A parsimonious explanation for intersecting perinatal mortality curves: understanding the effect of plurality and of parity

Table 2 Numbers and rates of live births, stillbirths and early neonatal deaths among twin births, Canada (excluding Ontario), 1991 to 1997.

Gestational age	Stillbirths	Live births	Early neonatal deaths	Stillbirth rate (1)†	Early neonatal death rate (1)†	Perinatal mortality rate (1)†	Fetuses at risk	Stillbirth rate (2)†	Early neonatal death rate (2)†	Perinatal mortality rate (2)†
32	33	1,182	20	27.2	16.9	43.6	31,821	1.0	0.6	1.7
33	29	1,407	14	20.2	10.0	29.9	30,606	0.9	0.5	1.4
34	42	2,513	16	16.4	6.4	22.7	29,170	1.4	0.6	2.0
35	28	3,302	9	8.4	2.7	11.1	26,615	1.1	0.3	1.4
36	28	5,372	15	5.2	2.8	8.0	23,285	1.2	0.6	1.9
37	29	6,835	10	4.2	1.5	5.7	17,885	1.6	0.6	2.2
38	30	6,720	8	4.4	1.2	5.6	11,021	2.7	0.7	3.5
39	15	2,843	7	5.2	2.5	7.7	4,271	3.5	1.6	5.2
40	11	1,246	2	8.8	1.6	10.3	1,413	7.8	1.4	9.2
41	1	129	0	7.7	0.0	7.7	156	6.4	0.0	6.4
≥42	0	26	0	0.0	0.0	0.0	26	0.0	0.0	0.0
Total‡	703	34,944	753	19.7	21.5	40.8	35,647	19.7	21.5	40.8

† Total births at each gestational week served as the denominator for stillbirth and perinatal mortality rates (1), while live births at each gestational week constituted the denominator for early neonatal death rates (1). Stillbirth, early neonatal death and perinatal mortality rates (2) were calculated using fetuses at risk as the denominator (see text). All rates expressed per 1,000. ‡ All gestational ages, including those <32 weeks and those with missing gestational age.

ISSN: 1471-2393