Association between COVID-19 mitigation measures and preterm birth rate in China

The coronavirus disease 2019 (COVID-19) pandemic led to major lockdowns around the world as a mitigation measure to restrict the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by controlling population flow and contact. Previous studies conducted in Denmark, Ireland, and the Netherlands have shown that the number of preterm births reduced after the implementation of COVID-19 mitigation measures. Conversely, a study from Philadelphia, Pennsylvania in the United States reported no change in preterm birth rates post-lockdown.

A new study published in the British Medical Journal Global Health addresses the effect of COVID-19 mitigation measures on the preterm birth rate in China. Furthermore, the authors of this study analyzed the preterm birth rate after the lockdown was lifted and daily life returned to normal.

Study: Are COVID-19 mitigation measures reducing preterm birth rate in China? Image Credit: M.Moira /

Preterm birth rate and COVID-19 mitigation measures

Normally, a full-term baby is born after at least 37 gestational weeks. Preterm birth occurs between 24 and 37 gestational weeks and can result in perinatal morbidity and mortality. Multiple factors are responsible for preterm birth; therefore, currently available strategies to prevent preterm birth are not particularly effective.

Certain risk factors for preterm birth include asymptomatic infection, intrauterine infections, and inflammation, which can lead to induction of labor. COVID-19 mitigation measures like increased awareness of hygiene, wearing masks, social distancing, staying at home, and lack of population flow reduced exposure to pathogens and risk of infections.

Notably, the incidence of common infectious diseases decreased during the COVID-19 emergency response. Minor accidents among pregnant women were also further reduced due to less work and travel. The lockdown also resulted in more people eating home-cooked meals, getting the optimal amount of sleep, and reduced exposure to air pollution. Overall, the hygiene measures and behavioral changes adopted during the lockdown may affect pregnancy outcomes.

COVID-19 was first reported in China. China was also the first country to implement strict measures and policy responses to avoid the spread of infection. This involved a complete lockdown from January 23, 2020, to May 18, 2020. After the relaxation of mitigation measures, schools, childcare facilities, restaurants, and entertainment places were allowed to reopen and daily life returned to normal.

This short mitigation time window provided a unique opportunity to conduct a natural experiment in which researchers could evaluate the effects of COVID-19 mitigation measures on preterm birth.

About the study

Researchers collected data from Shanghai First Maternity and Infant Hospital (SFMIH), Tongji University School of Medicine on 169,073 deliveries from January 1, 2014, to December 31, 2020. For this study, the researchers excluded multiple pregnancies and deliveries before 24 weeks of gestation.

Also, the pregnant women that were considered in this study were not infected with COVID-19. Taken together, the current study included 164,107 singleton deliveries.

The authors of the current study evaluated the association between the national COVID-19 mitigation measures and the incidence of preterm births using statistical analyses. A total of six time windows were analyzed including 1 month, 2 months, 3 months, 4 months, and 5 months after implementation of mitigation measures, and the last half-year of 2020 when these measures were relaxed. The researchers then compared the period after implementation of the measures to the same periods in each year preceding the COVID-19 pandemic (2014–2019).

It is assumed that due to the relatively short time windows studied, the changes observed in preterm birth are due to the COVID-19 mitigation measures and not due to other interventions or major impacts. Besides, including data from July 2020 to December 2020, which is after restrictions were lifted, ensured that the preterm rates were influenced by the mitigation measures and no other factors.

Reduction in preterm birth rates

The preterm birth rates were generally between 5.2%–5.6% during the entire study period. There were significant reductions in preterm birth since January 23 2020 following COVID-19 mitigation measures, which was consistent in the 2-month, 3-month, 4-month, and 5-month time windows after implementation.

Though preterm births were reduced across various degrees of prematurity, the reduction of moderate-to-late preterm births was statistically significant. Moreover, the reduction in preterm birth rates disappeared after the various restrictions were lifted. In other words, the reduction in preterm birth rates was specific to the lockdown time window.

The researchers also assessed the stillbirth rate across this time window and did not find any association with the lockdown restrictions.

Implications of the study

The current study showed an association between substantial decreases in preterm birth rates and implementation of the national COVID-19 mitigation measures in China. The most important observation of this study was that the reduction in preterm birth rates disappeared after daily life and work returned to normal.

This study has paved the way to further examine the underlying mechanisms associated with this observation and ways in which certain measures can be implemented to prevent preterm births.

Journal reference:
Dr. Shital Sarah Ahaley

Written by

Dr. Shital Sarah Ahaley

Dr. Shital Sarah Ahaley is a medical writer. She completed her Bachelor's and Master's degree in Microbiology at the University of Pune. She then completed her Ph.D. at the Indian Institute of Science, Bengaluru where she studied muscle development and muscle diseases. After her Ph.D., she worked at the Indian Institute of Science, Education, and Research, Pune as a post-doctoral fellow. She then acquired and executed an independent grant from the DBT-Wellcome Trust India Alliance as an Early Career Fellow. Her work focused on RNA binding proteins and Hedgehog signaling.


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