Table 4.

Number of twin individuals, mean and standard deviation of birth weight (kg) and BMI (kg/m²) by birth order, age and sex in monozygotic twins

		Men					Women
	Birth order	N	Mean	p valuea	SD	p valueb	N	Mean	p valuea	SD	p valueb
Age 1	1	2843	17.21	<0.001	1.41	0.798	2994	16.84	<0.001	1.42	0.755
	2	2838	17.11		1.42		2991	16.74		1.42
Age 2	1	2310	16.62	<0.001	1.40	0.921	2339	16.17	<0.001	1.38	0.915
	2	2293	16.51		1.39		2323	16.04		1.38
Age 3	1	2830	16.02	<0.001	1.41	0.276	3140	15.68	<0.001	1.50	0.217
	2	2834	15.88		1.39		3125	15.58		1.47
Age 4	1	1600	15.90	0.023	1.78	0.506	1594	15.71	0.001	2.01	0.355
	2	1588	15.84		1.81		1595	15.59		1.98
Age 5	1	1272	15.34	<0.001	1.54	0.671	1341	15.13	<0.001	1.64	0.360
	2	1266	15.20		1.51		1328	15.01		1.64
Age 6	1	528	15.54	0.265	1.77	0.735	427	15.25	0.084	1.76	0.735
	2	512	15.48		1.77		421	15.14		1.74
Age 7	1	2345	15.40	0.002	1.69	0.419	2540	15.44	<0.001	1.93	0.314
	2	2330	15.31		1.71		2536	15.31		1.93
Age 8	1	1057	15.64	0.026	1.72	0.331	1020	15.65	<0.001	1.97	0.240
	2	1042	15.54		1.67		1021	15.50		1.93
Age 9	1	1042	16.29	0.057	2.10	0.318	1005	16.33	0.152	2.38	0.556
	2	997	16.23		2.17		986	16.22		2.39
Age 10	1	1988	16.64	0.005	2.30	0.042	2088	16.67	<0.001	2.45	0.502
	2	1924	16.54		2.17		2048	16.56		2.40
Age 11	1	1530	17.32	<0.001	2.56	0.004	1588	17.37	0.035	2.72	0.374
	2	1470	17.10		2.44		1530	17.30		2.80
Age 12	1	2032	17.87	<0.001	2.72	0.197	2127	17.92	<0.001	2.74	0.999
	2	1955	17.72		2.67		2053	17.77		2.71
Age 13	1	692	18.45	0.092	2.89	0.051	642	18.94	0.094	3.19	0.383
	2	620	18.30		2.79		591	18.82		3.27
Age 14	1	1328	19.28	0.132	2.86	0.422	1497	19.67	0.007	3.02	0.956
	2	1280	19.23		2.82		1468	19.59		3.01
Age 15	1	658	19.64	0.194	2.92	0.416	639	19.95	0.168	3.20	0.503
	2	639	19.59		2.93		606	19.80		3.15
Age 16	1	1074	20.68	0.138	2.99	0.106	1311	20.64	0.098	2.98	0.172
	2	1028	20.55		2.87		1257	20.57		2.95
Age 17	1	1100	20.94	0.387	2.72	0.850	1411	20.73	0.112	2.87	0.982
	2	1074	20.88		2.68		1388	20.60		2.85
Age 18	1	1253	21.32	0.479	2.57	0.098	826	21.00	0.286	2.82	0.170
	2	1253	21.33		2.49		812	20.81		2.74
Age 19	1	639	21.66	0.513	2.51	0.900	717	21.00	0.892	2.76	0.300
	2	607	21.59		2.59		702	20.95		2.83
Age 20–29	1	2890	23.09	0.010	2.96	0.554	3488	21.85	0.010	3.69	0.340
	2	2878	22.94		2.97		3478	21.73		3.57
Age 30–39	1	2305	24.65	0.461	3.39	0.215	3378	22.86	0.712	4.03	0.309
	2	2290	24.52		3.30		3349	22.85		4.07
Age 40–49	1	1420	25.44	0.137	3.59	0.042	1886	23.75	0.676	4.20	0.428
	2	1355	25.25		3.33		1844	23.77		4.33
Age 50–59	1	1038	25.43	0.668	3.21	0.523	1601	24.65	0.384	4.30	0.368
	2	1029	25.56		3.18		1609	24.55		4.13
Age 60–69	1	506	25.59	0.852	3.20	0.264	880	25.24	0.168	4.26	0.312
	2	494	25.73		3.28		878	25.02		4.17
Age 70–79	1	126	24.74	0.925	3.20	0.532	273	24.95	0.675	4.30	0.213
	2	117	24.90		3.27		268	24.58		3.71

p value^a: p value for equality of means, p value^b: p value for equality of variances, SD: standard deviation.