Table 4. Birth weight, length, chest circumference, and head circumference of twins by gestational age.

	gestational age (week)	male						female
		n	mean	SD	percentiles			n	mean	SD	percentiles
					10th	50th	90th				10th	50th	90th
weight (kg) primipara	27-32	20	1.694	0.163	1.342	1.734	2.018	23	1.574	0.236	1.402	1.853	2.009
	33	15	1.885	0.250	1.456	1.826	2.190	11	1.838	0.307	1.537	1.901	2.099
	34	19	1.872	0.273	1.585	1.954	2.365	19	2.109	0.223	1.659	1.986	2.235
	35	46	2.080	0.326	1.722	2.102	2.537	59	2.046	0.298	1.769	2.097	2.401
	36	48	2.314	0.280	1.861	2.259	2.704	32	2.152	0.240	1.869	2.222	2.580
	37	58	2.466	0.347	1.994	2.409	2.860	84	2.422	0.307	1.959	2.352	2.756
	38	117	2.544	0.323	2.113	2.539	3.002	122	2.473	0.363	2.039	2.475	2.911
	39	87	2.673	0.408	2.212	2.635	3.126	119	2.583	0.419	2.110	2.581	3.028
	40	62	2.630	0.389	2.284	2.684	3.226	72	2.681	0.358	2.173	2.659	3.091
	41	32	2.770	0.493	2.321	2.671	3.300	16	2.647	0.283	2.228	2.697	3.083
weight (kg) multipara	27-32	9	1.672	0.212	1.489	1.781	2.094	7	1.619	0.181	1.653	1.891	2.294
	33	13	1.932	0.229	1.606	1.941	2.258	5	2.129	0.198	1.662	1.948	2.377
	34	21	2.060	0.366	1.731	2.108	2.442	15	2.108	0.262	1.713	2.042	2.489
	35	41	2.313	0.296	1.861	2.275	2.636	69	2.184	0.380	1.794	2.162	2.621
	36	44	2.397	0.359	1.989	2.435	2.829	32	2.273	0.412	1.896	2.296	2.765
	37	93	2.525	0.296	2.112	2.582	3.009	81	2.517	0.287	2.008	2.433	2.912
	38	106	2.699	0.420	2.224	2.709	3.167	133	2.576	0.319	2.121	2.562	3.055
	39	70	2.837	0.370	2.320	2.810	3.291	110	2.664	0.340	2.225	2.671	3.184
	40	58	2.882	0.404	2.397	2.877	3.371	64	2.757	0.376	2.308	2.749	3.291
	41	11	2.880	0.324	2.448	2.905	3.396	15	3.003	0.516	2.361	2.784	3.368
length (cm)	27-32	14	40.8	1.9	38.0	40.5	43.0	18	41.4	2.3	37.5	41.3	45.0
	33	22	43.3	2.5	39.9	43.3	46.1	16	42.8	2.0	40.5	43.0	45.0
	34	33	43.9	2.2	41.1	44.4	47.0	33	44.1	1.6	41.0	44.0	46.1
	35	80	45.3	2.3	42.3	45.3	47.9	114	44.7	2.3	41.7	44.8	47.2
	36	87	46.1	2.1	43.5	46.2	48.7	57	44.8	2.4	42.5	45.6	48.1
	37	142	47.0	1.7	44.5	47.0	49.4	160	46.6	2.0	43.3	46.4	48.8
	38	219	47.7	2.1	45.3	47.7	50.0	250	46.7	2.3	44.1	47.0	49.5
	39	150	48.4	1.8	45.8	48.2	50.4	226	47.4	2.1	44.6	47.6	49.9
	40	119	48.0	2.3	45.9	48.6	50.6	129	48.0	2.0	45.0	48.1	50.2
	41	40	48.3	2.3	45.5	48.7	50.5	31	48.2	2.3	45.1	48.4	50.4
chest circumference (cm)	27-32	10	25.2	1.7	23.3	25.1	27.5	12	25.3	1.5	23.5	25.3	27.0
	33	20	26.6	1.6	24.2	26.7	28.8	12	26.9	1.8	24.1	26.9	28.8
	34	30	27.3	1.7	25.2	27.5	29.9	28	27.2	1.3	24.9	27.5	29.5
	35	75	28.2	2.0	26.0	28.4	30.7	102	27.9	2.3	25.6	28.1	30.3
	36	83	29.4	1.8	26.7	29.2	31.4	57	28.8	2.2	26.4	28.8	31.1
	37	132	29.7	1.8	27.3	29.9	31.9	148	29.7	1.9	27.0	29.4	31.8
	38	203	30.1	2.1	27.8	30.4	32.4	233	30.0	1.9	27.6	30.0	32.5
	39	143	30.9	1.8	28.2	30.8	32.9	213	30.4	2.0	28.1	30.6	33.0
	40	106	30.7	2.0	28.5	31.1	33.4	128	30.8	1.8	28.5	31.0	33.3
	41	34	31.3	2.2	28.7	31.1	34.1	28	31.3	1.8	28.7	31.4	33.3
head circumference (cm)	27-32	10	28.7	1.2	27.0	28.7	30.3	12	29.1	1.4	27.5	28.8	31.0
	33	20	30.6	1.3	28.7	30.9	32.2	12	30.4	1.1	29.2	30.6	31.7
	34	30	30.6	1.5	29.1	31.1	32.7	28	30.9	1.2	28.8	30.8	32.5
	35	76	31.4	1.6	29.6	31.5	33.1	103	30.9	1.5	29.0	31.1	33.0
	36	84	32.0	1.5	30.2	32.0	33.6	57	31.4	2.1	29.4	31.5	33.4
	37	131	32.5	1.6	30.7	32.5	34.0	148	32.0	1.3	30.0	32.0	33.6
	38	203	32.6	1.5	31.2	33.0	34.4	232	32.3	1.4	30.6	32.5	33.8
	39	143	33.1	1.4	31.5	33.3	34.7	215	32.5	1.4	31.0	32.8	34.1
	40	106	33.2	1.5	31.6	33.4	34.9	127	32.7	1.4	31.0	33.0	34.5
	41	34	33.3	1.5	31.4	33.3	35.1	28	32.8	1.8	30.5	33.0	35.0

SD: standard deviation