Table 2.

Point Estimates of the Low and High Optimal Birth Weight and Percentiles of the Birth Weight Distribution at 36–40 Weeks’ Gestational Age Among Female and Male Twin Livebirths, United States, 1995–2002

Gestational Age, weeks	Low Optimal Weight, g		High Optimal Weight, g		Birth Weight, g, by Percentile
	Estimate	95% Confidence Interval	Estimate	95% Confidence Interval	3	10	90	97
Females
36	2,106	2,069, 2,143	4,248	3,906, 4,590	1,814	2,040	2,920	3,147
37	2,331	2,293, 2,369	4,151	3,884, 4,418	1,956	2,183	3,085	3,323
38	2,592	2,555, 2,629	4,193	3,897, 4,489	2,070	2,296	3,232	3,470
39	2,724	2,689, 2,759	4,327	4,029, 4,625	2,126	2,353	3,290	3,544
40	2,822	2,788, 2,856	4,230	3,911, 4,549	2,126	2,325	3,345	3,629
Males
36	2,139	2,101, 2,177	4,445	4,098, 4,792	1,899	2,126	3,033	3,278
37	2,365	2,327, 2,403	4,353	4,093, 4,613	2,041	2,268	3,204	3,459
38	2,625	2,587, 2,663	4,392	4,102, 4,682	2,135	2,381	3,350	3,615
39	2,756	2,718, 2,794	4,529	4,237, 4,821	2,183	2,448	3,459	3,725
40	2,854	2,820, 2,888	4,427	4,119, 4,735	2,211	2,466	3,487	3,799