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Pregnancy & The Immune System: Remarkable Adaptations Explained

Friday 21 Oct 2022
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Pregnancy is a miraculous journey, marked not just by the growth of a new life but also by the incredible adaptability of the mother’s body. One of the most awe-inspiring aspects is how the immune system, designed to protect us from foreign invaders, allows a baby with 50% foreign DNA to grow.

 With tools like our advanced due date calculator, we can predict the timeline of the pregnancy journey, but understanding the science behind it offers a deeper appreciation.

The Immune System’s Protective Role

Our immune system is a vigilant guardian, attacking foreign organisms, tissues, and germs to shield us. This protective nature poses a question: How does a baby, with half of its DNA being foreign, grow inside its mother without being rejected?

Complexities of the Immune Response

The immune system, one of our body’s most intricate systems, defends us from potentially harmful invaders using a network of immune cells. Typically, any foreign tissue triggers an aggressive immune response aimed at eliminating the intruder1. However, during pregnancy, this system undergoes a “reprogramming” to accommodate the fetus while still defending against genuine threats like viruses and bacteria.2,3

Reciprocal Tolerance: A Two-Way Street

A successful pregnancy isn’t just about the mother’s cells tolerating the baby. The baby’s immune response, though still developing, also has to recognize and accept maternal cells.3 This mutual tolerance is crucial for a complication-free pregnancy.

The Placenta: Bridging Two Immune Systems

The placenta, a unique organ present only during pregnancy, is pivotal in the cooperation between the maternal and fetal immune systems.1 If the placenta doesn’t anchor correctly to the uterine wall, and fetal molecules seep into the mother’s bloodstream, it can lead to conditions like preeclampsia.

Debunking a Myth: Immune Suppression During Pregnancy

Contrary to long-held beliefs, pregnancy doesn’t weaken the mother’s immune system. Instead, it fine-tunes the immune response to selectively accept the fetus.2,3 The intricate ways that the immune response is altered to selectively accept the growth of an “alien in the belly” remains a subject of fascination for researchers, especially those exploring ways to prevent graft rejection post-transplantation.

Dive Deeper into Pregnancy Science

As we use tools like Pregspect’s due date calculator to plan and forecast the pregnancy journey, delving into the science behind it enriches our understanding and admiration for the process. Want to learn more? Explore related articles and tools on our website and embrace the wonders of pregnancy science.



Understanding the Complexity of the Immune System during Pregnancy. American Journal of Reproductive Immunology. 2014. Volumen 72 (107-116). Karen Racicot, Ja-Young Kwon, Paulomi Aldo, Michelle Silasi, Gil Mor


Maternal immunological adaptation during normal pregnancy. Frontiers in immunology. 2020. Volume 11. Bahaa Abu-Raya, Christina Michalski, Manish Sadarangani, Pascal M. Lavonie


Adaptive immune response during pregnancy. American Journal of Reproductive Immunology. 2013. Volumen 69 (291-303). Ana Claudia Zenclussen


The photography was taken by André Adjahoe and downloaded from Unsplash.