COVID-19 pandemic impact on preterm birth and stillbirth rates associated with socioeconomic disparities: A quasi-experimental study

Background Conflicting evidence exists on the impact of the COVID-19 pandemic restrictions on preterm birth (PTB) and stillbirth rates. We aimed to evaluate changes in PTB and stillbirth rates before and during the pandemic period and assess the potential effect modification of socioeconomic status (SES). Methods Using the linked administrative health databases from Manitoba, Canada, we conducted a quasi-experimental study among all pregnant women, comparing 3.5 years pre-pandemic (1 October 2016 to 29 February 2020) to the first year of the pandemic (1 March 2020 to 31 March 2021). We used interrupted time series analysis using autoregressive integrated moving average models to assess the quarterly rates of PTB (<37 weeks) and stillbirths. We calculated the predicted trends based on pre-pandemic period data. Finally, we evaluated the lower and higher SES (average annual household income) using subgroup analysis and interaction models. Results We examined 70,931 pregnancies in Manitoba during the study period. Following the implementation of COVID-19 restrictions in March 2020, there were no statistically significant changes in the rates of both PTB (p=0.094) and stillbirths (p=0.958). However, over the pandemic, the PTB rate significantly decreased as a rebound effect by 0.63% per quarter(p=0.005); whereas the stillbirth rate did not change significantly (p=0.878) compared to pre-pandemic period. During the first quarter of 2021, the absolute differences in the observed and expected PTB and stillbirth percentages were 2.05% and 0.04%, respectively. We observed a statistically significant effect modification by SES for PTB rates (p=0.047). Conclusion While the onset of COVID-19 pandemic restrictions was not associated with significant effects on PTB and stillbirth rates, we observed a statistically significant rebound effect on PTB rates. The impact of COVID-19 on preterm birth was dependent on SES, with higher influence on families with lower SES. Further studies are needed to detect future trend changes during pandemic waves after 2021 and assess potential underlying mechanisms. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by a research grant from Research Manitoba. The authors have no financial relationships relevant to this article to disclose. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: University of Manitoba Health Research Ethics Board (HREB) AND Health Information Privacy Committee (HIPC) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data used in this article was derived from administrative health and social data as a secondary source. The data was provided under specific data sharing agreements only for approved use at Manitoba Centre for Health Policy (MCHP). The original source data is not owned by the researchers or MCHP and as such cannot be provided to a public repository. The original data source and approval for use has been noted in the acknowledgments of the article. Where necessary, source data specific to this article or project may be reviewed at MCHP with the consent of the original data providers, along with the required privacy and ethical review bodies. Statistical and anonymous aggregate data associated with this paper, along with metadata describing the original source, has been submitted to MCHP.