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Table.  Multivariable Generalized Estimating Equation Logistic Regression Analyses to Determine the Odds of Adverse Perinatal Outcomes During the Pandemic Period Compared With the Historical Period
Multivariable Generalized Estimating Equation Logistic Regression Analyses to Determine the Odds of Adverse Perinatal Outcomes During the Pandemic Period Compared With the Historical Period
1.
Hedermann  G, Hedley  PL, Baekvad-Hansen  M,  et al.  Danish premature birth rates during the COVID-19 lockdown.   Arch Dis Child Fetal Neonatal Ed 2021;106(1):93-95. doi:10.1136/archdischild-2020-319990PubMedGoogle ScholarCrossref
2.
Philip  RK, Purtill  H, Reidy  E,  et al.  Unprecedented reduction in births of very low birthweight (VLBW) and extremely low birthweight (ELBW) infants during the COVID-19 lockdown in Ireland: a ‘natural experiment’ allowing analysis of data from the prior two decades.   BMJ Glob Health. 2020;5(9):e003075. doi:10.1136/bmjgh-2020-003075PubMedGoogle Scholar
3.
Khalil  A, von Dadelszen  P, Draycott  T, Ugwumadu  A, O’Brien  P, Magee  L.  Change in the incidence of stillbirth and preterm delivery during the COVID-19 pandemic.   JAMA. 2020;324(7):705-706. doi:10.1001/jama.2020.12746PubMedGoogle ScholarCrossref
4.
Joseph  KS, Fahey  J; Canadian Perinatal Surveillance System.  Validation of perinatal data in the Discharge Abstract Database of the Canadian Institute for Health Information.   Chronic Dis Can. 2009;29(3):96-100. doi:10.24095/hpcdp.29.3.01PubMedGoogle ScholarCrossref
5.
Knottnerus  A, Tugwell  P.  STROBE—a checklist to Strengthen the Reporting of Observational Studies in Epidemiology.   J Clin Epidemiol. 2008;61(4):323. doi:10.1016/j.jclinepi.2007.11.006PubMedGoogle ScholarCrossref
6.
Pasternak  B, Neovius  M, Söderling  J,  et al.  Preterm birth and stillbirth during the COVID-19 pandemic in Sweden: a nationwide cohort study.   Ann Intern Med. Published online January 12, 2021. doi:10.7326/M20-6367PubMedGoogle Scholar
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    Research Letter
    Obstetrics and Gynecology
    May 12, 2021

    Perinatal Outcomes During the COVID-19 Pandemic in Ontario, Canada

    Author Affiliations
    • 1Department of Obstetrics and Gynaecology, St Michael’s Hospital, Unity Health Toronto, Toronto, Ontario, Canada
    • 2Li Ka Shing Knowledge Institute, St Michael’s Hospital, Toronto, Ontario, Canada
    • 3ICES, Toronto, Ontario, Canada
    • 4Department of Obstetrics and Gynaecology, Sinai Health System, Toronto, Ontario, Canada
    • 5Dalla Lana School of Public Health, Division of Biostatistics, University of Toronto, Toronto, Ontario, Canada
    • 6Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
    • 7Department of Surgery, University of Toronto, Toronto, Ontario, Canada
    • 8Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
    JAMA Netw Open. 2021;4(5):e2110104. doi:10.1001/jamanetworkopen.2021.10104
    Introduction

    Public health measures to control the COVID-19 pandemic may be associated with reduced risk of preterm birth (PTB).1,2 Conversely, avoidance of health care may be associated with increased risk of stillbirth.3 We evaluated rates of PTB and stillbirth during the first 6 months of the pandemic because previous studies conducted early in the pandemic have had inconsistent results.

    Methods

    We performed a population-based cohort study in Ontario, Canada, using linked databases at ICES (formerly Institute for Clinical Evaluative Sciences).4 Data use without consent is authorized under section 45 of Ontario’s Personal Health Information Protection Act; thus, review by a research ethics board was not required. We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting in epidemiology guideline.5

    In-hospital births at 20 weeks’ or more gestational age (GA) from March 15 to September 30, 2020 (pandemic group), were compared with corresponding calendar periods from 2015 to 2019 (historical group) (eFigure in the Supplement). Births were identified in the Mother-Baby Data Set derived from the Canadian Institute for Health Information Discharge Abstract Database. Maternal characteristics included age, parity, singleton vs multiple gestation, area-level income quintile, comorbidities, pregnancy conceived with assisted reproductive technology, and SARS-CoV-2 infection during pregnancy.

    PTB (live birth at <37 weeks’ GA) and stillbirths (intrauterine death at ≥20 weeks’ GA) were the primary outcomes. Secondary outcomes were extreme PTB (<28 weeks’ GA), very PTB (<32 weeks’ GA), severe small for GA (birth weight less than the fifth percentile for sex and GA), neonatal intensive care unit admission, and early (up to 7 days) and late (8-28 days) neonatal death.

    We used univariable and multivariable logistic regression models to examine the association between birth period (pandemic vs historical) and odds of each outcome. A generalized estimating equations approach was used to account for clustering at the level of birth institution. We assessed the effect of time spent in the pandemic by incorporating an interaction term between our exposure (pandemic vs historical birth) and number of weeks since March 15, 2020, for each PTB outcome. Analyses were performed using SAS Enterprise Guide statistical software version 7.15 (SAS Institute). Statistical tests were 2-sided, with α < .05 considered significant. Data analysis was performed from March 15 to September 30, 2020.

    Results

    A total of 67 747 births occurred during the pandemic period, and 348 633 births occurred during the historical period. There were no differences in baseline characteristics between groups. There was no difference in the proportion of PTBs (5103 [7.5%] vs 26 216 [7.5%] PTBs) or stillbirths (347 [0.5%] vs 1799 [0.5%] stillbirths) between the pandemic and historical groups. After multivariable analysis, the adjusted odds ratio (aOR) for PTB was 1.00 (95% CI, 0.97-1.03), and that for stillbirth was 0.99 (95% CI, 0.89-1.11) (Table). We observed a small but significant difference in very PTB (<32 weeks’ GA) in the 2 groups (4531 [1.3%] vs 807 [1.2%] very PTBs; OR, 0.89; 95% CI, 0.80-0.99), which persisted after multivariable adjustment (aOR, 0.91; 95% CI, 0.85-0.98). There were no differences in extreme PTB, severe small for GA, neonatal intensive care unit admission, or neonatal death. We found no significant association between time spent in the pandemic and any outcome.

    Discussion

    We found no differences in the overall risk of PTB, stillbirth, or other perinatal outcomes during the first 6 months of the COVID-19 pandemic. We observed a small reduction in PTB at less than 32 weeks’ GA, similar to Denmark and Ireland, where comparable strict lockdown measures were in effect.1,2 In contrast, no difference in PTB was observed in a population-based study in Sweden, where strict lockdown orders were not in effect.6

    Limitations of this study include the inability to evaluate out-of-hospital births; however, less than 3% of births in Ontario occur outside of hospitals. We could not evaluate for some factors that influence PTB risk, such as smoking. We did not evaluate the risk of PTB among women who experienced COVID-19 during pregnancy because this number was small.

    The COVID-19 pandemic first wave did not coincide with significant changes in overall PTB or stillbirth in Ontario. A small reduction in PTB at less than 32 weeks’ GA suggests that strict lockdown measures may have been associated with reduced risk in this subgroup.

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    Article Information

    Accepted for Publication: March 19, 2021.

    Published: May 12, 2021. doi:10.1001/jamanetworkopen.2021.10104

    Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Simpson AN et al. JAMA Network Open.

    Corresponding Author: Andrea N. Simpson, MD, MSc, Department of Obstetrics and Gynaecology, St Michael’s Hospital, Unity Health Toronto, 61 Queen St E, 5th Flr, Toronto, ON M5C 2T2, Canada (andrea.simpon@unityhealth.to).

    Author Contributions: Dr Simpson had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

    Concept and design: Simpson, Snelgrove, Sutradhar.

    Acquisition, analysis, or interpretation of data: All authors.

    Drafting of the manuscript: Simpson, Sutradhar.

    Critical revision of the manuscript for important intellectual content: Snelgrove, Sutradhar, Everett, Liu, Baxter.

    Statistical analysis: All authors.

    Obtained funding: Simpson, Baxter.

    Administrative, technical, or material support: Simpson, Baxter.

    Supervision: Sutradhar, Baxter.

    Conflict of Interest Disclosures: None reported.

    Funding/Support: This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). This study was conducted with grant funding from the John R. McArthur Endowment Research Grant, Department of Obstetrics and Gynaecology, University of Toronto, and from the Department of Obstetrics and Gynaecology, St Michael’s Hospital (start-up grant to Dr Simpson).

    Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

    Disclaimers: The analyses, conclusions, opinions, and statements expressed herein are solely those of the authors and do not reflect those of the funding or data sources; no endorsement by ICES or the MOHLTC is intended or should be inferred. Parts of this material are based on data and information compiled and provided by the Canadian Institute for Health Information and Ministry of Health & Long-Term Care. However, the conclusions, opinions, and statements expressed herein are solely those of the authors, and not of those bodies listed. No endorsement by these bodies is intended or should be inferred.

    Additional Information: The data set from this study is held securely in coded form at ICES. Although data sharing agreements prohibit ICES from making the data set publicly available, access may be granted to those who meet prespecified criteria for confidential access (http://www.ices.on.ca/DAS).

    References
    1.
    Hedermann  G, Hedley  PL, Baekvad-Hansen  M,  et al.  Danish premature birth rates during the COVID-19 lockdown.   Arch Dis Child Fetal Neonatal Ed 2021;106(1):93-95. doi:10.1136/archdischild-2020-319990PubMedGoogle ScholarCrossref
    2.
    Philip  RK, Purtill  H, Reidy  E,  et al.  Unprecedented reduction in births of very low birthweight (VLBW) and extremely low birthweight (ELBW) infants during the COVID-19 lockdown in Ireland: a ‘natural experiment’ allowing analysis of data from the prior two decades.   BMJ Glob Health. 2020;5(9):e003075. doi:10.1136/bmjgh-2020-003075PubMedGoogle Scholar
    3.
    Khalil  A, von Dadelszen  P, Draycott  T, Ugwumadu  A, O’Brien  P, Magee  L.  Change in the incidence of stillbirth and preterm delivery during the COVID-19 pandemic.   JAMA. 2020;324(7):705-706. doi:10.1001/jama.2020.12746PubMedGoogle ScholarCrossref
    4.
    Joseph  KS, Fahey  J; Canadian Perinatal Surveillance System.  Validation of perinatal data in the Discharge Abstract Database of the Canadian Institute for Health Information.   Chronic Dis Can. 2009;29(3):96-100. doi:10.24095/hpcdp.29.3.01PubMedGoogle ScholarCrossref
    5.
    Knottnerus  A, Tugwell  P.  STROBE—a checklist to Strengthen the Reporting of Observational Studies in Epidemiology.   J Clin Epidemiol. 2008;61(4):323. doi:10.1016/j.jclinepi.2007.11.006PubMedGoogle ScholarCrossref
    6.
    Pasternak  B, Neovius  M, Söderling  J,  et al.  Preterm birth and stillbirth during the COVID-19 pandemic in Sweden: a nationwide cohort study.   Ann Intern Med. Published online January 12, 2021. doi:10.7326/M20-6367PubMedGoogle Scholar
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