Table 1. Characteristics of the Study Population in Project Viva.
| Characteristic | No. (%) | P valuea | ||||
|---|---|---|---|---|---|---|
| Total population (N = 1400) | First quartile (n = 350) | Second quartile (n = 350) | Third quartile (n = 350) | Fourth quartile (n = 350) | ||
| Dietary folate intake, range, μg/d | 128.7-3497.2 | 128.7-660.4 | 660.4-936.2 | 936.2-1187.3 | 1187.3-3497.2 | NA |
| Maternal age, mean (SD), y | 32.21 (4.89) | 30.67 (5.85) | 32.20 (4.93) | 32.82 (4.30) | 33.15 (3.89) | <.001 |
| Prepregnancy BMI, mean (SD) | 24.78 (5.39) | 25.99 (6.31) | 24.66 (5.51) | 24.31 (4.64) | 24.16 (4.74) | <.001 |
| AHEI-P score, mean (SD)b | 60.46 (10.25) | 55.67 (9.74) | 58.53 (9.38) | 63.09 (9.96) | 64.56 (9.39) | <.001 |
| Maternal race and ethnicityc | ||||||
| Asian | 68 (4.9) | 22 (6.3) | 16 (4.6) | 16 (4.6) | 14 (4.0) | <.001 |
| Black | 167 (11.9) | 83 (23.7) | 40 (11.4) | 23 (6.6) | 21 (6.0) | |
| Hispanic | 87 (6.2) | 38 (10.9) | 17 (4.9) | 22 (6.3) | 10 (2.9) | |
| White | 1025 (73.2) | 183 (52.3) | 265 (75.7) | 285 (81.4) | 292 (83.4) | |
| Other | 53 (3.8) | 24 (6.9) | 12 (3.4) | 4 (1.1) | 13 (3.7) | |
| Maternal education ≥ college degree | 968 (69.1) | 173 (49.4) | 246 (70.3) | 261 (74.6) | 288 (82.3) | <.001 |
| Paternal education ≥ college degreed | 888 (63.4) | 144 (41.1) | 213 (60.9) | 257 (73.4) | 274 (78.3) | <.001 |
| Annual household income >$70 000e | 820 (58.6) | 149 (42.6) | 201 (57.4) | 222 (63.4) | 248 (70.9) | <.001 |
| Prenatal smokingf | ||||||
| Never | 932 (66.6) | 228 (65.1) | 225 (64.3) | 233 (66.6) | 246 (70.3) | <.001 |
| Former | 296 (21.1) | 53 (15.1) | 82 (23.4) | 81 (23.1) | 80 (22.9) | |
| Early pregnancy | 168 (12.0) | 68 (19.4) | 43 (12.3) | 35 (10.0) | 22 (6.3) | |
| Nulliparous | 696 (49.7) | 133 (38.0) | 165 (47.1) | 208 (59.4) | 190 (54.3) | <.001 |
| Planned pregnancyg | 879 (62.8) | 124 (35.4) | 215 (61.4) | 255 (72.9) | 285 (81.4) | <.001 |
| Infertility | 306 (21.9) | 40 (11.4) | 73 (20.9) | 82 (23.4) | 111 (31.7) | <.001 |
| Periconception folic acid supplement useh | 957 (68.4) | 79 (22.6) | 230 (65.7) | 305 (87.1) | 343 (98.0) | <.001 |
| Ever breastfeedingi | 516 (36.9) | 147 (42.0) | 127 (36.3) | 112 (32.0) | 130 (37.1) | <.001 |
| Female infant | 685 (48.9) | 175 (50.0) | 170 (48.6) | 166 (47.4) | 174 (49.7) | .90 |
| Gestational age, mean (SD), wk | 39.49 (1.86) | 39.30 (2.14) | 39.56 (1.76) | 39.72 (1.50) | 39.36 (1.95) | .01 |
| Birth weight, mean (SD), g | 3486.7 (572.8) | 3427.6 (637.6) | 3503.6 (571.3) | 3522.4 (493.6) | 3493.1 (577.6) | .14 |
| Birth weight z score, mean (SD)j | 0.21 (0.95) | 0.14 (1.03) | 0.22 (0.96) | 0.20 (0.90) | 0.27 (0.90) | .38 |
| Preterm birth | 99 (7.1) | 33 (9.4) | 22 (6.3) | 15 (4.3) | 29 (8.3) | .04 |
| Low birth weight | 64 (4.6) | 21 (6.0) | 16 (4.6) | 9 (2.6) | 18 (5.1) | .16 |
Abbreviations: AHEI-P, Alternative Healthy Eating Index in Pregnancy; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); NA, not applicable.
P values obtained from χ2 tests for categorical variables and t tests for continuous variables across folate groups.
Higher AHEI-P score indicates better diet quality.
Race and ethnicity was self-reported in the questionnaire. American Indian or Alaska Native and other were collapsed into a single category to balance sample size.
Missingness: 97 (6.93%) for paternal educational level.
Missingness: 96 (6.86%) for household income.
Missingness: 4 (0.29%) for prenatal smoking.
Missingness: 27 (1.93%) for planned pregnancy.
Periconception folic acid supplement use was defined by any use of prenatal vitamin or folic acid supplement during gestational weeks 0 to 4. Missingness: 1.
Missingness: 78 (5.57%) for ever breastfeeding.
Birth weight z score standardized by gestational age and sex, using a US national reference.