How Does Pregnancy Affect Your Immune System?

Your body goes through many changes during pregnancy, including complex changes to the immune system. The immune system plays an important role in protecting you from infection and illness. And pregnancy likely makes parts of your immune system even stronger. But it isn’t quite that simple. Being pregnant can also increase your risk of having certain infections and can make normally mild infections more severe. 

There’s ongoing research about why and how these changes in the immune system happen. One thing is for sure, it’s much more complex than researchers previously thought. The immune system isn’t suppressed in pregnancy but is hyperalert in different ways. Read on to learn more about how your immune system changes during pregnancy — and what this means for a healthy pregnancy. 

How does the immune system work? 

Your immune system is designed to protect your body from harm and help it heal from infections, injuries, and foreign bodies. The immune system also helps your body remember previous infections so it can better fight them next time. 

The immune system is complex, with many layers of communication. At the most basic level, it identifies which cells are your own and which cells are foreign. The immune system cells will quickly identify cells that are foreign and work to destroy them.

There are two main parts of the immune system:

1. Innate (natural) immunity is the part of the immune system that reacts quickly to a threat. It’s what works in the first hours and days of an infection. Innate immunity involves white blood cells (including neutrophils, eosinophils, macrophages, and dendritic cells) and inflammatory chemicals (cytokines).

2. Adaptive (acquired) immunity is when the immune system targets specific threats. It involves immune cells (like T and B cells). These cells develop antibodies that quickly identify intruders. Adaptive immunity takes more time but can provide a stronger defense.

Sometimes the immune system doesn’t work appropriately and attacks its own cells. This can lead to autoimmune disease. 

Is your immune system stronger or weaker when you’re pregnant?

Your immune system changes a lot during pregnancy. It’s possible some parts of your immune system ramp up, while others slow down. But in reality, it’s probably much more complex than we know. 

Some parts of the innate immune system can get stronger during pregnancy, making the initial defense from infection better. For example, cervical mucus (“mucus plug”) increases, which helps protect the uterus from infection. 

At the same time, some parts of adaptive immunity may decrease during pregnancy. This helps prevent immune cells from identifying the fetus as an “intruder,” but it may mean immune cells can’t fight some infections as well as usual. 

Pregnancy means an increased risk of some infections — such as COVID-19 and influenza — both because of immune changes as well as some of the physical changes of pregnancy.

When does your immune system change during pregnancy?

Your immune system starts to change at the beginning of pregnancy. This is because when the embryo implants, the immune system has to adapt so that it doesn’t identify the fetus as an intruder. The maternal immune system has to change to protect the growing fetus.

How long does it take your immune system to recover after pregnancy?

Your immune system should be back to normal about 3 to 4 months after pregnancy and birth. 

Does pregnancy make you more susceptible to certain health issues?

Yes, pregnancy can increase the risk of certain infections as it leads to changes in the immune system. And pregnancy also causes other physical changes in the body, which can increase risk for infections:

• There’s more pressure on the bladder and increased risk of urinary tract infections (UTIs). 

• There’s increased fluid and pressure in the lungs and increased risk of serious lung infections (pneumonia).

• Increased weight and fluid put more strain on the heart.

• Hormonal changes can lead to vaginal changes, including bacterial vaginosis or yeast infections. 

Some infections can also be more serious for a pregnant mother or fetus. COVID-19, for example, can be more serious in pregnancy.

Does pregnancy cause inflammation?

Yes, being pregnant can cause inflammation. In fact, even in healthy pregnancies, it’s normal to have a raised white blood cell count and C-reactive protein (both markers of inflammation). 

But too much inflammation may cause problems for both mother and baby, including an increased risk of asthma or allergies in childhood.

Some medical conditions and health behaviors may make it more likely to have levels of inflammation that are higher than normal during pregnancy, including:

• Higher body mass index (BMI)

• Dietary factors, such as a diet high in sugars, trans fats, and saturated fats 

• Preeclampsia

• Gestational diabetes

• Antibiotic use

• Smoking 

How can you improve your immune system during pregnancy?

People in good health don’t need to panic — if you take care of your body and follow standard recommendations during pregnancy, your body knows how to do the rest. 

You may be able to find ways to help support your immune function during pregnancy (and beyond) with some lifestyle habits, including:

• Lowering sugar and foods with high glycemic index

• Increasing your fruit and vegetable intake

• Decreasing saturated and trans fats

• Increasing fiber

• Exercising regularly

• Getting enough omega-3 fats

• Being up to date on recommended vaccines

Be sure to review your diet and supplements with your healthcare provider, especially during pregnancy. 

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Written by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a special interest in chronic care management, women’s health, mental health, and preventive care. She has over 10 years of experience in primary care research, innovation, and practice.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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