Table 1.

Sample Characteristics.

	Cohort 1 (Singletons)			Cohort 2 (Twins)
	N	Mean	SD	N	Mean	SD	P-Value
Birthweight (grams)	252	3458.3	414.32	182	2616.11	351.65	1.18E-75
Gestational age at birth (days)	252	278.1	7.21	182	257.81	7.96	4.32E-90
Mother’s education (years)*	251	16.28	2.97	182	15.17	3.74	1.05E-03
Father’s education (years)*	248	15.95	3.37	176	14.98	3.99	0.01
Total household income ($)*	236	82444.53	105282.9	171	75901.16	60603.9	0.43
Age at scan, neonate (days)	181	21.13	9.35	157	33.15	15.76	4.54E-15
Age at scan, 1 year (days)	111	379.87	21.44	109	400.28	28.07	6.77E-09
Age at scan, 2 year (days)	70	738.84	19.7	80	764.86	28.22	7.36E-10
Age at scan, 4 year (days)	92	1480.05	34.4	56	1505.96	69.55	0.01
Age at scan, 6 year (days)	90	2210.52	34.04	56	2228	52.6	0.03
	N	Allegra	Trio	N	Allegra	Trio
Scanner, Neonate	181	151	30	157	123	34	0.29
Scanner, Year 1	111	87	24	109	90	19	0.54
Scanner, Year 2	70	56	14	80	51	29	0.04
Scanner, Year 4	92	44	48	56	9	47	1.91E-04
Scanner, Year 6	90	32	58	56	7	49	4.11E-03
	N	Male	Female	N	Male	Female
Sex	252	121	131	182	99	83	0.22
	White	Black	Other	White	Black	Other
Mother’s Ethnicity (N)	207	39	6	143	33	6	0.63
Mother’s Ethnicity (%)	82.14	15.48	2.38	78.57	18.13	3.3
Father’s Ethnicity (N)	197	45	8	133	37	9	0.46
Father’s Ethnicity (%)	78.8	18	3.2	74.3	20.67	5.03
	N	Yes	No	N	Yes	No
Mother smoking during pregnancy	252	9	243	182	11	171	0.33

^*(indicates assessed at time of enrollment).