COVID-19 and pregnancy: A comparison of case reports, case series and registry studies

Case reports and retrospective series published early on in the COVID-19 pandemic had useful information, but overestimated maternal, fetal and neonatal complications related to COVID-19 infection when compared with later prospective registries.

Keelin O'Donoghue
Journal Name
European Journal of Obstetrics, Gynecology, and Reproductive Biology (EJOG)
Journal Article
COVID-19, Stillbirth
Full Citation
Young EM, Green O, Stewart J, King Y, O'Donoghue K, Walker KF, Thornton JG. COVID-19 and pregnancy: A comparison of case reports, case series and registry studies. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2022;268:135-142.
Link to Publication


Many case reports and series of cases were published early on in the COVID-19 pandemic when the disease was new and all the information about it was needed. This approach can lead to bias as small numbers of cases with poor outcomes are always more likely to be reported on and published. This study searched a large database of primary sources of published paper to compare the reporting of COVID-19 in pregnancy in 149 case reports, case series and Registries over the first 8 months of the pandemic. Reports of neonatal and maternal death, as well as preterm birth, maternal ICU admission and stillbirth were selected for comparison. All complications were more common in case reports, and in retrospective series compared with prospective registry studies. The later also revealed extensive overlap in their case reporting and only one national registry of COVID-19 in pregnancy removed duplicate cases. Higher rates of complications seen in case reports and series are likely due to selection or publication bias and registry studies. Although not perfect, Registry studies are likely to give the most accurate information about complications from COVID-19 in pregnancy.

Pregnancy Loss Research Group

Pregnancy Loss Research Group, Department of Obstetrics & Gynaecology, University College Cork, Fifth Floor, Cork University Maternity Hospital, Wilton, Cork, T12 YE02, Ireland,