Background: Exposure to cigarette smoke during pregnancy leads to several adverse effects on mother and child. The purpose of this study was to evaluate the effect of being a passive smoker during pregnancy on vitamin D level and related biochemical indices including parathyroid hormone, calcium, phosphorus and alkaline phosphatase in mothers and newborns.
Methods: One hundred eight pregnant women and their newborns participated in a historical cohort study in two equal groups (n = 54) with and without cigarette smoke exposure. Maternal blood and urine samples and blood samples of umbilical cord were obtained in the delivery room. Concentration of 25-hydroxy vitamin D and related biochemical indices in samples of maternal and cord blood were investigated. Exposure to cigarette smoke was evaluated through questionnaire and maternal urine and umbilical cord serum cotinine levels.
Results: The mean level of 25-hydroxyvitamin D in maternal serum was 9.28 ± 5.19 ng/mlin exposed and 10.75 ± 5.26 ng/ml in non-exposed group(p > 0.05). The mean concentration of 25-hydroxy vitamin D in cord serum was 10.83 ± 6.68 ng/ml in the exposed and 11.05 ± 4.99 ng/ml in the non-exposed group(p > 0.05). The exposed mothers had significantly higher parathyroid hormone level (p = 0.013), lower serum calcium (p = 0.024) and higher serum alkaline phosphatase (p = 0.024). There was a significant correlation between maternal and umbilical cord serum 25-hydroxyvitamin D within both exposed and non-exposed groups (p < 0.001).
Conclusion: Maternal exposure to cigarette smoking during pregnancy negatively influences serum calcium level and increase parathyroid hormone and alkaline phosphatase in mothers.