Customized birth weight for gestational age standards: Perinatal mortality patterns are consistent with separate standards for males and females but not for blacks and whites

Table 3 Gestational Age-Specific Rates of Fetal Growth Restriction Based on a Sex-Specific Standard [38] and Differences in Growth Restriction, Stillbirth and Early Neonatal Mortality Among Males and Females, Singleton Births, United States, 1997 and 1998.

Gestational age	Fetal growth restriction					Stillbirth rate ratio(males vs females)	Early neonatal mortality rate ratio(males vs females)
	Males		Females		Rate ratio (males vs females)
	Number	Rate †	Number	Rate †
28	631	0.2	502	0.1	1.20	1.01	1.36
29	764	0.2	660	0.2	1.10	1.04	1.33
30	1,165	0.3	923	0.3	1.20	1.10	1.23
31	1,539	0.4	1,369	0.4	1.07	1.10	1.15
32	2,141	0.6	1,866	0.5	1.09	1.22	1.02
33	3,294	0.9	2,946	0.9	1.07	1.15	1.08
34	5,691	1.6	5,098	1.5	1.07	1.13	1.29
35	8,934	2.5	7,922	2.3	1.08	1.10	1.38
36	15,813	4.6	13,910	4.2	1.09	1.13	1.19
37	30,029	9.1	25,180	7.9	1.15	1.19	1.13
38	55,401	18.5	49,599	17.1	1.09	1.07	1.27
39	84,257	35.7	79,440	33.9	1.05	1.04	1.28
40	75,983	52.8	74,504	51.1	1.03	0.98	1.16
41	36,956	62.6	34,214	56.5	1.11	0.95	1.10
≥42	14,679	100.5	14,551	96.7	1.04	1.05	1.19
Total‡	337,277	91.6	312,684	89.3	1.03	1.08	1.27

† Gestational age-specific growth restriction rates (based on a sex-specific standard [38]) were calculated by dividing the number of small-for-gestational age live births (<10^th percentile) at any gestational age by the number of fetuses at risk at that gestation. Stillbirth and early neonatal mortality rates were also calculated using fetuses at risk as the denominator.
‡ All gestational ages ≥22 weeks, except for growth restriction indices which were based on live births between 28 and 42 weeks.

ISSN: 1471-2393