TABLE 3.

Effect of vitamin D supplementation^a on changes in maternal blood pressure in intervals across pregnancy, n = 1257

	SBP Δ per week (mmHg)b			DBP Δ per week (mmHg)b
Gestational age	β	95% CI	P valuec	β	95% CI	P valuec
24–30 weeks
Placebo	ref			ref
4200 IU/week	−0.042	(−0.382 to 0.299)	0.810	−0.038	(−0.311 to 0.235)	0.785
16 800 IU/week	0.018	(−0.327 to 0.362)	0.920	0.034	(−0.242 to 0.310)	0.811
28 000 IU/week	0.130	(−0.166 to 0.426)	0.389	0.103	(−0.134 to 0.341)	0.393
30–36 weeks
Placebo	ref			ref
4200 IU/week	0.209	(−0.116 to 0.533)	0.207	0.108	(−0.152 to 0.369)	0.416
16800 IU/week	−0.009	(−0.336 to 0.317)	0.956	0.040	(−0.222 to 0.302)	0.763
28 000 IU/week	0.176	(−0.107 to 0.459)	0.223	0.186	(−0.041 to 0.413)	0.108
>36 weeks
Placebo	ref			ref
4200 IU/week	0.098	(−0.573 to 0.769)	0.775	−0.038	(−0.576 to 0.500)	0.890
16 800 IU/week	−0.042	(−0.744 to 0.659)	0.906	0.122	(−0.441 to 0.684)	0.672
28 000 IU/week	−0.326	(−0.926 to 0.274)	0.287	−0.073	(−0.554 to 0.409)	0.767

CI, confidence interval; IU, international unit.

^aVitamin D doses were administered weekly within a randomized controlled trial.

^bMixed-effects models with linear spline knots at 30 and 36 weeks gestation were used to estimate effect of vitamin D on changes in SBP or DBP. Models included spline terms for gestational age; treatment groups and interactions terms between treatment group and gestational age spline terms. Models were fit to test the effect of each vitamin D treatment group on SBP or DBP with reference to placebo. Models were adjusted for baseline SBP or DBP and gestational age at enrollment. Estimates for vitamin D groups are the coefficients for the interaction terms between treatment group and gestational age spline terms, which represent the mean change in SBP or DBP between vitamin D groups compared with placebo at specified timepoints. Interclass correlation coefficient: SBP, 0.399; DBP, 0.413.

^cP value is for the interaction term between treatment group and gestational age spline terms.