Introduction:
SARS-CoV-2 enters target host cells via the cellular receptor angiotensin-converting enzyme 2 (ACE2) and the cellular protease transmembrane protease serine-2 (TMPRSS2), which are expressed in the endometrium, possibly affecting implantation.
Study Aim:
To study the effect of COVID-19 infection on pregnancy rates in frozen embryo transfer (FET) cycles.
Methods:
A retrospective cohort study including women under the age of 42 with documented COVID-19 up to one year prior to treatment, undergoing FET cycles in the first half of 2021, with transfer of embryos generated prior to the infection. Controls were SARS-CoV-2 non-diagnosed, non-vaccinated women matched by age, number and day of embryo transfer.
Results:
Forty-one Recovered women and 41 controls were included. Pregnancy rates were 29 % and 49% respectively (p=0.070). Stratification by time from SARS-CoV-2 infection to transfer into ≤60 and >60 days revealed a difference in pregnancy rates, with women in the COVID group having lower pregnancy rates if infected in proximity to the transfer (21% vs. 55%; p=0.006). In a logistic regression model, infection was a significant variable (p=0.05, OR 0.325, 95% CI 0.106-0.998). Logistic regression applied on the subgroup of women infected in proximity to the transfer, further strengthened the univariate results, with COVID-19 remaining a significant parameter (p=0.005, OR 0.072, 95% CI 0.012-0.450).
Conclusions:
In FET cycles of patients with past SARS-CoV-2 infection, in which oocytes were retrieved prior to infection, decreased pregnancy rates were observed, specifically in patients who recovered less than 60 days prior to embryo transfer.