Pregnancy, fetal, and neonatal outcomes after a first booster dose of covid-19 vaccine during pregnancy in Ontario, Canada: population based, retrospective cohort study

Deshayne B Fell; Sheryll Dimanlig-Cruz; Eszter Török; Siri E Håberg; Annette K Regan; Jay S Kaufman; Robert W Platt; Christopher A Gravel; Liam Bruce; Prakesh S Shah; Kumanan Wilson; Ann E Sprague; Gillian D Alton; Tavleen Dhinsa; Darine El-Chaâr; Sarah A Buchan; Jeffrey C Kwong; Sarah E Wilson; Sandra I Dunn; Shannon E MacDonald; Jon Barrett; Nannette Okun; Mark C Walker

doi:10.1136/bmjmed-2023-000632

Pregnancy, fetal, and neonatal outcomes after a first booster dose of covid-19 vaccine during pregnancy in Ontario, Canada: population based, retrospective cohort study

BMJ Med. 2023 Jul 11;2(1):e000632. doi: 10.1136/bmjmed-2023-000632. eCollection 2023.

Authors

Deshayne B Fell^{1

2}, Sheryll Dimanlig-Cruz^{2

3

4}, Eszter Török^{2

3}, Siri E Håberg⁵, Annette K Regan^{6

7}, Jay S Kaufman⁸, Robert W Platt⁸, Christopher A Gravel^{1

8}, Liam Bruce³, Prakesh S Shah^{9

10

11

12}, Kumanan Wilson^{4

13

14}, Ann E Sprague^{2

3}, Gillian D Alton^{2

3}, Tavleen Dhinsa^{2

3}, Darine El-Chaâr^{1

4

15}, Sarah A Buchan^{16

17

18}, Jeffrey C Kwong^{16

17

18

19}, Sarah E Wilson^{16

17

18}, Sandra I Dunn^{2

3

20}, Shannon E MacDonald^{21

22

23}, Jon Barrett²⁴, Nannette Okun²⁵, Mark C Walker^{1

2

3

4

15}

Affiliations

¹ School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada.
² Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada.
³ Better Outcomes Registry and Network, Ottawa, ON, Canada.
⁴ Ottawa Hospital Research Institute, Clinical Epidemiology Program, Ottawa, ON, Canada.
⁵ Norwegian Institute of Public Health, Centre for Fertility and Health, Oslo, Norway.
⁶ School of Nursing and Health Professions, University of San Francisco, San Francisco, CA, USA.
⁷ Department of Epidemiology, University of California Los Angeles Fielding School of Public Health, Los Angeles, CA, USA.
⁸ Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, QC, Canada.
⁹ Department of Pediatrics, Mount Sinai Hospital, Toronto, ON, Canada.
¹⁰ Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
¹¹ Department of Pediatrics, Maternal-infant Care Research Centre, Mount Sinai Hospital, Toronto, ON, Canada.
¹² Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada.
¹³ Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
¹⁴ Bruyere Research Institute, Ottawa, ON, Canada.
¹⁵ Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, ON, Canada.
¹⁶ Public Health Ontario, Toronto, ON, Canada.
¹⁷ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
¹⁸ Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
¹⁹ Department of Family & Community Medicine, University of Toronto, Toronto, ON, Canada.
²⁰ School of Nursing, University of Ottawa, Ottawa, ON, Canada.
²¹ Faculty of Nursing, University of Alberta, Edmonton, AB, Canada.
²² School of Public Health, University of Alberta, Edmonton, AB, Canada.
²³ Department of Pediatrics, University of Calgary, Calgary, AB, Canada.
²⁴ Department of Obstetrics and Gynecology, McMaster University, Hamilton, ON, Canada.
²⁵ Department of Obstetrics and Gynaecology, University of Toronto, Toronto, ON, Canada.

Abstract

Objective: To assess risk of adverse pregnancy, fetal, and neonatal outcomes after a third dose (first booster dose) of covid-19 vaccine during pregnancy among individuals who had completed both doses of primary covid-19 vaccine series before pregnancy.

Design: Population based, retrospective cohort study.

Setting: Ontario, Canada, from 20 December 2021 to 31 August 2022.

Participants: Individuals were included if they were pregnant with an expected date of delivery from 20 December 2021 (start date of third dose eligibility for everyone ≥18 years) to 31 August 2022, who had completed the two doses of primary covid-19 messenger RNA vaccine series before pregnancy, and became eligible for a third dose (≥six months since dose two) before the end of pregnancy.

Main outcome measures: Pregnancy outcomes included hypertensive disorders of pregnancy, placental abruption, caesarean delivery, chorioamnionitis, and postpartum hemorrhage. Fetal and neonatal outcomes included stillbirth, preterm birth, admission to neonatal intensive care unit for >24 h, newborn 5 min Apgar score <7, and small-for-gestational age infant (<10th percentile). We estimated hazard ratios and 95% confidence intervals for study outcomes, treating dose three as a time varying exposure and adjusting for confounding using inverse probability weighting.

Results: Among 32 689 births, 18 491 (56.6%) were born to individuals who received a third covid-19 dose during pregnancy. Compared with eligible individuals who did not receive a third dose during pregnancy, no increased risks were associated with receiving a third covid-19 vaccine dose during pregnancy for placental abruption (adjusted hazard ratio 0.84 (95% confidence interval 0.70 to 1.02)), chorioamnionitis (0.67 (0.49 to 0.90)), postpartum haemorrhage (1.01 (0.89 to 1.16)), caesarean delivery (0.90 (0.87 to 0.94)), stillbirth (0.56 (0.39 to 0.81)), preterm birth (0.91 (0.84 to 0.99)), neonatal intensive care unit admission (0.96 (0.90 to 1.03)), 5 min Apgar score<7 (0.96 (0.82 to 1.14)), or small-for-gestational age infant (0.86 (0.79 to 0.93)).

Conclusion: Receipt of a third covid-19 vaccine dose during pregnancy was not associated with an increased risk of adverse pregnancy, fetal, or neonatal outcomes. These findings can help to inform evidence based decision making about the risks and benefits of covid-19 booster doses during pregnancy.

Keywords: COVID-19.