calcium‑vitamin d co‑supplementation affects metabolic profiles, but not pregnancy outcomes, in healthy pregnant women

background: pregnancy is associated with unfavorable metabolic profile, which might in turn result in adverse pregnancy outcomes. the current study was designed to evaluate the effects of calcium plus vitamin d administration on metabolic status and pregnancy outcomes in healthy pregnant women. methods: this randomized double‑blind placebo‑controlled clinical trial was performed among 42 pregnant women aged 18–40 years who were at week 25 of gestation. subjects were randomly allocated to consume either 500 mg calcium‑200 iu cholecalciferol supplements (n = 21) or placebo (n = 21) for 9 weeks. blood samples were obtained at the onset of the study and after 9‑week trial to determine related markers. post‑delivery, the newborn’s weight, length, and head circumference were measured during the first 24 h after birth. results: consumption of calcium‑vitamin d co-supplements resulted in a significant reduction of serum high‑sensitivity c‑reactive protein levels compared with placebo (−1856.8 ± 2657.7 vs.707.1 ± 3139.4 μg/ml, p = 0.006). we also found a significant elevation of plasma total antioxidant capacity (89.3 ± 118.0 vs. −9.4 ± 164.9 mmol/l, p = 0.03), serum 25‑hydroxyvitamin d (2.5 ± 3.5 vs. −1.7 ± 1.7 ng/ml, p < 0.0001), and calcium levels (0.6 ± 0.6 vs. −0.1 ± 0.4 mg/dl, p < 0.0001). the supplementation led to a significant decrease in diastolic blood pressure (−1.9 ± 8.3 vs. 3.1 ± 5.2 mmhg, p = 0.02) compared with placebo. no significant effect of calcium‑vitamin d co-supplements was seen on other metabolic profiles. we saw no significant change of the co‑supplementation on pregnancy outcomes as well. conclusions: although calcium‑vitamin d co‑supplementation for 9 weeks in pregnant women resulted in improved metabolic profiles, it did not affect pregnancy outcomes.