Newborn Babies Can Receive COVID-19 Antibodies From Mothers While in Utero, According to New Penn Study

Penn researchers have studied newborn babies COVID antibodies they receive from their mothers in utero. Photograph by Yasser Chalid/Getty Images

Since the start of the pandemic, very little research on COVID-19 has accounted for pregnant individuals. As of last June, less than two percent of approximately 900 global coronavirus studies and clinical trials related to pregnancy. This is likely due to the fact that pregnancy is considered a medical condition that typically excludes pregnant individuals from participating in clinical trials due to neonatal safety concerns. In turn, though, leaving out pregnant mothers from such research doesn’t provide them with any insight into potential risks a novel, highly transmissible virus could have on their own health and that of their baby.

This lack of information regarding maternal and fetal health in the age of coronavirus is what recently led one group of Penn researchers to conduct a study on antibody placental transfer. Their goal: determine the extent to which SARS-CoV-2 antibodies pass from woman to fetus during pregnancy. That way, doctors and patients alike might have a better sense of how to navigate infant care in light of maternal infection. From April 9th to August 8th at Pennsylvania Hospital, the team tested blood samples from 1,471 women and their newborn’s cord blood for SARS-CoV-2 antibody measurement. They discovered that, out of 83 seropositive mothers, 72 newborns showed high concentrations of SARS-CoV-2 antibodies in their cord blood. Though the CDC says it is still unclear how much protection SARS-CoV-2 antibodies may provide or how long that protection might last, the Penn findings are promising for neonatology’s journey toward protecting fetuses and newborns against COVID-19.

To get a fuller understanding of the research and results, we spoke with co-senior author Karen Puopolo, who is a neonatologist at CHOP, an associate professor of pediatrics at the Penn’s Perelman School of Medicine, and the chief of the section on newborn medicine at Pennsylvania Hospital. Below, Puopolo discusses motivations behind this kind of study, as well as what the findings mean for pregnant individuals at this stage of the pandemic and beyond.

NextHealth: Why did you and your co-authors initiate a study like this?
Puopolo: Because SARS-CoV-2 is a novel virus, researchers have needed to ask questions that boil down to, “How might this specific thing be impacted by COVID-19?” In my field, pregnant individuals can often be exposed to various infections during pregnancy, but most of the time, those infections aren’t too serious, mainly because the mother has built up immunological memory throughout their lifetime. Although newborns come into the world with a simplistic immune system that develops over time, antibodies to infections, specifically Immunoglobulin G (IgG), are pumped across the mother’s placenta to the fetus, providing newborns some defenses against the world they’re entering into. With that said, though, very little research has been done on maternal and fetal immune responses to COVID-19, so our team wanted to find out for certain the extent to which antibodies to SARS-CoV-2 could be transferred from mother to child.

If antibodies to other viruses often transfer, though, wouldn’t antibodies to SARS-2 simply do the same?
People develop antibodies to infections differently, especially because each person’s acquired immune system changes throughout their life. Also, the amount or degree of antibodies that actually cross through the placenta can vary from one pregnancy to the next. For those reasons, we couldn’t safely assume that a similar placental transfer would happen with SARS-CoV-2 antibodies.

What research questions did you seek to answer with this study?
Fundamentally, we asked, “Does being sick with COVID-19 while pregnant interfere with placental transfer?” Sure, a mother can and does pass along antibodies to the fetus, but oftentimes, the mother does so when she isn’t battling a novel virus. With so much still unknown about the relationship between pregnancy and COVID-19, we knew we needed to try to uncover answers about a mother’s ability to pass antibodies after becoming symptomatic while carrying.

We were also interested in the timeframe between developing SARS-CoV-2 antibodies and delivery, and how that span might impact the level of antibodies transferred.

What key findings did you and your team discover?
Of the 1,471 maternal blood samples we tested, 83 contained SARS-CoV-2 IgG antibodies at the time of delivery, and IgG antibodies were detected in [newborn] cord blood of 72 of those 83. That means the majority of seropositive mothers transferred significant levels of SARS-CoV-2 IgG antibodies to their newborns. No infants who were seropositive were born to the 1,388 seronegative women.

As I mentioned, we were curious about the timeframe between maternal infection and neonatal antibodies. We found that if COVID-19 develops in the mother at least two to three weeks prior to delivery, SARS-CoV-2 antibodies were present in the baby. Also, we discovered that antibody transfer ratios were associated with the time elapsed from infection. In other words, a greater amount of antibodies were detected as the time window between maternal infection and delivery increased. Overall, this means the mother is building up SARS-CoV-2 antibodies at high concentrations — especially when the duration between infection onset and delivery time is longer — and that the placenta is working very well to quickly and efficiently transfer built-up antibodies.

Additionally, we did not detect any IgM antibodies [a larger class of antibodies] in any cord blood sample, which suggests to us that the virus itself had neither crossed the placenta, nor infected the newborns.

Can this tell us anything about vaccinating pregnant individuals?
While most COVID-19 vaccines are generally designed to elicit high levels of IgG antibodies, our findings can’t comment on the amount of protection vaccines might provide to mother or child. We see our study as a starting point, so that vaccine researchers and developers can begin determining when or if to vaccinate those who are or are actively trying to become pregnant.

Why are these findings important at this point in the pandemic?
Healthcare of the 21st century, especially here in the United States, infrequently faces something it knows little about because we’ve come to know and discover so much. But this past year has been a humbling reminder of how hard it is to face a new virus — one that is extremely transmissible, one that has killed so many folks in such a short amount of time. It’s why people need a stronger understanding of how COVID-19 can impact various facets of life. In our case, we’re doing everything we can to learn more about that impact, so we can counsel and take care of mothers and their babies in this “new normal.”

I think our findings should give hope to folks who are pregnant or will become pregnant as the pandemic continues. Pregnancy can be stressful and overwhelming without a global pandemic going on, and we want to mitigate the negative feelings and uncertainties that surround the way COVID-19 might affect mothers and their babies. Take, for instance, a mother holding their newborn following delivery. It’s a special and necessary moment that promotes bonding between them. If a pregnant mother has active chicken pox or tuberculosis at the time of delivery, however, doctors will immediately separate mother and child because the newborn’s antibodies haven’t had time to develop, which could be life-threatening up against those infections. That separation can be devastating for the mother. But if the mother was sick months before [delivery] and is not symptomatic, they don’t need to worry about their baby being taken away because they’ve had time to build up antibodies — ones that will transfer to their child through the placenta. In a similar vein, our research has helped build confidence in not needing to separate if the mother is sick with COVID-19 at the time of delivery. If a mother is sick at the time of delivery, there will be more risk [than if she is not], but it is not cause for separation. That’s a huge relief for both mothers and doctors.