The Immunological Paradox of Pregnancy

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photo credit: Carmen Hibbins

For most women, navigating pregnancy is difficult. There are decisions to be made: maternity care, labor preferences, place of birth, newborn care, breastfeeding, etc. Not to mention vaccines. Currently the CDC recommends the influenza vaccine for all pregnant women. When making the decision to accept or decline the flu vaccine, it’s important to first understand a pregnant woman’s immune system, as well as the ingredients in different kinds of flu vaccines.

The immune system is a complicated system of cells, tissues, and lymphoid organs—a giant communication network. When cells receive alarms about antigens in the body (viruses, bacteria, parasites, fungi), they produce chemicals that seek to destroy the antigens ability to invade the body. Recently research has shown the importance of a healthy gut for a strong immune system – and for brain health. Really, we are only just beginning to understand the complexity of human immunity.

What we do know is that a woman’s immune system changes significantly from the moment of conception. The innate immune system, the immediate response part, is activated, which results in an increase in white blood cells (monocytes and granulocytes) and the pregnant woman’s production of natural killer (NK) cells decreases. Research has shown that a critical balance of immune cells as well the factors they produce are vital to a healthy pregnancy. Interfering with a pregnant woman’s immune responses is thought to have a negative effect, in particular in the early stages of the pregnancy. The decreased immunity and increase in white blood cells ensures implantation and the development of the placenta. Without it, the fetus can be rejected. Thus, the vast majority of vaccines aren’t indicated for pregnant women and they are generally avoided if possible.

The immunological paradox of pregnancy is complicated, delicate, and beautiful in the way only nature can be.

So what exactly are the risks and benefits of the flu vaccine? The benefit is easy to define: influenza poses a substantial risk for the pregnant woman, in particular during the later months of pregnancy. The woman’s altered immune state can leave her susceptible to certain infections and viruses, and when she contracts the flu it can be hard for her fight it. The CDC states:

Flu is more likely to cause severe illness in pregnant women than in women who are not pregnant. Changes in the immune system, heart, and lungs during pregnancy make pregnant women (and women up to two weeks postpartum) more prone to severe illness from flu, as well as to hospitalizations and even death. Pregnant women with flu also have a greater chance for serious problems for their developing baby, including premature labor and delivery.

The risks of influenza are real, despite the large number of women who have healthy, safe pregnancies without contracting the flu. So what about risks associated with the vaccine? Most of the research on vaccines is conducted on non-pregnant subjects, so researchers are careful to qualify results. The consensus tends to be: less vaccines overall for pregnant women, but the flu vaccine is indicated given the risks associated with the flu.

Current research focuses on the type of flu vaccines. Most flu vaccines are considered “non-adjuvanted.” An adjuvant is an additive used to increase the immune response to a vaccine. Adjuvant vaccines are important during pandemic times, as adjuvants allow more vaccines to be produced using less antigens and are therefore more cost effective. But adjuvants are pro-inflammatory and can aggravate other immune issues. Given the altered immune system of a pregnant woman, most researchers suggest that only non-adjuvanted flu vaccines be administered.

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The WHO organization issued the Safety of Immunization during Pregnancy report in 2014. The research is far from conclusive, but the WHO takes a careful look at results from studies around the world. In terms of the flu vaccine, they conclude:

Pregnant women and infants suffer disproportionately from severe outcomes of influenza. The effectiveness of influenza vaccine in pregnant women has been demonstrated, with transfer of maternally derived antibodies to the infant providing additional protection. The excellent and robust safety profile of multiple inactivated influenza vaccine preparations over many decades, and the potential complications of influenza disease during pregnancy, support WHO recommendations that pregnant women should be vaccinated. Ongoing clinical studies of the effectiveness, safety, and benefits of influenza vaccination in pregnant women in diverse settings will provide additional data that will aid countries in assessing influenza vaccine use for their own population.

If you’re pregnant, weigh the risks and benefits, and take into account any specific immunity issues. Is your immune system weakened for any reason? What is the risk of exposure? Do you tend to contract the flu? What is your family history in terms of vaccine reactions? Are you high risk for any other reason? Talk over the risks and benefits with your care provider. Ultimately, the decision is yours. Your pregnancy is your pregnancy, and a mother’s intuition is often the best guide.

If you choose to have the flu vaccine administered during your pregnancy, be sure that the vaccine is non-adjuvanted/inactivated. In the next blog post on Birth Outside the Box, we’ll discuss ways to naturally boost your immunity during pregnancy – ways to help you counteract the altered immune state that nature has carefully designed to ensure a successful pregnancy. Garlic? Diet? Sleep? Exercise? We’ll cover it all!

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One thought on “The Immunological Paradox of Pregnancy

  1. […] written in the past about a pregnant woman’s lowered immunity. Good nutrition, sanitation habits, rest, and exercise all help to strengthen the pregnant […]

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