ObjectiveTo determine the impact of maternal coronavirus disease 2019 (COVID‐19) on prematurity, birthweight and obstetric complications.DesignNationwide, population‐based retrospective cohort study.SettingNational Programme de Médicalisation des Systèmes d'Information database in France.PopulationAll single births from March to December 2020: 510 387 deliveries, including 2927 (0.6%) with confirmed COVID‐19 in the mother and/or the newborn.MethodsThe group with COVID‐19 was compared with the group without COVID‐19 using the chi‐square test or Fisher's exact test, and the Student's t test or Mann–Whitney U test. Logistic regressions were used to study the effect of COVID‐19 on the risk of prematurity or macrosomia (birthweight ≥4500 g).Main outcome measuresPrematurity less than 37, less than 28, 28–31, or 32–36 weeks of gestation; birthweight; obstetric complications.ResultsIn singleton pregnancies, COVID‐19 was associated with obstetric complications such as hypertension (2.8% versus 2.0%, p < 0.01), pre‐eclampsia (3.6% versus 2.0%, p < 0.01), diabetes (18.8% versus 14.4%, p < 0.01) and caesarean delivery (26.8% versus 19.7%, p < 0.01). Among pregnant women with COVID‐19, there was more prematurity between 28 and 31 weeks of gestation (1.3% versus 0.6%, p < 0.01) and between 32 and 36 weeks of gestation (7.7% versus 4.3%, p < 0.01), and more macrosomia (1.0% versus 0.7%, p = 0.04), but there was no difference in small‐for‐gestational‐age newborns (6.3% versus 8.7%, p = 0.15). Logistic regression analysis for prematurity showed an adjusted odds ratio (aOR) of 1.77 (95% CI 1.55–2.01) for COVID‐19. For macrosomia, COVID‐19 resulted in non‐significant aOR of 1.38 (95% CI 0.95–2.00).ConclusionsCOVID‐19 is a risk factor for prematurity, even after adjustment for other risk factors.Tweetable The risk of prematurity is twice as high in women with COVID‐19 after adjustment for factors usually associated with prematurity.