Reproductive Immunology: a delicate balance to a healthy pregnancy

Arguably the least understood aspect of modern reproductive medicine is the complex interaction between a woman’s immune system and a newly arrived embryo into her uterus. The immune cells are the means that your body is protected from anything that is genetically different. Typically, these cells are preventing invasion of viruses, bacteria or parasites. But in order to become pregnant and not experience a miscarriage—the immune system has to not only allow an embryo to “implant” but it has to actually help it establish a health blood supply to grow. Failure to do so, results in a negative pregnancy test, miscarriage or pregnancy complications like preeclampsia, preterm labor or fetal growth restriction.  

Most fertility treatment is focused on helping women initiate a pregnancy. As we’ve gotten better at initiating pregnancy, we need to place greater attention on fostering the changes to help that pregnancy continue to a healthy delivery. That’s the focus of reproductive immunology. Recently I listened to an evidence-based podcast that explains the emerging science that makes this complicated subject very accessible: .**

**This podcast is created by a non-profit so if you found it useful please consider making a donation

One of the most fascinating studies on the maternal-fetal immune response compared the outcomes from women that conceived with their own eggs vs women that used the eggs from an egg donor. Not surprisingly—it was found that women that became pregnant with an egg donor were at greater risk of adverse outcome due to non compatible immune reactions. They also found that using more than one embryo at a time during a Frozen Embryo Transfer was associated with an increased risk—even when women were conceiving with their own eggs. Both of these observations support the hypothesis that a successful pregnancy is dependent upon cooperation between the maternal immune cells and the placenta.

Here are some key points to assist with this reproductive challenge:

  • Transferring ONE embryo instead of two or more reduces the risk of adverse outcome
  • Suppressing the maternal immune reaction with steroids is not helpful and may actually add to risk of pregnancy failure by reducing the ability of maternal cells to support blood flow
  • The need to increase the availability of nutrients to support the growing fetus may explain some of the reason that metformin is associated with a reduction in the risk of miscarriage and of pregnancy complications
  • There are other techniques to optimize the maternal immune response to the placenta. Talk to your provider to determine if any of these treatments would be appropriate for you.

Stay informed,


Robert Greene, MD, FACOG

Conceptions Reproductive Associates of Colorado

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