Table 1.
Maternal characteristics of the study population: predominantly urban, low-income, minority mother–infant dyads (n 7576) enrolled in the Boston Birth Cohort, USA, from 1998 to 2014
| Maternal characteristics | Multivitamin supplement sample | Plasma folate sub-sample | ||||||
|---|---|---|---|---|---|---|---|---|
| Term (n 5507; 73 %) | PTB (n 2069; 27 %) | Term (n 1593; 69 %) | PTB (n 720; 31 %) | |||||
| n | % | n | % | n | % | n | % | |
| Race/ethnicity | ||||||||
| Non-Hispanic Black* | 2764 | 50·2 | 1083 | 52·3 | 1133 | 71·1 | 555 | 77·1 |
| Non-Hispanic White | 645 | 11·7 | 275 | 13·3 | 65 | 4·1 | 27 | 3·8 |
| Hispanic | 1614 | 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 (years) | ||||||||
| <20 | 608 | 11·0 | 195 | 9·4 | 159 | 10·0 | 67 | 9·3 |
| 20–34 | 4053 | 73·6 | 1446 | 69·9 | 1171 | 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 | ||||||||
| Foreign born | 3403 | 61·8 | 1118 | 54·0 | 970 | 60·9 | 377 | 52·4 |
| US born | 2029 | 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 | 1680 | 30·5 | 623 | 30·1 | 434 | 27·2 | 204 | 28·3 |
| High school/GED | 1800 | 32·7 | 741 | 35·8 | 575 | 36·1 | 279 | 38·8 |
| Some/beyond college | 1970 | 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 | 2038 | 37·0 | 698 | 33·7 | 564 | 35·4 | 225 | 31·3 |
| Unmarried | 3339 | 60·6 | 1339 | 64·7 | 1019 | 64·0 | 488 | 67·8 |
| Missing | 130 | 2·4 | 32 | 1·5 | 10 | 0·6 | 7 | 1·0 |
| Receipt of public assistance† | ||||||||
| No | 856 | 15·5 | 354 | 17·1 | 208 | 13·1 | 112 | 15·6 |
| Yes | 4651 | 84·5 | 1715 | 82·9 | 1385 | 86·9 | 608 | 84·4 |
| Parity | ||||||||
| Multiparous | 3119 | 56·6 | 1180 | 57·0 | 933 | 58·6 | 425 | 59·0 |
| Nulliparous | 2374 | 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 | 4449 | 80·8 | 1534 | 74·1 | 1321 | 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 | 4858 | 88·2 | 1782 | 86·1 | 1431 | 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 |
| Stress‡ | ||||||||
| No | 4404 | 80·0 | 1544 | 74·6 | 1270 | 79·7 | 535 | 74·3 |
| Yes | 1078 | 19·6 | 516 | 24·9 | 317 | 19·9 | 183 | 25·4 |
| Missing | 25 | 0·5 | 9 | 0·4 | 6 | 0·4 | 2 | 0·3 |
| BMI category§ | ||||||||
| Underweight | 227 | 4·1 | 97 | 4·7 | 62 | 3·9 | 27 | 3·8 |
| Normal | 2494 | 45·3 | 859 | 41·5 | 701 | 44·0 | 269 | 37·4 |
| Overweight/obese | 2367 | 43·0 | 973 | 47·0 | 745 | 46·8 | 386 | 53·6 |
| Missing | 419 | 7·6 | 140 | 6·8 | 85 | 5·3 | 38 | 5·3 |
| Pre-eclampsia disorders║ | ||||||||
| No | 5047 | 91·6 | 1582 | 76·5 | 1483 | 93·1 | 534 | 74·2 |
| Yes | 460 | 8·4 | 487 | 23·5 | 110 | 6·9 | 186 | 25·8 |
| Intra-uterine infection/inflammation¶ | ||||||||
| No | 4371 | 79·4 | 1557 | 75·3 | 1361 | 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 | 5162 | 93·7 | 1850 | 89·4 | 1498 | 94·0 | 632 | 87·8 |
| Gestational | 220 | 4·0 | 124 | 6·0 | 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 | ||||||||
| None | 5137 | 93·3 | 1940 | 93·8 | 1504 | 94·4 | 671 | 93·2 |
| Any | 370 | 6·7 | 129 | 6·2 | 89 | 5·6 | 49 | 6·8 |
PTB, preterm birth; GED, General Equivalency Diploma.
Non-Hispanic Black includes Black, African American, Haitian, Cape Verdian.
Public assistance is defined as receipt of any of the following: WIC (Special Supplemental Nutrition Program for Women, Infants, and Children), food stamps, AFDC (Aid to Families with Dependent Children, now known as TANF (Temporary Aid to Needy Families)), housing assistance or fuel assistance.
Mother’s self-report of life or pregnancy being very stressful.
Underweight, BMI <18·5 kg/m2; normal weight, BMI = 18·5–24·9 kg/m2; overweight/obesity, BMI≥25·0 kg/m2.
Pre-eclampsia disorders are defined as the presence of pre-eclampsia, gestational hypertension and HELLP (haemolysis, elevated liver enzymes and low platelets) syndrome.
Intra-uterine infection/inflammation is defined as the presence of maternal fever or placenta pathology findings of villitis, deciduitis, chorioamnionitis, chorionitis, subchorionitis, funisitis and free membranitis.