Table 3:
Seasonally-independent factors associated with third trimester serum 25(OH)D concentration
| Seasonally-adjusted | Seasonally+multivariable-adjusted | |||||||
|---|---|---|---|---|---|---|---|---|
| Characteristic | Location | β | SE | p | β | SE | p | |
| Study location (ref: Ulaanbaatar) | Bulgan | Mongolia | 1.0 | 0.8 | 0.20 | 0.4 | 1.0 | 0.72 |
| Selenge | 1.4 | 0.9 | 0.14 | 4.1 | 1.4 | 0.00 | ||
| Maternal age (years) | Boston | 0.3 | 0.2 | 0.04 | 0.2 | 0.2 | 0.41 | |
| Mongolia | 0.0 | 0.1 | 0.76 | −0.0 | 0.1 | 0.89 | ||
| Not white | Boston | −3.1 | 1.9 | 0.09 | −0.6 | 2.0 | 0.77 | |
| Gestation length at 3rd trimester assessment (months) | Boston | 0.0 | 4.6 | 0.99 | −3.6 | 4.6 | 0.44 | |
| Mongolia | −0.4 | 0.6 | 0.45 | −0.6 | 0.6 | 0.29 | ||
| Gravidity (including current pregnancy) (ref: 0) | 1 | Boston | −0.4 | 2.6 | 0.88 | −1.6 | 2.5 | 0.54 |
| Mongolia | 0.3 | 0.9 | 0.77 | 0.0 | 1.0 | 0.99 | ||
| 2 | Boston | −0.5 | 2.6 | 0.85 | −1.9 | 2.5 | 0.45 | |
| Mongolia | 0.4 | 1.0 | 0.71 | −0.2 | 1.1 | 0.83 | ||
| 3+ | Boston | −5.8 | 2.7 | 0.03 | −7.5 | 2.6 | 0.00 | |
| Mongolia | 0.4 | 0.9 | 0.67 | 0.1 | 1.1 | 0.90 | ||
| Pre-pregnancy BMI | Boston | −0.3 | 0.2 | 0.05 | −0.2 | 0.2 | 0.23 | |
| Mongolia | 0.1 | 0.1 | 0.54 | 0.0 | 0.1 | 0.64 | ||
| 3rd trimester BMI | Boston | −0.3 | 0.1 | 0.04 | ||||
| Mongolia | 0.1 | 0.1 | 0.48 | |||||
| Pre-pregnancy to 3rd trimester change in BMI | Boston | 0.2 | 0.4 | 0.60 | −0.3 | 0.4 | 0.48 | |
| Mongolia | 0.0 | 0.2 | 0.81 | 0.01 | 0.17 | 0.94 | ||
| No college or university degree | Boston | 4.5 | 1.9 | 0.02 | 2.0 | 2.7 | 0.45 | |
| Mongolia | 0.0 | 0.7 | 0.95 | 0.5 | 0.8 | 0.53 | ||
| Not currently married | Boston | 2.7 | 2.3 | 0.23 | −1.2 | 3.0 | 0.68 | |
| Mongolia | −1.9 | 2.1 | 0.35 | −2.1 | 2.5 | 0.41 | ||
| Supplement use during pregnancy (ref: None) | Multivitamin only | Mongolia | 2.0 | 0.9 | 0.03 | 1.7 | 1.0 | 0.08 |
| Vitamin D (with or without multivitamin) | 1.2 | 1.2 | 0.33 | −2.0 | 1.7 | 0.26 | ||
| Drank alcohol or smoked during pregnancy | Boston | −1.3 | 2.6 | 0.62 | −0.1 | 2.5 | 0.97 | |
| Mongolia | 1.6 | 1.3 | 0.20 | 2.0 | 1.3 | 0.14 | ||
Footnote: N, Boston=206; N, Mongolia=390. BMI: body mass index. Statistics are derived from quantile regression estimating median serum 25(OH)D concentration in separate models for Boston and Mongolia, adjusting for either month of assessment alone using a single 12-category variable, or both month of assessment and all other factors in the table (the variable study location is not applicable to and is excluded from all Boston analyses; 3rd trimester BMI is excluded from all multivariable-adjusted analyses due to multicollinearity). Shading: p<0.05. Not shown: in Boston analyses, the square of 3rd trimester BMI is marginally significant in seasonally-adjusted analysis (β=−0.02, SE=0.01, p=0.07) and interaction between 3+ gravidity and “not currently married” is significant in multivariable-adjusted analysis (β=−16.1, SE=7.0, p=0.02).