A parsimonious explanation for intersecting perinatal mortality curves: understanding the effects of race and of maternal smoking

Table 1 Numbers and Rates of Live Births, Stillbirths and Neonatal Deaths among Singletons Births, Whites, United States, 1997.

Gestational age	Stillbirths	Live births	Neonatal deaths	Stillbirth rate (1)*	Perinatal mortality rate (1)*	Neonatal mortality rate (1)*	Fetuses-at-risk	Stillbirth rate (2)*	Perinatal mortality rate (2)*	Neonatal mortality rate (2)*
32	464	12,378	188	36.1	48.0	15.2	2,932,342	0.16	0.21	0.06
33	515	18,462	193	27.1	34.8	10.5	2,919,500	0.18	0.23	0.07
34	549	32,600	269	16.6	23.1	8.3	2,900,523	0.19	0.26	0.09
35	621	56,901	317	10.8	15.1	5.6	2,867,374	0.22	0.30	0.11
36	695	105,595	340	6.5	8.8	3.2	2,809,852	0.25	0.33	0.12
37	750	215,174	437	3.5	4.9	2.0	2,703,562	0.28	0.39	0.16
38	847	457,012	520	1.8	2.5	1.1	2,487,638	0.34	0.46	0.21
39	796	715,694	628	1.1	1.6	0.9	2,029,779	0.39	0.58	0.31
40	690	691,945	551	1.0	1.4	0.8	1,313,289	0.53	0.76	0.42
41	379	377,523	311	1.0	1.5	0.8	620,654	0.61	0.90	0.50
≥42†	351	242,401	286	1.4	2.2	1.2	242,752	1.45	2.16	1.18
Total ‡	12,987	2,986,954	7,520	4.3	6.1	2.5	2,999,941	4.33	6.12	2.51

* 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 neonatal mortality rates (1). Stillbirth, perinatal (stillbirths plus early neonatal deaths) and neonatal mortality rates (2) were calculated using fetuses-at-risk as the denominator (see text). All rates are expressed per 1,000. † This period of risk exceeds 1 week and partly explains the large increase in the perinatal mortality (2). ‡All gestational ages, including those <32 weeks and those with missing gestational age.

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