Table 2.
Characteristics of Mothers and Children by Categories of Maternal 25(OH)-vitamin D (n=3,825), U.S. Collaborative Perinatal Project (1959–73)
| Categories of maternal 25(OH)-vitamin D (nmol/l) | ||||
|---|---|---|---|---|
| Category 1 (<25) |
Category 2 (25–<50) |
Category 3 (50–<75) |
Category 4 (≥75) |
|
| 25(OH)-vitamin D concentration (nmol/l) (mean, SD) | 18 (5) | 37 (7) | 61 (7) | 98 (23) |
| n (%) | ||||
| Maternal educationa - <12 years | 436 (67.9) | 950 (60.3) | 491 (50.0) | 262 (44.9) |
| 12 years | 169 (26.3) | 490 (31.1) | 349 (35.5) | 206 (35.3) |
| ≥13 years | 37 (5.8) | 135 (8.6) | 142 (14.5) | 115 (19.7) |
| Maternal agea - <20 | 215 (33.3) | 485 (30.4) | 240 (24.0) | 128 (21.8) |
| 20–29 | 323 (50.2) | 855 (53.6) | 591 (59.2) | 357 (60.9) |
| 30–34 | 64 (9.9) | 159 (10.0) | 111 (11.1) | 61 (10.4) |
| ≥35 | 42 (6.5) | 97 (6.1) | 57 (5.7) | 40 (6.8) |
| Parityb - 0 | 233 (36.3) | 557 (34.9) | 386 (38.7) | 208 (35.6) |
| 1 | 127 (19.8) | 367 (23.0) | 238 (23.9) | 152 (26.0) |
| ≥2 | 282 (43.9) | 671 (42.1) | 373 (37.4) | 225 (38.5) |
| Race and ethnicitya – Black | 481 (74.7) | 909 (57.0) | 361 (36.1) | 152 (25.9) |
| White | 127 (19.7) | 559 (35.0) | 569 (57.0) | 398 (67.9) |
| Puerto Rican | 36 (5.6) | 128 (8.0) | 69 (6.9) | 36 (6.1) |
| Maternal pre-pregnancy BMIb - Underweight (<18.5) | 61 (10.1) | 180 (11.9) | 96 (10.5) | 60 (11.0) |
| Normal weight (18.5–24.9) | 414 (68.4) | 1037 (68.3) | 676 (73.6) | 402 (73.9) |
| Overweight (25.0–29.9) | 92 (15.2) | 226 (14.9) | 111 (12.1) | 59 (10.9) |
| Obese (≥30) | 38 (6.3) | 76 (5.0) | 36 (3.9) | 23 (4.2) |
| Marital status – marrieda | 439 (68.2) | 1225 (76.8) | 835 (83.6) | 508 (86.7) |
| Smoker - yes | 323 (50.5) | 753 (47.3) | 459 (46.2) | 252 (43.0) |
| Gestational age at birtha,c - <32 weeks’ | 43 (6.7) | 106 (6.6) | 53 (5.3) | 23 (3.9) |
| 32–36 | 192 (29.8) | 437 (27.4) | 239 (23.9) | 139 (23.7) |
| 37–40 | 260 (40.4) | 619 (38.8) | 411 (41.1) | 235 (40.1) |
| ≥41 | 149 (23.1) | 434 (27.2) | 296 (29.6) | 189 (32.3) |
| Trimester of blood collectiona – 1st trimester | 88 (13.7) | 231 (14.5) | 167 (16.7) | 67 (11.4) |
| 2nd trimester | 556 (86.3) | 1365 (85.5) | 832 (83.3) | 519 (88.6) |
| Season of blood collectiona – Winter | 215 (33.4) | 401 (25.1) | 190 (19.0) | 79 (13.5) |
| Spring | 241 (37.4) | 432 (27.1) | 226 (22.6) | 81 (13.8) |
| Summer | 100 (15.5) | 395 (24.8) | 295 (29.5) | 218 (37.2) |
| Fall | 88 (13.7) | 368 (23.1) | 288 (28.8) | 208 (35.5) |
| Maternal pre-eclampsia | 108 (16.8) | 271 (17.0) | 154 (15.4) | 98 (16.8) |
43 women were missing data for education, 6 for parity, 238 for BMI, 14 for smoking, 4 for pre-eclampsia.
a
χ2 p-value <0.01,
b
p<0.05
c
median gestational age was 39 weeks (inter-quartile range=5)