Tanzina Vega: For many people, pregnancy and childbirth are already incredibly stressful, but during a once-in-a-generation pandemic, it certainly raises that stress level, especially since pregnant people have a higher chance of developing more severe cases of the Coronavirus. I know this both as a journalist and as someone who had a kid during the pandemic. I gave birth in July and my son is now 10 months old.

For a lot of us, the news of vaccines being distributed felt like such a weight being lifted, but for some pregnant people, it also raised questions as to what that could mean for their health and the health of their fetus. The silver lining for many of us is that some of the studies have shown that vaccinated pregnant people are able to pass antibodies on to their babies.

Today in the US, more than 100,000 pregnant people have been vaccinated. Joining me now to help break all of this down is Dr. Kathryn Gray, associate obstetrician at Brigham and Women's Hospital and assistant professor at Harvard Medical School. Dr. Gray, welcome to The Takeaway.

Dr. Kathryn Gray: Thank you.

Tanzina Vega: Let's lay out the official CDC guidance when it comes to people who are pregnant or breastfeeding, getting the COVID-19 vaccine.

Dr. Kathryn Gray: This has been evolving over time as more evidence has come out, but the basic party line has still been that this is a discussion between the provider and the patient about the vaccine, so weighing the risks and the benefits. Thankfully, with time since the vaccine has come out, we have found that so far, it looks like the COVID vaccines are safe in pregnancy.

Through their CDC pregnancy registry, there's been no safety signals, so no increased rate of miscarriage, no increased rate of preterm birth, or any other complications that have been detected. Through many studies that have come out now, including ours, we have seen that pregnant women respond similarly as non-pregnant women to the vaccines, so they mount a good antibody response, and they also are able to pass antibodies through the placenta to the baby and through their breast milk. When discussing it, like you mentioned, pregnant patients are at increased risk of getting severe COVID, and they have the ability to be protected themselves and to protect their neonates by getting the vaccine. Those are points that we discuss with patients.

Tanzina Vega: What kind of questions do your patients ask you, and what do you tell them?

Dr. Kathryn Gray: There's been a lot of concern about the safety piece. What do we know about safety? Could there be things that we haven't been able to detect because this is so new? People are concerned about the lack of time since the vaccine has been available. They want to know what degree of protection it will have for them. If they've had COVID before, should they get the vaccine, or are they already protected? They're very concerned about what level of protection their baby will have if they get vaccinated and breastfeed, which we're still working on getting data on. We think there should be some protection from pregnant patients being vaccinated to their neonates, but we don't know how much yet, so patients really want to know that.

Tanzina Vega: In terms of the research, what does it tell us so far about how these vaccines interact with fetal development?

Dr. Kathryn Gray: We don't know of any adverse effects on fetal development. From what we know about other vaccines, we know that vaccines, over time, all the ones we have studied are very safe in pregnancy, and actually, some vaccines are--

Tanzina Vega: And recommended.

Dr. Kathryn Gray: Yes. Pertussis, or the whooping cough, vaccine is recommended at 28 weeks of pregnancy, and that's because moms generate antibodies that do pass to the baby and prevent very young infants from getting whooping cough, and it's really important. Same with influenza. We know pregnant women get sicker from influenza than non-pregnant individuals. It's recommended if you are pregnant during the flu season to get the flu vaccine.

Tanzina Vega: Dr. Gray, have there been trials that focus specifically on how pregnant people react to these vaccines?

Dr. Kathryn Gray: The only clinical trial that is being done that I'm aware of right now in the United States is the Pfizer vaccine, and that started at the end of February. They're gathering data on safety and effectiveness of the vaccine in pregnant patients. Then there's just the registry about safety, and then many studies coming out of academic centers that are looking at side effects from the vaccine in pregnant patients and efficacy.

Tanzina Vega: One of the things that I find completely fascinating and did when I was pregnant, and then when I had a newborn was how immunity works between mother and baby. I'd love for you to explain how immunity and antibodies from vaccines are passed on to babies.

Dr. Kathryn Gray: Sure. I think there's two things to think about. One is how antibodies are passed during pregnancy from mom to the fetus, and then how antibodies are passed during breastfeeding from mom to the baby. During pregnancy, when mother receives a vaccine, the pregnant individual mounts an immune response, so mom generates antibodies, then certain types of those antibodies, which we refer to as IgGs can pass through the placenta into the baby's blood, and provide what we call passive immunity. When the baby is born, those antibodies from mom stay in the baby's blood for several months and help provide protection.

In breastfeeding, there's antibodies that are also secreted in the breast milk from mom. Those, obviously, the baby ingest into the GI tract, and we know those provide some protection within the GI tract. What other immune responses those antibodies might provoke in the infant are a subject of great investigation and interest. I think we don't have a full understanding of the degree of protection the breast milk and breastfeeding piece provide specifically.

Tanzina Vega: Yes, you're leading me toward my next question, which is what my group chats with other moms are aflame with which is, "If I am vaccinated and breastfeeding, am I passing some immunity on to my kid?"

Dr. Kathryn Gray: Yes. We think that there should be some protective effect. How much is just unknown at this point, and I wish we could answer that. We have had many inquiries from moms asking if they give their other older children breast milk, will they be able to confer some protection to those older children. We just don't know the degree of protection that that might provide, and I emphasize that regardless of vaccination of the mom during pregnancy or breastfeeding that as soon as vaccines are available to younger children in all age groups that they should still pursue vaccination.

Tanzina Vega: One thing that I think people who have not been pregnant or aren't pregnant may not have thought about a lot is how little information there can be on drugs in general, and how they affect pregnant people because doing those trials are hard. Can you explain the science and the ethics behind doing drug and vaccine research on pregnant people?

Dr. Kathryn Gray: Yes, this is a great area of controversy and a great area of need. I recently wrote an editorial discussing this topic, but when we leave pregnant patients out of trials on medications, it means that we don't have any evidence of how those drugs work during pregnancy when we know the metabolism and pharmacology is very different of medications than in non-pregnant individuals.

When we don't include women in trials, then we don't know how drugs behave in pregnancy. That poses a real problem because then the only data we have is people who received the drug during pregnancy, and we have to wait a long time to gather enough retrospective data to try to take a look at that. Inherently, that data is different and confounded in a way that prospective clinical trials are not.

We've really limited the ability of pregnant patients to make decisions about medications and other therapies and vaccines when we exclude them from trials, but you're right, that it does cost a lot of money, and you specifically have to recruit pregnant populations. There are concerns about fetal development and effects of medication on fetal development, some more than others, so it's a delicate balance between-- Protection by exclusion isn't always the best. With the COVID-19 vaccine, when it first came out, there were about 35,000 healthcare workers in the United States who were pregnant who were immediately eligible for the vaccine and there was no data, just left a lot of people without knowing what to do.

Tanzina Vega: What do you think causes that? Is it sexism? Is it cautiousness? What is it?

Dr. Kathryn Gray: One, over time, we haven't devoted as many resources towards women's health and pregnancy as we have other areas of research. Number two, there's this concern for fetal development over the concern for women's health or this delicate balance. I think people are hesitant and nervous about potential adverse outcomes for pregnant patients. It's tricky to figure out how one should approach this.

Tanzina Vega: There's also been some fear-mongering around vaccines and the effects on fertility. For people who are thinking about becoming pregnant, what does the data say about the effects of these vaccines on fertility?

Dr. Kathryn Gray: There's no evidence that the COVID-19 vaccines affect fertility and this is a rampant rumor that really took off in social media especially. I think it's really unfortunate because we've scared a lot of individuals away from being vaccinated and there is not any evidence or even plausible biologic pathways by which the vaccine could cause infertility. I would just tell people that this isn't based on any evidence that we know.

Tanzina Vega: Dr. Katherine Gray is an associate obstetrician at Brigham and Women's Hospital and assistant professor at Harvard Medical School. Thank you very much.

Dr. Kathryn Gray: Thank you.

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