Infections in the first trimester of pregnancy can be teratogenic, but the possibility that Covid-19 could lead to birth defects is unclear. We examined whether SARS-CoV-2 infection during pregnancy or exposure to pandemic conditions were associated with the risk of congenital anomalies. We carried out a retrospective study of 420,222 neonates born in Quebec, Canada in two time periods: prepandemic (January 1, 2017 to March 12, 2020) vs. pandemic (March 13, 2020 to March 31, 2022). We classified pandemic births as early (first trimester completed before the pandemic) or late (first trimester during the pandemic), and identified patients with SARS-CoV-2 infections during pregnancy. We applied (1) adjusted log-binomial regression models to assess the association between SARS-CoV-2 infection and congenital anomalies, and (2) autoregressive interrupted time series regression to analyze temporal trends in the monthly number of defects in all patients regardless of infection. In total, 29,263 newborns (7.0%) had a congenital anomaly. First trimester SARS-CoV-2 infections were not associated with a greater risk of birth defects compared with no infection (RR 1.07, 95% CI 0.59–1.95). However, births during the late pandemic period were more likely to be diagnosed with congenital microcephaly compared with prepandemic births (RR 1.44, 95% CI 1.21–1.71). Interrupted time series analysis confirmed that the frequency of microcephaly increased during the late pandemic period, whereas other anomalies did not. We conclude that Covid-19 is likely not teratogenic, but enhanced surveillance of anomalies among late pandemic births may have heightened the detection of infants with microcephaly.

怀孕前三个月的感染可能会致畸，但 Covid-19 导致出生缺陷的可能性尚不清楚。我们研究了怀孕期间感染 SARS-CoV-2 或接触大流行病是否与先天异常风险相关。我们对加拿大魁北克省出生的 420,222 名新生儿进行了回顾性研究，分为两个时期：大流行前（2017 年 1 月 1 日至 2020 年 3 月 12 日）与大流行期间（2020 年 3 月 13 日至 2022 年 3 月 31 日）。我们将大流行出生分为早期（大流行前三个月）或晚期（大流行期间的前三个月），并确定了怀孕期间感染 SARS-CoV-2 的患者。我们应用（1）调整对数二项式回归模型来评估 SARS-CoV-2 感染与先天性异常之间的关联，以及（2）自回归中断时间序列回归来分析所有患者每月缺陷数量的时间趋势，无论其情况如何感染。总共有 29,263 名新生儿 (7.0%) 患有先天性异常。与未感染相比，妊娠早期 SARS-CoV-2 感染与出生缺陷风险增加无关（RR 1.07，95% CI 0.59-1.95）。然而，与大流行前的出生相比，大流行后期的出生更有可能被诊断为先天性小头畸形（RR 1.44，95% CI 1.21-1.71）。中断时间序列分析证实，小头畸形的发生率在大流行后期有所增加，而其他异常现象则没有增加。我们的结论是，Covid-19 可能不会致畸，但加强对大流行晚期出生异常的监测可能提高了小头畸形婴儿的检出率。