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

Table 4 Gestational Age-Specific Birth, Growth-Restriction and Perinatal Mortality Rates, Smokers, United States, 1997.

Gestational age	Live births	SGA live births	Stillbirths	Neonatal deaths	Fetuses at risk	Birth rate	Growth-restriction rate (1)*	Growth-restriction rate (2)*	Perinatal mortality rate (1)*	Perinatal mortality rate (2)*
32	2,562	279	103	38	369,256	7.3	10.9	0.8	48.3	0.36
33	3,599	447	90	25	366,525	10.1	12.5	1.3	27.7	0.28
34	6,086	893	119	45	362,764	17.2	14.7	2.5	24.9	0.43
35	9,666	1,491	102	56	356,447	27.6	15.5	4.3	14.1	0.39
36	16,700	2,697	101	63	346,545	48.7	16.2	8.0	8.6	0.42
37	30,540	5,267	126	77	329,572	93.5	17.3	16.4	5.6	0.52
38	56,458	9,771	139	94	298,671	190.4	17.3	33.6	3.3	0.63
39	81,672	14,690	129	80	241,759	339.9	18.0	62.6	2.0	0.69
40	77,426	13,368	101	67	159,576	488.1	17.3	87.3	1.7	0.84
41	44,179	6,863	52	46	81,712	544.0	15.6	90.6	1.7	0.93
≥42†	37,017	3,161	53	49	37,289	1,000.0	18.4	100.1	2.1	2.09
Total ‡	374,605	62,319	1,810	1,332	376,415	1,000.0	17.0	169.6	7.3	7.28

* Total births and live births at each gestational week served as the denominators for perinatal mortality rates (1) and growth-restriction rates (1), respectively. Perinatal mortality and growth-restriction rates (2) were calculated using the number of fetuses at risk as the denominator (see text). Fetuses-at-risk for the growth-restriction rate calculation exclude those over 44 weeks and those with missing gestational age or birth weight. All rates are expressed per 1,000 except for growth-restriction rates (1) which are per 100. † This period of risk exceeds 1 week and partly explains the large increase in the perinatal mortality rate (2). ‡ All gestational ages, including those <32 weeks and those with missing gestational age. SGA denotes small for gestational age.

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