Conclusion
Within a large dataset of birth records from South China, we found that COVID-19 lockdown was associated with a slightly shorter gestational length and a moderately higher risk of PTB. Early and middle pregnancy might be a more susceptible exposure window. The COVID-19 control measures were implemented in many countries to reduce the spread of infections and related morbidities. Meanwhile, the incidence of PTB remains high globally, and options for the prevention of PTB are very limited (44). Our findings suggest more attention and efforts are needed to support pregnant women during the lockdown, particularly for those with previous PTB as they are more susceptible (45). Health professionals should make appropriate and timely treatment decisions for pregnant women during the lockdown.