Table 1:

Maternal Characteristics of Study Population (N=7, 576)

Maternal Characteristics	Multivitamin Supplement sample				Plasma folate subsample
	Term		PTB		Term		PTB
	N	%	N	%	N	%	N	%
	5,507	73	2,069	27	1,593	69	720	31
Race/ethnicity
Non-Hispanic Blacka	2,764	50.2	1,083	52.3	1,133	71.1	555	77.1
Non-Hispanic White	645	11.7	275	13.3	65	4.1	27	3.8
Hispanic	1,614	29.3	536	25.9	323	20.3	115	16.0
Other	451	8.2	163	7.9	72	4.5	23	3.2
Missing	33	0.6	12	0.6	0	0.0	0	0.0
Age in years
<20	608	11.0	195	9.4	159	10.0	67	9.3
20–34	4,053	73.6	1,446	69.9	1,171	73.5	494	68.6
35+	813	14.8	416	20.1	263	16.5	159	22.1
Missing	33	0.6	12	0.6	0	0.0	0	0.0
Nativity (US born)
Foreign born	3,403	61.8	1,118	54.0	970	60.9	377	52.4
US born	2,029	36.8	935	45.2	596	37.4	338	46.9
Missing	75	1.4	16	0.8	27	1.7	5	0.7
Education
Less than high school	1,680	30.5	623	30.1	434	27.2	204	28.3
High School/GED	1,800	32.7	741	35.8	575	36.1	279	38.8
Some/beyond College	1,970	35.8	684	33.1	578	36.3	234	32.5
Missing	57	1.0	21	1.0	6	0.4	3	0.4
Marital Status
Married	2,038	37.0	698	33.7	564	35.4	225	31.3
Unmarried	3,339	60.6	1,339	64.7	1,019	64.0	488	67.8
Missing	130	2.4	32	1.5	10	0.6	7	1.0
Receipt of public assistance b
No	856	15.5	354	17.1	208	13.1	112	15.6
Yes	4,651	84.5	1,715	82.9	1,385	86.9	608	84.4
Parity
Multiparous	3,119	56.6	1,180	57.0	933	58.6	425	59.0
Nulliparous	2,374	43.1	885	42.8	657	41.2	294	40.8
Missing	14	0.3	4	0.2	3	0.2	1	0.1
Cigarette smoking
Never	4,449	80.8	1,534	74.1	1,321	82.9	545	75.7
Ever	376	6.8	175	8.5	114	7.2	73	10.1
Continued in pregnancy	611	11.1	336	16.2	145	9.1	99	13.8
Missing	17	1.3	24	1.2	13	0.8	3	0.4
Alcohol consumption
No	4,858	88.2	1,782	86.1	1,431	89.8	644	89.4
Yes	474	8.6	218	10.5	124	7.8	67	9.3
Missing	175	3.2	69	3.3	38	2.4	9	1.3
Stressc
No	4,404	80	1,544	74.6	1,270	79.7	535	74.3
Yes	1,078	19.6	516	24.9	317	19.9	183	25.4
Missing	25	0.5	9	0.4	6	0.4	2	0.3
Body Mass Index categories
Underweight	227	4.1	97	4.7	62	3.9	27	3.8
Normal	2,494	45.3	859	41.5	701	44.0	269	37.4
Overweight/obese	2,367	43	973	47	745	46.8	386	53.6
Missing	419	7.6	140	6.8	85	5.3	38	5.3
Preeclampsia disorders d
No	5,047	91.6	1,582	76.5	1,483	93.1	534	74.2
Yes	460	8.4	487	23.5	110	6.9	186	25.8
Intrauterine infection/inflammation
No	4,371	79.4	1,557	75.3	1,361	85.4	560	77.8
Yes	690	12.5	432	20.9	169	10.6	151	21.0
Missing	446	8.1	80	3.9	63	4.0	9	1.3
Diabetes Mellitus
None	5,162	93.7	1,850	89.4	1,498	94.0	632	87.8
Gestational	220	4.0	124	6	53	3.3	49	6.8
Pre-gestational	75	1.4	79	3.8	31	1.9	34	4.7
Missing	50	0.9	16	0.8	11	0.7	5	0.7
Multivitamin supplement intake
Preconception	9
None	5,137	93.3	1,940	93.8	1,504	94.4	671	93.2
Any	370	6.7	129	6.2	89	5.6	49	6.8

Abbreviation: GED-General Equivalency Diploma; N-number; PTB-preterm birth; SD-standard deviation; US-United States; WHO-World Health Organization.

^aNon-Hispanic Black includes Black, African American, Haitian, Cape Verdian.

^bPublic assistance is defined as receipt of any of the following: WIC (Women Infants and Children), food stamps, AFDC (Aid to families with dependent children), housing assistance or fuel assistance.

^cMother’s self-report of life or pregnancy being very stressful.

^dPreeclampsia disorders are defined as the presence of preeclampsia, gestational hypertension and hemolysis, elevated liver enzymes, and low platelet (HELLP) syndrome