Preserved Prenatal Lung Growth in Fetal MRI Following Mild Omicron Infection During Pregnancy

The COVID-19 pandemic has resulted in severe acute and long-term effects for the respiratory system. With SARS-CoV-2 evolving, the latest omicron variant was described as showing less severe involvement of the lower respiratory tract in adults. Effects in the vulnerable cohort of the unborn, however, remain unknown.We therefore investigated pregnancies with mild SARS-CoV-2 omicron infection using fetal MRI to assess lung volume as a measure of pulmonary growth. In n=24 cases, fetal lung volumes were normalized by estimated fetal weight and described as the percentage of the respective 50th percentile reference values, as well as compared to a site-specific non-COVID control group (n=15).In fetuses exposed to the SARS-CoV-2 omicron variant, lung volume did not differ significantly from both, published reference values (96·3% ± 22·5% of 50th percentile reference values, p=0·430), or fetal lung volumes of a site-specific, non-COVID control group (94·2% ± 18·5% of 50th percentile reference values, p=0·762). When stratifying the results by trimester of infection (first/second and third trimester infection), no significant differences in lung volumes were observed when compared to the site-specific non-COVID control group. This finding is in stark contrast to our previously published data for the alpha variant of the virus, which revealed reduced lung growth with third trimester infection in the pre-vaccination era.Demonstrating preserved lung growth with omicron variant exposure, our findings might reflect tropism-related effects as well as the impact of vaccination, thereby informing counseling and surveillance of affected pregnancies.Funding: The work was supported by grants from the following organizations: Young Investigator Grant by the Helmholtz Association and the Helmholtz Zentrum München, Germany (NWG VH-NG-829: A.H., K.F.), “Physician Scientists for Groundbreaking Projects” at Helmholtz Zentrum München, Munich, Germany (A.H., S.S.), German Center for Lung Research (DZL, Federal Ministry of Education and Research, Germany (BMBF: A.H.)), German Research Fund (DFG, Research Training Group GRK2338: A.H.), Bavarian Ministry for Science and Art (Corona Forschungsprogramm 2021/22: A.H., S.S), as well as the Chan Zuckerberg Initiative 'Mapping the Pediatric Inhalation Interface: Nose, Mouth, and Airways'. Additional financial support was provided by the Stiftung AtemWeg (LSS AIRR: A.H.).Declaration of Interest: All authors declare no conflict of interest.Ethical Approval: The study was approved by the local institutional review board (ethical approval #LMU-207–33).