Table 1.

Association of maternal and infant factors with small for gestational age (SGA) offspring among National Birth Defects Prevention Study controls, 1997–2002

Characteristic	SGA		Not SGA		p Value*
	n	%	n	%
Total	221		2582
Age (years)
<20	10	4.5	216	8.4	0.35
20–24	64	29.0	551	21.3
25–29	58	26.2	706	27.3
30–34	45	20.4	747	28.9
35+	44	19.9	362	14.0
Missing	0		0
Race/ethnicity
White non-Hispanic	141	63.8	1690	65.5	0.14
Black non-Hispanic	19	8.6	334	12.9
Hispanic	47	21.3	442	17.1
Other	14	6.3	116	4.5
Missing	0		0
Education (years)
<12	31	14.0	246	9.5	0.04
12	56	25.3	637	24.7
>12	134	60.6	1697	65.8
Missing	0		2
Parity/number of previous live births
0	82	37.1	1148	44.5	0.15
1	92	41.6	895	34.6
2+	47	21.3	539	20.9
Missing	0		0
Infant sex
Male	121	54.8	1280	49.6	0.14
Female	100	45.2	1302	50.4
Missing	0		0
Cigarette smoking†
Yes	58	26.2	522	20.2	0.03
No	163	73.8	2060	79.8
Missing	0		0
Secondhand smoking at home†
Yes	53	24.0	463	17.9	0.03
No	168	76.0	2119	82.1
Missing	0		0
Secondhand smoking at work†
Yes	52	23.5	512	19.8	0.19
No	169	76.5	2070	80.2
Missing	0		0
Alcohol drinking†
Yes	108	48.9	1209	46.8	0.56
No	113	51.1	1373	53.2
Missing	0		0
Prepregnancy body mass index
Underweight	17	8.0	126	5.0	0.01
Normal weight	136	63.8	1437	56.7
Overweight	36	16.9	588	23.2
Obese	24	11.3	385	15.2
Missing	8		46
Folate antagonist medication†
Yes	1	0.5	2	0.1	0.22‡
No	220	99.5	2580	99.9
Missing	0		0
Folic acid supplements†
Yes	204	92.3	2437	94.4	0.20
No	17	7.7	145	5.6
Missing	0		0
Household income ($)
<20 000	62	32.3	573	25.3	0.47
20 000–49 999	66	34.4	805	35.6
50 000+	64	33.3	886	39.1
Missing	29		318
Study centre
Arkansas	32	14.5	323	12.5	0.79
California	23	10.4	306	11.9
Iowa	28	12.7	364	14.1
Massachusetts	32	14.5	370	14.3
New Jersey	34	15.4	347	13.4
New York	22	9.9	297	11.5
Texas	29	13.1	267	10.3
CDC/Atlanta	21	9.5	308	11.9
Missing	0		0

^*Probability calculated with χ² test based on non-missing values.

^†Maternal exposure during the period from 1 month before conception through delivery.

^‡Fisher’s exact test.