. Author manuscript; available in PMC: 2018 Jul 6.

Published in final edited form as: Birth Defects Res A Clin Mol Teratol. 2009 Jul;85(7):621–628. doi: 10.1002/bdra.20573

Table 1.

Selected Characteristics of Controls (n = 5875) by Exposure Status, National Birth Defects Prevention Study, 1997–2004

	Nonexposed		Thyroid Disease

	n = 5764		n = 111

	n^a	%	n^a	%
Maternal age (years)
12–19	642	11.1	2	1.8
20–34	4334	75.2	84	75.7
35+	788	13.7	25	22.5
Race/ethnicity
White non-Hispanic	3424	59.6	87	79.1
Black non-Hispanic	668	11.6	1	0.9
Hispanic	1302	22.7	14	12.7
Other	349	6.1	8	7.3
Education (years)
0–11	977	17.1	5	4.6
12	1446	25.3	16	14.7
12+	3298	57.6	88	80.7
Parity
0	2319	40.3	35	31.5
1 or more	3440	59.7	76	68.5
Prepregnancy BMI
<30	4666	84.4	88	79.3
30+ (obese)	861	15.6	23	20.7
Gestational diabetes
No	5417	94.0	101	91.0
Yes	347	6.0	10	9.0
Smoking^b
No	4640	80.9	96	87.3
Yes	1097	19.1	14	12.7
Alcohol (maximum number of drinks per occasion)^b
0	3599	63.3	66	60.6
1–3	1397	24.6	27	24.8
4+	692	12.2	16	14.7
Folic acid supplement use^c
Yes, early	2972	52.6	79	73.8
Yes, later	1954	34.6	23	21.5
No	720	12.8	5	4.7

Numbers vary because of missing values.

During the period from 1 month prepregnancy through the 3rd month of pregnancy.

Early is defined as any use one month prepregnancy through pregnancy month one. Later is defined as any use starting in pregnancy month two or three. No is defined as none or use starting after 3rd month of pregnancy.

BMI, body mass index (weight in kg/height in m²).