Table 1.

Detailed demographic information of subjects included in this study

	n	Sex (males/females)	Age (postnatal days)
1 month	178	129/85	37 ± 18
Singletons	36	17/19	22 ± 9
Dizygotic twins	80	46/34	36 ± 15
Monozygotic twins	62	30/32	46 ± 16
12 months	132	87/59	397 ± 26
Singletons	46	23/23	378 ± 17
Dizygotic twins	50	31/19	402 ± 28
Monozygotic twins	36	16/20	410 ± 17
24 months	100	58/41	765 ± 32
Singletons	26	17/9	741 ± 25
Dizygotic twins	38	25/13	779 ± 35
Monozygotic twins	36	16/20	766 ± 23