TABLE 2.
Multiple regression analysis of calcium kinetic measures1
| Prepregnancy/first trimester | Third trimester | Postpartum | |
| VO+ (mg/d) | |||
| BA | — | R2 = 0.25 1,25(OH)2D [0.059]* Age [0.096]* | R2 = 0.84 Calcium [0.002] Breastfeeding [0.002]* Ethnicity [0.004] Prepregnancy BMI [0.035]* 25(OH)D [0.047] |
| CA | R2 = 0.59 Calcium [0.016] | None | None |
| BR | R2 = 0.59 Calcium [0.019]Prepregnancy BMI [0.06] | R2 = 0.96 Ethnicity [0.074]* Prepregnancy BMI [0.062] 1,25(OH)2D [0.008]* PTH [0.003] | R2 = 0.99 Ethnicity [0.001] Prepregnancy BMI [0.016] 1,25(OH)2D [0.038]* Calcium [0.0001] PTH [0.0004]* |
| Combined groups | — | R2 = 0.37 Age [<0.0001]* 1,25(OH)2D [0.029]* | R2 = 0.69 Ethnicity [<0.0001] Calcium [0.0003] Breastfeeding [0.0012]* |
| TEP (mg) | |||
| BA | — | R2 = 0.16 Prepregnancy BMI [0.064] | R2 = 0.46 Ethnicity [0.022]* 1,25(OH)2D [0.090]* |
| CA | None | R2 = 0.39 25(OH)D [0.055]* | R2 = 0.58 1,25(OH)2D [0.044] 25(OH)D [0.096] |
| BR | R2 = 0.59 1,25(OH)2D [0.048] Prepregnancy BMI [0.063]* Ethnicity [0.089] | R2 = 0.62 Ethnicity [0.021]* Prepregnancy BMI [0.055] | R2 = 0.55 Prepregnancy BMI [0.023] Ethnicity [0.079]* |
| Combined groups | — | R2 = 0.24 Age [0.010]* Ethnicity [0.056]* Prepregnancy BMI [0.027] | R2 = 0.25 Calcium [0.032] Breastfeeding [0.036]* |
| VO+/TEP | |||
| BA | — | R2 = 0.591,25(OH)2D [0.003]*Calcium [0.004]Prepregnancy BMI [0.002]* | R2 = 0.31 Ethnicity [0.048] |
| CA | R2 = 0.36 Calcium [0.089] | R2 = 0.45 25(OH)D [0.035] | None |
| BR | None | R2 = 0.64 1,25(OH)2D [0.043]* PTH [0.052] | R2 = 0.62 Ethnicity [0.015] Prepregnancy BMI [0.020]* |
| Combined groups | — | R2 = 0.32 Ethnicity [0.002] 1,25(OH)2D [0.018]* Prepregnancy BMI [0.060]* | R2 = 0.42 Ethnicity [<0.0001] |
P values are shown in brackets. Each bone calcium kinetic measurement (dependent variable) was initially related to the following maternal independent variables: age, ethnicity (African compared with non-African), breastfeeding (yes or no), prepregnancy BMI, serum 1,25(OH)2D, serum 25(OH)D, serum PTH, and dietary calcium intake. Independent variables were sequentially removed by backward elimination based on P values. Variables left in the model were significant at the P < 0.10 level. *Denotes a significant inverse association between variables. BA, Baltimore (n = 23; the sample size for the BA cohort during the postpartum period was n = 15); BR, Brazil (n = 10); CA, California (n = 13); PTH, parathyroid hormone; TEP, total exchangeable pool; VO+, bone calcium deposition rate; 1,25(OH)2D, 1,25-dihydroxyvitamin D; 25(OH)D, 25-hydroxyvitamin D.