	16.9	10	13.2	92	17.4
≥10 cigarettes/day	27	41.5	16	21.1	41	7.8
Maternal parity
0 births	20	28.2	37	52.1	308	53.8
1 birth	29	40.8	24	33.8	176	30.8
2 births	15	21.1	3	4.2	58	10.1
3 births	6	8.5	4	5.6	18	3.1
4+ births	1	1.4	3	4.2	12	2.0
Previous stillbirths or abortions	10	14.3	10	14.1	94	16.4
Previous induced abortions	19	26.8	15	20.8	135	23.5
Body mass index >25 kg/m²	8	13.1	17	27.0	56	11.7
Ethnic origin Europe (EU)	71	97.2	62	85.0	468	85.1
Education
<10 years	18	32.1	16	28.6	69	15.9
10–12	23	41.1	21	37.5	151	34.9
>12 years	15	26.8	19	33.9	213	49.2
Glucosuria	9	14.1	13	18.8	97	16.8
Proteinuria	16	24.2	12	17.4	66	11.5
Abnormally high fundal height	28	45.9	27	41.5	188	34.2
Abnormally low fundal height	5	8.2	8	12.3	30	5.5
Male	52	66.7	40	54.8	296	50.9
Death autumn/winter*	53	69.7	41	53.9	281	48.3
Preterm birth (<38 weeks)	10	13.3	37	48.7	35	6.0
Unrelated parents	78	100.0	68	94.4	558	96.9