Tehran University of Medical Sciences Journal of Family and Reproductive Health 1735-8949 16 4 2022 12 13 290 295 Azadeh Shabani Department of Obstetrics and Gynecology, Shahid Taleghani Hospital, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Amene Abiri Department of Obstetrics and Gynecology, Arash Women’s Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Seyedeh Noushin Ghalandarpoor-Attar Department of Obstetrics and Gynecology, Baqyiatallah Hospital, Faculty of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran Alireza Hadizadeh School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Seyedeh Mojgan Ghalandarpoor-Attar Maternal, Fetal & Neonatal Research Center, Family Health Research Institute, Tehran University of Medical Sciences, Tehran, Iran AND Department of Obstetrics and Gynecology, Baharloo Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran 2022 04 06 2022 07 17 Objective: This descriptive-analytic cross-sectional study aimed to figure out whether maternal serum vitamin D concentration correlates with cervical length measurement in mid-gestation or not. Materials and methods: During Jun-Jan 2021, 213 pregnant women at 18-22 weeks of gestation were investigated. First, demographic features were obtained then, maternal serum vitamin D concentration was measured by enzyme-linked immunoassay and cervical length was measured via transvaginal sonography according to fetal maternal foundation guideline and appropriate statistical test was used to analyze the correlation between maternal vitamin D level and cervical length in mid-pregnancy. Results: It was shown that 29.6% and 25.4% of participants had vitamin D deficiency and insufficiency, respectively. Spearman’s test found no significant correlation between maternal vitamin D level and cervical length in mid-pregnancy. Moreover, cervical length and maternal vitamin D level had no association with maternal BMI. Conclusion: Although maternal vitamin D level and its sufficiency status was not associated with cervical length in mid- pregnancy, as a trend toward decreased maternal serum vitamin D level by advancing gestational age was observed. It may be concluded that it is prolonged vitamin D deficiency during gestation that may lead to cervical length shortening and subsequent preterm delivery later in gestation. https://jfrh.tums.ac.ir/index.php/jfrh/article/view/2065 https://jfrh.tums.ac.ir/index.php/jfrh/article/download/2065/626