COVID-19 Antibody Screening in Pregnancy

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes Coronavirus Disease 2019 (COVID19), which has been associated with mortality and morbidity in pregnant women. Nearly all COVID-19 patients produce antiviral immunoglobulin G (IgG) approximately 10–20 days after symptoms begin. However, the clinical importance of antibody testing, especially for pregnant patients, has not been fully explained. There are several methods for detecting antibodies to SARS-CoV-2. The three most commonly used methods are IgM and IgG titers, which are tested using either Chemiluminescence Immunoassay (CLIA) or Enzyme-Linked Immunosorbent Assay (ELISA) and the Rapid IgM-IgG combined antibody test. The advantages of these tests include:

Identification of “healed” women who were not tested before

Antibody screening would be advantageous since some results such as IgG positive can show immunity. The detection of antibodies to SARS-CoV-2 would mean the individual has been infected and is believed to be immune. Assuming they are protected against reinfection, some governments have suggested giving “immunity passports” or “risk-free certificates” to these patients so that they can return to work or travel.

Identification of infected women and women who are still at risk (eg, IgM and IgG negative)

A study published by the US Centers for Disease Control and Prevention showed that pregnant women are at increased risk of facing severe coronavirus symptoms. Compared to non-pregnant women, pregnant women with COVID-19 are 50% more likely to require intensive care and 70% more likely to use mechanical ventilators, although the risk of death is not higher. Therefore, patients must be tested before admission to prevent contagion and receive treatment accordingly.

Usage in studies- Vaccination might protect infants too

Maternally produced antibodies are an important component of newborn immunity. Understanding the dynamics of maternal antibody responses to SARS-CoV-2 infection throughout pregnancy and subsequent transplacental antibody transfer might help improve treatment as well as vaccination strategies.

The researchers at the University of Pennsylvania’s Perelman School of Medicine routinely screened women for SARS-CoV-2 by nasopharyngeal polymerase chain reaction (NP-PCR) testing. They collected maternal and cord blood serum for study purposes to investigate the relationship between maternal and newborn SARS-CoV-2 antibody concentrations. It was concluded that antibodies against the SARS-CoV-2 coronavirus in the blood of pregnant women cross the placenta efficiently and are found in similar quantities in the blood of their babies.

Researchers tested blood samples of 1,471 women and their newborns and found that 83 of them had significant levels of SARS-CoV-2 specific antibodies. 87% of the newborns also had these antibodies, meaning antibodies crossed the placenta from the mother’s blood to the fetal circulation since there was no evidence of fetal infection. Unlike immunoglobulin G (IgG), IgM antibodies (which are produced earlier in infection) can not cross the placenta. So, their absence in the infant’s blood meant the virus had not infected them.

In conclusion, there are many benefits of antibody screening for pregnant women, so it is recommended that it be done before receiving care.
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References: Zullo, F., Di Mascio, D., & Saccone, G. (2020). COVID-19 Antibody Testing in Pregnancy. American Journal of Obstetrics & Gynecology MFM, 100142. doi:10.1016/j.ajogmf.2020.100142
Lapid, N. (2020). Antibody test accuracy unclear; COVID-19 risks higher for pregnant women. Reuters.
Flannery, D.D., Gouma, S., Dhudasia, M.B., et al. (2021). Assessment of Maternal and Neonatal Cord Blood SARS-CoV-2 Antibodies and Placental Transfer Ratios. JAMA Pediatr;175(6):594–600. doi:10.1001/jamapediatrics.2021.0038 – Penn Medicine News. (2021). Pregnant Mothers’ Antibodies to SARS-CoV-2 Transfer Efficiently to their Fetuses.