Fig. 1: Monthly cumulative incidence (%) of perinatal outcomes.

Stillbirth, preterm birth (<34 weeks’ and 34⁺⁰ –36⁺⁶  weeks) and admission to a neonatal unit is shown by symptom status with asymptomatic women in the upper panel and symptomatic women in the lower panel. Number of women admitted to hospital for each month from March 2020 to March 2022 is shown on Y axis to the right. Vaccination status among included women by minimum number of doses recorded; at least 1 dose, 2 doses or 3 doses (%) is shown in the dotted lines. The vertical dashed lines indicate key vaccination policies: The first COVID-19 vaccine in pregnancy was administered in the U.K. in December 31, 2020, and pregnant women were included as priority group by the Joint Committee on Vaccination and Immunisation (JCVI) in the U.K in December 2021. The dominant SARS-CoV-2 variant is indicated by the background colour; wild-type, alpha, delta and omicron.