Maternal smoking and the vitamin D-parathyroid hormone system during the perinatal period.

Objective: To evaluate the effect of smoking on the vitamin D-parathyroid hormone (PTH) system during the perinatal period.

Study Design: Sixty-one healthy women with singleton pregnancies and their newborns participated in a cohort study. We compared serum PTH and BsmI polymorphism of the vitamin D receptor gene, 25 hydroxyvitamin D (25(OH)D), 1,25 dihydroxyvitamin D, calcium, phosphorus, and bone alkaline phosphatase (bALP) in a smoking group (n = 32) versus a non-smoking group (n = 29), controlling for lifestyle confounders. The mothers were examined at 30 to 32 weeks and 38 to 40 weeks of pregnancy, and the infants were examined at 2 to 3 days of postnatal life.

Results: Mothers who smoked and their newborns showed decreased serum PTH (30-32 weeks, 26.9 +/- 10.7 pg/mL versus 37.1+/-19.5 pg/mL; 38-40 weeks, 32.2 +/- 13.5 pg/mL versus 46.2 +/- 21.9 pg/mL, P = .005; newborns, 43.4 +/- 21.8 versus 64.1 +/- 34.2 pg/mL, P = .02) and increased phosphorus. Newborns of mothers who smoked also had significantly lower anthropometric measurements and serum 25(OH)D (14.2 +/- 6.2 ng/mL versus 22.3 +/- 11.3 ng/mL, P = .009). In addition, pregnant women who smoked had lower bALP (30-32 weeks, 31 +/- 15 U/L versus 44+/-29 U/L; 38-40 weeks, 55 +/- 32 U/L versus 97 +/- 62 U/L, P = .005).

Conclusions: Smoking during pregnancy negatively influences calcium-regulating hormones, leading to relative hypoparathyroidism in both the mother and their newborns.