Objective: To explore the association of the 25-hydroxy vitamin D (25(OH)D) level in the serum with the early pregnancy outcome of frozen-thawed embryo transfer (FET).
Methods: We selected 119 infertile women that underwent FET and detection of serum 25(OH)D in the Department of Reproductive Medicine of the General Hospital of Central Theater Command from April 2020 to December 2021. According the level of serum 25(OH)D, we divided the patients into three groups: 25(OH)D <45.0 nmol/L (n = 59), 25(OH)D 45.0－75.0 nmol/L (n= 47), and 25(OH)D ≥75.0 nmol/L but <375.0 nmol/L) (n = 13), compared the basic information and the rates of clinical pregnancy, embryo implantation and adverse pregnancy among the three groups, and investigated the factors affecting the early pregnancy outcome using binary logistic regression analysis.
Results: No statistically significant differences were observed among the three groups in the age (≤42 yr), body mass index (BMI), endometrial thickness at the transplantation day (≥7 mm), numbers of embryos transferred and high-quality embryos transferred, or rates of clinical pregnancy, embryo implantation and adverse pregnancy (P > 0.05). Binary logistic regression analysis showed that the rate of early clinical pregnancy was significantly correlated with the level of serum 25(OH)D (OR: 1 064, P = 0.040) and the number of high-quality embryos transferred (OR: 0.495, P = 0.004), but not with the age (≤42 yr), BMI, endometrial thickness at the transplantation day (≥ 7 mm), number of embryos transferred, or the levels of E2 and progesterone at the transplantation day (P > 0.05).
Conclusion: The level of serum 25(OH)D is positively correlated with the early pregnancy outcome of FET. A high serum 25 (OH) D level can improve the outcome and can be used as a good indicator to predict the success rate of FET.
Keywords: frozen-thawed embryo transfer; early pregnancy outcome; 25-hydroxy vitamin D.