Table 1. Subject characteristics according to folate levels (N = 4,149).
| Folate deficient (< 7nmol/l) N = 277 | Normal folate (≥7nmol/l) N = 3,872 | |
|---|---|---|
| Maternal characteristics | ||
| Maternal age (y) | 27.5 (5.6) | 30.6 (4.8) |
| Pre-pregnancy body mass index(kg/m2) | 23.7 (21.0, 27.0) | 22.6 (20.8, 25.2) |
| Missing, n (%) | 60 (22) | 629 (16) |
| Gestational age at intake (wk) | 14.2 (12.6, 16.1) | 13.2 (12.1, 14.6) |
| Early pregnancy systolic blood pressure (mmHg) | 114 (12) | 116 (12) |
| Missing, n (%) | 3 (1) | 21 (0.5) |
| Early pregnancy diastolic blood pressure (mmHg) | 67 (10) | 68 (10) |
| Missing, n (%) | 3 (1) | 21 (0.5) |
| Late pregnancy systolic blood pressure (mmHg) | 119 (12) | 119 (12) |
| Missing, n (%) | 14 (5.1) | 120 (3.1) |
| Late pregnancy diastolic blood pressure (mmHg) | 69 (10) | 69 (9) |
| Missing, n (%) | 14 (5.1) | 120 (3.1) |
| Education level, n (%) | ||
| - No higher education | 204 (73.6) | 1,824 (47.1) |
| - Higher education | 44 (15.9) | 1,867 (48.2) |
| - Missing, n (%) | 29 (10.5) | 181 (4.7) |
| Ethnicity, n (%) | ||
| - European | 99 (35.7) | 2,555 (66.0) |
| - Non-European | 167 (60.3) | 1,264 (32.6) |
| - Missing, n (%) | 11 (4) | 53 (1.4) |
| Smoking during pregnancy, n (%) | ||
| - Never & until pregnancy was known | 154 (55.6) | 2,940 (75.9) |
| - Continued | 90 (32.5) | 545 (14.1) |
| - Missing, n (%) | 33 (11.9) | 387 (10) |
| Alcohol during pregnancy, n (%) | ||
| - Never & until pregnancy was known | 171 (61.7) | 1,939 (50.1) |
| - Continued | 59 (21.3) | 1,515 (39.1) |
| - Missing, n (%) | 47 (17) | 418 (10.8) |
| Folic acid supplements use, n (%) | ||
| - No | 166 (59.9) | 515 (13.3) |
| - Start 1st to 10 weeks | 23 (8.3) | 1,022 (26.4) |
| - Start periconceptional | 15 (5.4) | 1,492 (38.5) |
| - Missing, n (%) | 73 (26.4) | 843 (21.8) |
| Maternal calories intake (kcal) | 2,010 (599) | 2,050 (549) |
| Missing, n (%) | 76 (27.4) | 700 (18.1) |
| Vitamin supplements use, n (%) | ||
| - No | 211 (76.2) | 2,193 (56.6) |
| - Yes | 17 (6.1) | 1,114 (28.8) |
| - Missing, n (%) | 49 (17.7) | 565 (14.6) |
| Folate plasma concentrations (nmol/l) | 6.1 (5.4, 6.6) | 17.9 (11.6, 25.4) |
| Vitamin B12 serum concentrations (pmol/l) | 154.5 (115.8, 200.8) | 173.0 (131.0, 232.0) |
| Missing, n (%) | 7 (2.5) | 235 (6.1) |
| Homocysteine plasma concentrations (μmol/l) | 8.4 (7.1, 10.0) | 6.8 (6.0, 7.8) |
| Missing, n (%) | 7 (2.5) | 62 (1.6) |
| Infant characteristics | ||
| Girls, n (%) | 135 (48.7) | 1,941 (50.1) |
| Gestational age at birth (wk) | 40.1 (39.3, 40.9) | 40.1 (39.3, 41.0) |
| Birth weight (g) | 3,309 (596) | 3,447 (548) |
| Missing, n (%) | - | 4 (0.1) |
| Breastfeeding, n (%) | ||
| - No | 20 (7.2) | 231 (6.0) |
| - Yes | 178 (64.3) | 2,940 (75.9) |
| - Missing, n (%) | 79 (28.5) | 701 (18.1) |
| Cord blood folate concentrations (nmol/l) | 16.6 (13.2, 21.2) | 21.1 (16.5, 27.3) |
| Cord blood vitamin B12 concentrations (pmol/l) | 267.5 (210.3, 379.8) | 302.0 (220.0, 422.0) |
| Cord blood homocysteine concentrations (μmol/l) | 9.8 (8.4, 12.3) | 9.3 (7.4, 10.6) |
| Child characteristics at 6y visit | ||
| Age (y) | 6.1 (5.9, 6.5) | 6.0 (5.9, 6.2) |
| Height (cm) | 120.0 (6.9) | 119.3 (5.9) |
| Missing, n (%) | - | 6 (0.2) |
| Weight (kg) | 23.0 (20.8, 27.5) | 22.4 (20.4, 25.0) |
| Missing, n (%) | - | 6 (0.2) |
| Body mass index (kg/m2) | 16.1 (15.3, 18.1) | 15.8 (15.0, 16.9) |
| Missing, n (%) | - | 6 (0.2) |
| Body surface area (m2) | 0.9 (0.1) | 0.9 (0.1) |
| Missing, n (%) | - | 6 (0.2) |
| Combined kidney volume (cm3) | 122.1 (28.6) | 120.0 (23.2) |
| Creatinine (μmol/l) | 38.2 (5.2) | 37.3 (5.6) |
| Cystatin C (mg/l) | 783.1 (74.8) | 784.4 (81.8) |
| eGFRcreat ( ml/min/1.73m2) | 117.1 (14.8) | 119.2 (16.3) |
| eGFRcystC ( ml/min/1.73m2) | 102.4 (13.5) | 102.5 (14.7) |
| Microalbuminuria, n (%) | 24 (8.7) | 279 (7.2) |
*
Values are frequency counts and percentages for categorical variables, means (SD) for continuous variables with a normal distribution, or medians (25th to 75th percentiles) for continuous variables with a skewed distribution. Values are based on the original data. Folate deficiency was defined as a folate concentration < 7 nmol/l. Abbreviations: GFRcreat estimated glomerular filtration rate calculated based on creatinine blood levels: eGFRcystC estimated glomerular filtration rate calculated based on cystatin C blood levels.