The effect of coronavirus disease 2019 immunity on frozen-thawed embryo transfer cycles outcome

Objective: To study the effect of patients’ immunization after coronavirus disease 2019 (COVID-19) infection or messenger ribonucleic acid (mRNA) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine on frozen-thawed embryo transfer (FET). Design: Cohort retrospective study. Setting: Tertiary university affiliated medical center. Patient(s): All consecutive patients undergoing FET cycles in our center. The study group (immune group) consisted of patients treated during the COVID-19 pandemic (between January 2021 and August 2021) who either recovered from COVID-19 infection or received the mRNA SARS-CoV-2 vaccine. The control groups consisted of patients treated during the COVID-19 pandemic (between January 2021 and August 2021) but were not infected or did not receive the mRNA SARS-CoV-2 vaccine (not-immune2021 group) and those treated between January 2019 and August 2019 (before the pandemic) (not-immune2019 group). Intervention(s): Frozen-thawed embryo transfer cycles. Main Outcome Measure(s): Ongoing pregnancy rates and FET cycles’ characteristics. Data on patient age and variables related to infertility treatment were collected from the patient records. Result(s): During the study periods, 428 patients underwent 672 FET cycles. The immune group consisted of 141 patients who underwent 264 FET cycles (44 in postinfection and 220 in postvaccination), whereas the not-immune2021 and not-immune2019 groups consisted of 93 and 194 patients undergoing 125 and 283 FET cycles, respectively. Patients’ characteristics and the types of endometrial preparations were comparable between the study groups. The implantation rate and clinical and ongoing pregnancy rates per transfer were similar between the study groups (immune group, postinfection and postvaccination; not-immune2021 group; not-immune2019 group). Conclusion(s): Coronavirus disease 2019 infection or vaccination did not affect patients’ performance or implantation in their subsequent FET cycle.