TABLE 1.
Characteristics of participants included in multivariable models of attained serum 25-hydroxyvitamin D concentrations, by time point1
| Maternal delivery | Maternal 6 mo postpartum | Umbilical cord | Infant 6 mo of age | |
|---|---|---|---|---|
| (n = 471) | (n = 541) | (n = 329) | (n = 174) | |
| Maternal characteristics | ||||
| Maternal age,2 y | 22 (20, 26) | 23 (20, 26) | 22 (20, 25) | 23 (20, 27) |
| Maternal height,3 cm | 151.1 ± 5.7 | 151.0 ± 5.6 | 151.2 ± 5.7 | 151.1 ± 5.8 |
| Maternal BMI at enrollment,4 kg/m2 | 23.0 (20.6, 26.3) | 22.9 (20.6, 26.1) | 22.9 (20.6, 26.4) | 23.7 (21.0, 26.5) |
| <18.5, n (%) | 39 (8.3) | 42 (8.1) | 28 (8.5) | 9 (5.5) |
| ≥18.5 to <25, n (%) | 277 (59) | 309 (59) | 189 (57) | 93 (57) |
| ≥25.0 to <30, n (%) | 123 (26) | 142 (27) | 90 (27) | 56 (34) |
| ≥30.0, n (%) | 32 (6.8) | 27 (5.2) | 22 (6.7) | 6 (3.7) |
| Maternal habitual BMI,5 kg/m2 | 23.4 (20.8, 26.5) | 23.4 (20.7, 26.4) | 23.5 (20.9, 26.8) | 23.6 (20.6, 26.8) |
| <18.5, n (%) | 47 (10) | 55 (10) | 35 (11) | 17 (9.8) |
| ≥18.5 to <25, n (%) | 238 (52) | 286 (53) | 162 (51) | 87 (50) |
| ≥25.0 to <30, n (%) | 130 (29) | 156 (29) | 89 (28) | 54 (31) |
| ≥30.0, n (%) | 40 (8.8) | 44 (8.1) | 32 (10) | 16 (9.2) |
| Gestational age at enrollment, wk | 21 (19,22) | 20 (19,22) | 20 (19,22) | 20 (19,22) |
| Parity,6,7n (%) | ||||
| Primiparous | 225 (48) | 249 (46) | 157 (48) | 70 (40) |
| Multiparous | 246 (52) | 292 (54) | 172 (52) | 104 (60) |
| Asset index quintile,8n (%) | ||||
| Q1 | 90 (19) | 108 (20) | 67 (20) | 40 (23) |
| Q2 | 85 (18) | 88 (16) | 64 (19) | 31 (18) |
| Q3 | 85 (18) | 104 (19) | 57 (17) | 33 (19) |
| Q4 | 108 (23) | 127 (23) | 75 (23) | 41 (24) |
| Q5 | 103 (22) | 114 (21) | 66 (20) | 29 (17) |
| Maternal education level, n (%) | ||||
| No education | 20 (4.2) | 21 (3.9) | 13 (4) | 7 (4) |
| Primary; incomplete (grades 1–4) | 93 (20) | 107 (20) | 62 (19) | 36 (21) |
| Primary; complete (grade 5) | 69 (15) | 77 (14) | 49 (15) | 26 (15) |
| Secondary; incomplete (grades 6–9) | 168 (36) | 206 (38) | 114 (35) | 68 (39) |
| Secondary; complete or higher | 121 (26) | 130 (24) | 91 (28) | 37 (21) |
| Vitamin D intervention group,9n (%) | ||||
| 0:0 IU/wk | 92 (20) | 105 (19) | 59 (18) | 38 (22) |
| 4200:0 IU/wk | 93 (20) | 104 (19) | 67 (20) | 31 (18) |
| 16,800:0 IU/wk | 106 (23) | 119 (22) | 78 (24) | 40 (23) |
| 28,000:0 IU/wk | 83 (18) | 104 (19) | 57 (17) | 36 (21) |
| 28,000:28,000 IU/wk | 97 (21) | 109 (20) | 68 (21) | 29 (17) |
| Enrollment serum 25(OH)D,10 nmol/L | 27.1 ± 14.4 | 26.8 ± 14.2 | 27.3 ± 14.7 | 26.6 ± 15.1 |
| Enrollment serum 25(OH)D <30 nmol/L,10n (%) | 306 (65) | 351 (65) | 213 (65) | 115 (66) |
| Prenatal calcium intake,11 mg/d | 979 ± 267 | 992 ± 280 | 991 ± 245 | 1031 ± 314 |
| Adherent to trial supplementation,12n (%) | 455 (97) | 528 (98) | 319 (97) | 172 (99) |
| Infant characteristics | ||||
| Sex | ||||
| Male | 254 (54) | 283 (52) | 174 (53) | 87 (50) |
| Female | 217 (46) | 258 (48) | 155 (47) | 87 (50) |
| Gestational age at birth, wk | 39 (38, 40) | 39 (38, 40) | 39 (38, 40) | 39 (38, 40) |
| Birth weight,13 g | 2736 ± 341 | 2720 ± 341 | 2744 ± 346 | 2715 ± 364 |
Participants were considered eligible for inclusion in the present analysis provided a 25-hydroxyvitamin D measurement was available for 2 consecutive study time points (enrollment, delivery, umbilical cord, and 6 mo postdelivery), to account for effect modification by baseline (or preintervention) concentrations between each dosing interval. Inclusion in adjusted multivariable models (Models C and D) was dependent on data availability for corresponding covariates. 25(OH)D, 25-hydroxyvitamin D.
Data are presented as median (25th percentile, 75th percentile) (all such values).
Data are presented as mean ± SD (all such values).
n = 520 for analyses at 6 mo postpartum and n = 164 for infants at 6 mo of age.
BMI at 12 mo postpartum as a proxy for habitual BMI in the nonpregnant, nonlactating state; n = 455 for analyses at delivery and n = 318 for umbilical cord.
Data are presented as number (%) (all such values).
Defined based on the total number of previous live births, irrespective of previous miscarriage or abortions, and was inclusive of the current pregnancy. Hence, parity was categorized as primiparous (no previous live birth) or multiparous (≥1 live birth).
Determined by ownership of household items, using principal components analysis.
Denotes dose provided prenatally; dose provided postnatally.
n = 537 for analyses at 6 mo postpartum, n = 327 for umbilical cord, and n = 173 for infants at 6 mo of age.
Estimated by a targeted, nonquantitative FFQ, including calcium supplementation of 500 mg/d provided to all participants throughout the intervention period.
Defined a priori as consumption of ≥80% of scheduled tablets.
n = 414 for analyses among women at delivery and n = 472 among women at 6 mo postpartum.