What is Known: • The aetiologies of preterm birth and stillbirth are multifaceted and linked to a wide range of socio-demographic, medical, obstetric, foetal, psychosocial and environmental factors. • The COVID-19 lockdown saw a reduction in extremely preterm births in Denmark and other high-income countries. An urgent question is whether this reduction can be explained by increased perinatal mortality.

What is New: • The reduction in extremely preterm births during the Danish COVID-19 lockdown was not a consequence of increased perinatal mortality, which remained unchanged during this period. • The stillbirth rate was reduced throughout the extended period of COVID-19 restrictions.