A cohort study of in utero polychlorinated biphenyl (PCB) exposures in relation to secondary sex ratio

Table 2 Sample characteristics, Child Health and Development Study, 1964–67

	Final stratified random sample (n = 399)		Cases meeting study criteria (n = 1291)		Cases followed up at 5 years (n = 3412)		CHDS study population (n = 20754)
Characteristics*	N	%†	N	%	N	%	N	%
Maternal age
< 20	28	7	68	5	230	7	1731	9
20–29	242	61	786	61	2099	62	12028	59
≥ 30	128	32	436	34	1068	31	6724	33
Parity
0	122	31	400	31	1077	32	6289	31
1–2	177	44	605	47	1572	47	9270	45
≥ 3	100	25	286	22	717	21	5031	24
Race/ethnicity
White	194	49	648	50	1970	58	1347	66
African-American	165	41	496	38	1041	31	4936	24
Hispanic	7	2	40	3	130	4	678	3
Asian	20	5	70	5	150	4	783	4
Multi-racial/other	13	3	37	3	108	3	597	3
Mother's education
Not High School graduate	76	19	208	16	500	17	3341	19
High School graduate	160	40	484	38	1118	37	6661	38
Some college	163	41	599	46	1378	46	7549	43
Father's education
Not High School graduate	74	19	211	20	496	17	2997	18
High School graduate	111	29	339	32	789	27	4607	28
Some college	122	32	431	41	979	34	4329	26
College grad/RN	76	20	286	27	643	22	4681	28
Sex of infant
Female	213	53.4	658	51.0	1722	50.5	9451	48.8
Male	186	46.6	633	49.0	1690	49.5	9927	51.2

ISSN: 1476-069X