SARS-CoV-2 and pregnancy outcomes under universal and non-universal testing in Sweden: register-based nationwide cohort study.

Objective To assess associations of SARS-CoV-2-infection and pregnancy outcomes considering testing policy and test-positivity-to-delivery-interval. Design Nationwide cohort study. Setting Sweden. Population From the Pregnancy-Register we identified 88,593 singleton births, March 11, 2020-January 31, 2021, linked to data on SARS-CoV-2-positivity from the Public Health Agency, and information on neonatal care admission from the Neonatal Quality-Register. Adjusted odds ratios (aORs) were estimated stratified by testing-policy and test-positivity-to-delivery-interval. Main outcome measures 5-minute Apgar score, neonatal care admission, stillbirth and preterm birth. Results During pregnancy, SARS-CoV-2 test-positivity was 5.4% (794/14,665) under universal and 1.9% (1402/73,928) under non-universal testing. There were generally lower risks associated with SARS-CoV-2 under universal than non-universal testing. In women testing positive >10 days from delivery, generally no significant differences in risk were observed under either testing policy. Neonatal care admission was more common (15.3% vs. 8.0%; aOR 2.24, 1.62-3.11) in women testing positive ≤10 days before delivery under universal testing. There was no significant association with 5-minute Apgar score Conclusions Testing policy and timing of test positivity impact associations between SARS-CoV-2 positivity and pregnancy outcomes. Under non-universal testing, women with complications near delivery are more likely to be tested than women without complications, thereby inflating any association with adverse pregnancy outcomes compared to findings under universal testing.