On March 11, 2020, the World Health Organization declared the outbreak of severe acute respiratory syndromecoronavirus 2 (SARS-CoV-2) a global pandemic, reporting community-scale transmission worldwide with more than 8 million cases of confirmed coronavirus disease (COVID-19). On March 17, the American Society for Reproductive Medicine provided early key recommendations, updated and affirmed on March 30, including suspending initiation of new treatment cycles aimed at achieving pregnancy. The European Society of Human Reproduction and Embryology provided similar recommendations that expanded even further to include consideration of avoidance of spontaneous conception. These recommendations were made in the infancy of the pandemic when little was known about the implications of the novel coronavirus on implantation and pregnancy. Over the past several months, new developments in molecular virology and immunobiology of SARS-CoV-2 have improved our understanding of the novel coronavirus. In light of the rapidly expanding knowledge base and the realization that care cannot be paused indefinitely, fertility clinics around the world are beginning to resume treatment.As fertility care recommences, the potential impact of SARS-CoV-2 on implantation and early pregnancy is increasingly relevant. Understanding the pathophysiology of the virus and the target tissues at a molecular level can help clarify the potential short-and long-term implications of infection on implantation, miscarriage, the intrauterine milieu, the placenta, and pregnancy and neonatal outcomes (1).The genome sequence of SARS-CoV-2 is similar to, but distinct from the two other coronaviruses, as it has about 80% sequence identity with SARS-CoV and about 50% with MERS-Cov-2. Similar to SARS-CoV, the spike (S) protein of SARS-CoV-2 facilitates viral entry into target cells. Entry depends on binding of the S1 subunit of the S protein to a cellular receptor. Multiple studies have also confirmed that SARS-CoV-2 engages angiotensin-converting enzyme 2 (ACE2) as the entry receptor. In addition, viral entry depends on priming cleavage of the S protein, between S1 and S2, and activating cleavage on the S2ʹ site. Depending on virus strains and cell types, proteins may be cleaved by one or several host proteases, including furin, trypsin, cathepsins, transmembrane protease serine protease-2 (TMPRSS2), or TMPRSS4 (2-4).To date, the impact of SARS-CoV-2 on endometrial lining and implantation remains largely unknown, so the study by Henarejos-Castillo et al. ( 5) is of utmost importance. The authors assessed endometrial susceptibility to SARS-CoV-2 infection by measuring endometrial ACE2, TMPRSS2, TMPRSS4, cathepsin B and L (CTSB and CTSL, respectively), FURIN, MX dynamin-like GTPase 1 (MX1), and Basigin (BSG) gene expression. The group used public transcriptomic data sets to evaluate the risk of endometrial SARS-CoV-2 infec-

Preimplantation genetic testing for aneuploidy (PGT-A) seeks to identify embryos with a normal chromosome complement during in vitro fertilization (IVF). Transfer of one euploid embryo at a time maximizes the chance of implantation while minimizing the risk of multiple pregnancy. The emergence of new technologies including next generation sequencing (NGS) has led to increased diagnosis of embryonic mosaicism, suggesting the presence of karyotypically distinct cells within a single trophectoderm (TE). Clinical implications of embryonic mosaicism are important in both naturally conceived and IVF pregnancies. Although information regarding outcomes after mosaic embryo transfer (MET) is limited, more than 100 live births have now been documented with rather reassuring outcomes with no abnormal phenotype. Here, we aim to provide a summary of recent data regarding clinical and neonatal outcomes after transfer of mosaic embryos in IVF/PGT-A cycles.

Splenic artery aneurysm rupture is a rare complication of pregnancy with very high maternal and fetal mortality rate. In this paper, a case of splenic artery aneurysm rupture at 34 weeks of gestation with both maternal and fetal survival is presented.

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