Effect of prolonged hospitalization for threatened preterm labor on maternal and fetal vitamin D levels

Aim We aimed to evaluate the effect of prolonged hospitalization for threatened preterm labor (TPL) on maternal and fetal vitamin D status. Methods This was a retrospective cohort study, spanning 4 years, including 18 women with TPL and 36 women with normal pregnancy who received prenatal care for a singleton pregnancy at our center. TPL cases were women who were admitted to our hospital after the second trimester test for at least 28 days, during which time the third trimester test was also performed. Controls were randomly sampled from women matched for age as well as the season during which the third trimester test was performed. Serum 25‐hydroxyvitamin D (25(OH)D) concentration in maternal blood was compared between the two groups at second trimester, third trimester and in the umbilical cord blood at delivery. Results The mean ± SD of maternal serum 25(OH)D concentration in the TPL group (14.0 ± 3.0 ng/mL) was significantly lower than that in the control group (17.8 ± 5.9 ng/mL) (P < 0.01) in the third trimester, although there was no significant difference in the second trimester (P = 0.30). There was a significant reduction (P < 0.01) in the maternal serum 25(OH)D from the second to third trimester in the TPL group, compared to the control group (P = 0.60). There was no significant difference between the two groups in umbilical cord blood 25(OH)D concentrations at delivery (P = 0.41). Conclusion Prolonged hospitalization for TPL reduced the maternal vitamin D status but did not influence the neonatal status at delivery.