Table 1.

Selected baseline characteristics comparing eligible and participating sons in the Study of the Environment and Reproduction, adult sons' follow-up of the CHDS

	Eligible		Provided interview			Provided interview and semen
	n = 3471a		n = 338			n = 196
Characteristic at baseline	n	%	n	%	P-valueb	n	%	P-value b
Mother's race/ethnicity
White	2275	65.6	224	66.3		122	62.2
African American	850	24.5	70	20.7		45	23.0
Hispanic	89	2.6	9	2.7		8	4.1
Asian	148	4.3	28	8.3		17	8.7
Multi-racial/Other	108	3.1	7	2.1		4	2.0
Unknown	1	–		–	0.0082		–	0.0288
Mother's age (quartiles; years)
⩽22	809	23.4	53	15.7		34	17.4
23–26	946	27.3	75	22.3		45	23.0
27–31	875	25.3	98	29.1		58	29.6
30 +	835	24.1	111	32.9		59	30.1
Unknown	6	–	1	–	<0.0001		–	0.0402
Mother's parity
Primiparous	1086	31.3	71	21.0		37	18.9
Multiparous	2385	68.7	267	79.0	<0.0001	159	81.1	0.0002
Mother's education
Less than high school	559	16.2	48	14.2		29	14.8
High school/trade school	1138	32.9	113	33.4		64	32.7
College	1764	51.0	177	52.4		103	52.6
Unknown	10	–	–	–	0.6442		–	0.8582
Mother's employment
Homemaker	1859	55.8	214	64.7		122	63.5
Professional/managerial	387	11.6	33	10.0		20	10.4
Secretarial/clerical	853	25.6	64	19.3		36	18.8
Laborer (housework/factory)	225	6.8	17	5.1		11	5.7
Other	10	0.3	3	0.9		3	1.6
Unknown	137	–	7	–	0.0075	4	–	0.0084
Mother's smoking
Never	1634	49.1	169	51.2		98	51.0
Current	1131	34.0	93	28.2		47	24.5
Past	566	17.0	68	20.6		47	24.5
Unknown	140	–	8	–	0.0626	4	–	0.0044
Mother's coffee consumption (quartiles)
<1/2 cup per day	699	23.4	67	24.8		44	27.3
1/2–1 cup per day	680	22.8	49	18.2		28	17.4
2–3 cups per day	806	27.0	69	25.6		46	28.6
4 + cups per day	798	26.8	85	31.5		43	26.7
Unknown	488	–	68	–	0.1850	35	–	0.3767
Mother's alcohol consumption (quartiles)
<1 drink per weekc	1327	44.5	131	48.5		76	47.2
1–2 drinks per week	1072	35.9	83	30.7		53	32.9
3 + drinks per week	585	19.6	56	20.7		32	19.9
Unknown	487	–	68	–	0.2296	35	–	0.7234
Offspring birth weight (quartiles; g)
⩽2940	686	19.8	64	18.9		40	20.4
2941–3276	839	24.2	76	22.5		45	23.0
3277–3584	884	25.5	89	26.3		53	27.0
⩾3585	1062	30.6	109	32.3	0.8410	58	29.6	0.9417
Offspring gestational age (quartiles; weeks)
⩽38	772	22.4	71	21.2		53	27.0
39	779	22.6	81	24.2		40	20.4
40	858	24.9	76	22.7		43	21.9
⩾41	1031	30.0	107	31.9		60	30.6
Unknown	31	–	3	–	0.6711		–	0.4168

CHDS, Child Health and Development Studies.

Bold values are significant at P < 0.05.

Quartiles are based on the distribution of variables among all CHDS births. For birth weight and gestational age, quartile cutpoints were based on the distribution among liveborn CHDS births.

^aEligible sample size is equivalent to total eligible (n = 3809) minus participants (n = 338).

^bBased on chi-square test of distribution. P-values for participants are given for the comparison of distributions between the eligible sample (n = 3471) and the participant sample (n = 338), and the comparison between the eligible sample and the sample that also provided semen (n = 196).

^cOwing to clumping of data, quartiles 1 and 2 are combined at this cutpoint.