A study published by Piekos and others in The Lancet, January 13th 2022 discusses this issue. 

The impact of maternal SARS-CoV-2 infection remains unclear.  In their study, the authors evaluated the risk of maternal SARS-CoV-2 infection on birth outcomes and how this is modulated by the pregnancy trimester in which the infection occurred.

They also developed models to predict gestational age at delivery for people following a SARS-CoV-2 infection during pregnancy.

The authors performed a retrospective cohort study of the impact of maternal SARS-CoV-2 infection on birth outcomes.  They used clinical data from Providence St Joseph Health electronic health records for pregnant women who delivered in the USA at the Providence, Swedish, or Kadlec sites in Alaska, California, Montana, Oregon, or Washington.  

The SARS-CoV-2 positive cohort included patients who had a positive SARS-CoV-2 PCR-based test during pregnancy, subdivided by trimester of infection.  

No one in this cohort had been vaccinated for COVID-19 at time of infection.  The SARS-CoV-2 negative cohort were people with at least one negative SARS-CoV-2 PCR-based test and no positive tests during pregnancy.  

Cohorts were matched on common covariates impacting birth outcomes, and univariate and multivariate analysis were done to investigate risk factors and predict outcomes.  The primary outcome was gestational age at delivery with annotation of preterm birth classification.

Between March 5, 2020 and July 4, 2021, 73666 pregnant people delivered.  18335 of whom had at least one SARS-CoV-2 test during pregnancy before February 14, 2021. 

They observed 882 people infected with SARS-CoV-2 during their pregnancy their list, first trimester 85, second trimester 226 and third trimester 571 and 19769 people who have never tested positive for SARS-CoV-2 and received at least one negative SARS-CoV-2 test during their pregnancy.

SARS-CoV-2 infection indicated an increased risk of preterm delivery and stillbirth, accounted for primarily by first and second trimester SARS-CoV-2 infection.

Gestational age at SARS-CoV-2 infection was correlated with gestational age at delivery and had the greatest impact on predicting gestational age at delivery.  The people in this study had mild or moderate SARS-CoV-2 infections and acute COVID-19 severity was not correlated with gestational age delivery.

The results suggested that pregnant people would benefit from increased monitoring and enhanced prenatal care after first or second trimester SARS-CoV-2 infection regardless of acute COVID-19 severity.

  • Firstly, more negative birth outcomes were observed when infections occurred earlier in gestation including increased risk for preterm birth and stillbirth.  
  • Second, there were increased rates of SGA infants born to people who had a positive SARS-CoV-2 test result during pregnancy, suggesting a preterm delivery is induced via a mechanism that could impact foetal growth. 
  • Third, there appeared to be two distinct populations of pregnant people: A subset with a negative correlation between the time of maternal SARS-CoV-2 infection and gestational age at delivery and a second population appearing to be unaffected. 
  • Fourth, the difference between mild and moderate severity of the SARS-CoV-2 infection did not appear to play a part in whether a pregnancy is likely to be negatively affected.  

Taken together, these findings suggest that SARS-CoV-2 infection early in pregnancy is an important risk factor that should be monitored closely.

The potential mechanism, which could account for worse outcomes with 

SARS-CoV-2 infections earlier in gestation is thought to be an increased levels of angiotensin converting enzyme 2 (ACE2) in the placenta earlier in gestation.

The London General Practice commends the National Health Service on its vaccination program and encourage just all those eligible to be vaccinated and boosted.  In particular, it encourages those who are considering conception or pregnant to be vaccinated. 

The London General Practice provides a full screening service and monitoring services for all those with COVID or consideration of having COVID.

Dr Paul Ettlinger

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