TABLE 4.
Stepwise regression analysis of pregnant women's third-trimester concentrations of serum total 25(OH)D1
| r 2 | β (95% CI) | P value | |
|---|---|---|---|
| Mean (all trimesters) intake of vitamin D from supplements, IU/d | 0.246 | 0.51 (0.25, 0.71) | <0.0001 |
| Prepregnancy BMI, kg/m2 | 0.052 | −0.23 (−0.44, 0.05) | 0.009 |
| Third-trimester sampling done in winter/spring (vs. summer/fall)2 | 0.042 | −0.21 (−0.44, 0.02) | 0.02 |
| Mean (all trimesters) amount of physical activity, min/d | 0.027 | 0.17 (−0.07, 0.39) | 0.06 |
| University degree (vs. no university degree) | 0.015 | −0.13 (−0.31, 0.12) | 0.15 |
| Total | 0.376 | <0.0001 |
1
n = 79. β coefficients, r2, and P values are not shown for variables that were not included in the regression model (P > 0.25) following the stepwise procedure. Other variables tested in the stepwise procedure were age, primiparity (being pregnant with first child), vitamin D intake from foods, and household income. IU, international units; 25(OH)D, 25-hydroxyvitamin D.
2
Seasons at the time of blood sampling were defined as follows: winter/spring (21 December–20 June), summer/fall (21 June–20 December).