Pregnant women are exposed to many things that can activate her immune system. These can impact short and long-term health outcomes for the developing fetus. Viruses, bacteria, and non-maternal cells can activate the immune system. Let’s take a moment to appreciate how the body deals with these challenges.
From the very beginning of pregnancy, the immune system takes steps to avoid rejecting the embryo. If she doesn’t stop the immune system, it will detect the embryo and eliminate it. It is crucial to protect the embryo so that fetal development goes smoothly.
One of the important functions of the placenta is to limit the exchange of fetal and maternal cells, but it’s not 100%. Some types of fetal cells do cross the placental barrier, including red and white blood cells.
You may expect the mother’s body to eradicate fetal cells that enter her cells. After all, they contain foreign DNA from the biological father. But instead, these fetal cells can live in the bloodstream and tissues of the mother for decades! These fetal cells help the body heal and recover from birth, and they can integrate into many maternal tissues.
When we hear the term “immune suppression” – it sounds bad, right? But this is necessary and normal in the early stages of pregnancy to avoid rejecting the fetus. As pregnancy continues, other aspects of the immune system continue to adjust. Some experts even argue that it’s actually immune “modulation” instead of “suppression” – – Yet the fact remains that pregnant individuals are more susceptible to viral infections.
Viral infections trigger the maternal immune system. This results in inflammatory molecules that cross the placenta and can influence the pregnancy.
Many types of viral infections have been studied on this topic. For example, the human papilloma virus (HPV) can lead to placenta issues. This may be why obstetric complications are higher when HPV infections occur during pregnancy, such as miscarriage and pre-term delivery. Similar to the HPV infection, the 2009 H1N1 flu infected many pregnant women worldwide. The H1N1 infection increased pre-term deliveries and miscarriages.
Specific fetal tissues can be affected by in utero viral infections. For instance, the last rubella outbreak (1964) in the US caused over 11,000 miscarriages and more than 20,000 babies were born with birth defects. This is because rubella viral infections can alter heart development, causing newborns with congenital heart disease.
Many viruses pose a threat, but what about coronaviruses? The coronavirus that causes Severe Acute Respiratory Syndrome (SARS) circulated in the early 2000’s. When contracted during pregnancy, the SARS coronavirus caused fetal distress, growth restriction, and was associated with a higher risk of miscarriage. With these serious concerns about viral infection, it’s time to explore the research on the coronavirus we are dealing with today, COVID-19.
Studies confirm that when a pregnant woman is infected, the virus infects the placenta and amniotic fluid. (The specific receptor that binds the coronavirus spike protein is abundant in these tissues.) Unfortunately, pregnant women are more susceptible to severe COVID-19 symptoms compared to nonpregnant women.
Large-scale studies are finally available. Like many other viruses, COVID infection during pregnancy increases the risk of adverse birth outcomes. These include higher rates of pre-term delivery, low birth weight, and stillbirths. Many of these outcomes are only a small percentage higher, but this can have big health care impacts. About 5% of women of reproductive age in the general population are pregnant at any given time, so small percentages across millions of individuals does matter.
A study on infants born to mothers infected with COVID during pregnancy was first to report on developmental outcomes. “Being in the womb of a mother experiencing the pandemic was associated with slightly lower scores in areas such as motor and social skills, though not in others, such as communication or problem-solving skills. The results suggest that the huge amount of stress felt by pregnant mothers during these unprecedented times may have played a role.”
Research is underway to find out what outcomes are related to infection and what is the result of maternal stress. Anxiety and depression can contribute to pregnancy complications, and these stress-related conditions were both significantly elevated for pregnant women during the pandemic.
The COVID-19 vaccine causes the body to produce antibodies against the spike protein of the virus. These are detectable in the mother’s blood and umbilical cord at birth. CDC Director Dr. Walensky urges the vaccines based on safety data that shows they do not increase risk of miscarriage among pregnant woman.
The amount of antibodies relates to how much protection is conferred against COVID-19 infection. Compared to pregnant women who contract COVID, those who get vaccinated during pregnancy have “significantly greater antibody persistence in their infants.” The amount of antibodies may be over three times higher compared to those who were unvaccinated and infected. Vaccination offers a greater degree of protection to both the mother and her offspring.
In addition, the same study followed up on infants born to mothers either vaccinated against or infected with COVID-19 during pregnancy. By the time infants were 6 months old, almost 60% of the infants born to vaccinated mothers had detectable antibodies. In contrast, only 8% of infants born to infected mothers had detectable antibodies. We need more research, but this indicates vaccination offers far better protection than infection.
As Treo’s Global Wellness Researcher, Karlie uses recent research findings to support healthier daily habits. Karlie earned her doctorate in Neuroscience and Behavior and bachelors in Health and Exercise Science.
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