Relationship between serum and follicular fluid 25-hydroxyvitamin D levels and pregnancy outcome after in vitro fertilization and embryo transfer

Objective To investigate the relationship between 25-hydroxy vitamin D [25(OH)D)] in blood and follicular fluid and pregnancy outcome after in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET). Methods A prospective cohort study of 201 infertility patients who were treated with IVF/ICSI-ET due to fallopian tube factors in Department of Reproductive Medicine, Xiangya Hospital, Central South University was performed. The cut-off values of 25(OH)D levels in serum and follicular fluid were determined by the method of minimizing P value. The correlations was studied between serum or follicular fluid levels of 25(OH)D and age, body mass index (BMI), past IVF history,endometrial thickness on human chorionic gonadotropin (hCG) injection day, gonadotropin (Gn), progesterone, estradiol, number of retrieved oocytes, and MII oocytes, normal fertilization rate, day 3 high-quality embryo rate, embryo implantation rate, clinical pregnancy rate and early abortion rate. Binary logistic regression analysis of influencing factors of pregnancy outcome was done. Results 1)The serum 25(OH)D level was 16.4(13.1, 20.2) μg/L and the follicular fluid 25(OH)D was 15.3(11.6,20.3) μg/L. There was a significant linear correlation between the two groups (r=0.78, P<0.001). 2)The clinical pregnancy rate (33.87%) and the embryo implantation rate (25.44%) in the low level group of 25(OH)D in serum were lower than those in the high level group (52.52%, P=0.014; 40.24%, P=0.006). The clinical pregnancy rate (39.39%) and the embryo implantation rate (30.22%) in the low level group of 25(OH)D in follicular fluid were lower than those in the high level group (53.92%, P=0.039; 40.98%, P=0.032). The early abortion rate in the low level group of 25(OH)D in follicular fluid (17.95%) was higher than that in the high level group (7.27%, P=0.002). 3) The results of two classification logistic regression analysis showed that the levels of 25(OH)D in serum and follicular fluid were related to clinical pregnancy outcome (P=0.016, P=0.020). Conclusion There was a significant linear correlation between 25(OH)D in serum and that in follicular fluid. The levels of 25(OH)D in serum and follicular fluid were correlated with the pregnancy outcome of IVF/ICSI-ET. Key words: Fertilization in vitro; Embryo transfer; 25-hydroxy vitamin D; Pregnancy outcome