['We sought to characterize the relationship between serum 25-hydroxy vitamin D (25-OH D) levels and implantation and clinical pregnancy rates in women who undergo a euploid blastocyst embryo transfer.', "This retrospective cohort study, conducted in an academic setting, included 529 cycles in which comprehensive chromosome screening was performed as part of routine infertility care with an autologous transfer of 1 or 2 euploid blastocysts. After excluding repeat cycles there were 517 unique cycles representing 517 women for evaluation. Vitamin D levels from serum samples obtained on the day of ovulation trigger in the fresh in vitro fertilization cycle were analyzed. The primary outcome was ongoing pregnancy rate as defined by sonographic presence of fetal heart rate at >8 weeks' gestation.", 'For the population as a whole, serum vitamin D ranges and pregnancy outcomes did not correlate. Furthermore, pregnancy rates did not differ when comparing women in different strata of vitamin D levels (<20, 20-29.9, and ≥30 ng/mL). No meaningful breakpoint for vitamin D levels and ongoing pregnancy rate was identified using receiver operating characteristic analysis with the resultant line possessing an area under the curve of 0.502. Multivariate logistic regression controlling for age, transfer order, race, season, and body mass index did not yield a different result. The study was powered to detect an 18% difference in ongoing pregnancy rates between patients grouped by the 3 vitamin D ranges.'] Do vitamin D levels affect IVF outcomes following the transfer of euploid blastocysts?