Objective To assess the risk of preterm birth, small for gestational age at birth, and stillbirth after covid-19 vaccination during pregnancy. Design Population based retrospective cohort study. Setting Ontario, Canada, 1 May to 31 December 2021. Participants All liveborn and stillborn infants from pregnancies conceived at least 42 weeks before the end of the study period and with gestational age ≥20 weeks or birth weight ≥500 g. Main outcome measures Using Cox regression, hazard ratios and 95% confidence intervals were estimated for preterm birth before 37 weeks (overall and spontaneous preterm birth), very preterm birth (<32 weeks), small for gestational age at birth (<10th centile), and stillbirth. Vaccination against covid-19 was treated as a time varying exposure in the outcome specific risk window, and propensity score weighting was used to adjust hazard ratios for potential confounding. Results Among 85 162 births, 43 099 (50.6%) occurred in individuals who received one dose or more of a covid-19 vaccine during pregnancy—42 979 (99.7%) received an mRNA vaccine. Vaccination during pregnancy was not associated with any increased risk of overall preterm birth (6.5% among vaccinated v 6.9% among unvaccinated; adjusted hazard ratio 1.02, 95% confidence interval 0.96 to 1.08), spontaneous preterm birth (3.7% v 4.4%; 0.96, 0.90 to 1.03), or very preterm birth (0.59% v 0.89%; 0.80, 0.67 to 0.95). No increase was found in risk of small for gestational age at birth (9.1% v 9.2%; 0.98, 0.93 to 1.03) or stillbirth (0.25% v 0.44%; 0.65, 0.51 to 0.84). Findings were similar by trimester of vaccination, mRNA vaccine product, and number of doses received during pregnancy. Conclusion The findings suggest that vaccination against covid-19 during pregnancy is not associated with a higher risk of preterm birth, small for gestational age at birth, or stillbirth. The dataset from this study is held securely by BORN Ontario. Although the dataset cannot be made publicly available, the analytical code may be available on request.

中文翻译：

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怀孕期间接种 covid-19 疫苗后的早产、出生时小于胎龄和死产的风险：基于人群的回顾性队列研究


目的 评估妊娠期间接种 Covid-19 疫苗后发生早产、出生小于胎龄和死产的风险。设计基于人群的回顾性队列研究。地点：加拿大安大略省，2021 年 5 月 1 日至 12 月 31 日。 参与者 所有在研究期结束前至少 42 周受孕且胎龄≥20 周或出生体重≥500 克的活产和死产婴儿。主要结局指标 使用 Cox 回归，估计 37 周前早产（总体早产和自发早产）、极早产（<32 周）、出生时小于胎龄（<10 个百分位）的风险比和 95% 置信区间和死产。针对 covid-19 的疫苗接种被视为结果特定风险窗口中随时间变化的暴露，并使用倾向评分加权来调整潜在混杂因素的风险比。结果 在 85 162 例新生儿中，有 43 099 例（50.6%）在怀孕期间接受了一剂或多剂 covid-19 疫苗，而 42 979 例（99.7%）则接种了 mRNA 疫苗。怀孕期间接种疫苗与总体早产风险增加无关（已接种疫苗的为 6.5%，未接种疫苗的为 6.9%；调整后的风险比为 1.02，95% 置信区间为 0.96 至 1.08）、自发性早产（3.7% vs 4.4%；0.96） ，0.90 至 1.03），或极早产（0.59% vs 0.89%；0.80、0.67 至 0.95）。出生时小于胎龄儿（9.1% vs 9.2%；0.98、0.93 至 1.03）或死产（0.25% vs 0.44%；0.65、0.51 至 0.84）的风险没有增加。疫苗接种三个月期、mRNA 疫苗产品以及怀孕期间接受的剂量数量的结果相似。 结论 研究结果表明，怀孕期间接种 covid-19 疫苗与早产、出生小于胎龄或死产的较高风险无关。本研究的数据集由 BORN Ontario 安全保存。尽管数据集无法公开，但可以根据要求提供分析代码。