How Does Immunity Change During Pregnancy?

1.Does pregnancy change the risk for infection?
Pregnancy is not so much a suppression of the immune system as it is a “fine tuning” that creates a unique immune condition. Pregnancy shifts mom’s immune system so her body can tolerate a baby, which is genetically “half-foreign.” To allow for the coexistence of the fetus, which is only half mom, a pregnant woman’s body reduces cell-mediated immunity. With cell-mediated immunity, the cells themselves eliminate foreign tissue such as viruses and bacteria without using antibodies. This shift reduces mom’s ability to fight off certain infections, particularly in the second and third trimesters.

2.Instead of cell-mediated immunity, how does the woman’s body deal with foreign viruses and bacteria without using antibodies?

Reduced Cell-Mediated (T-Cell) Immunity
Th1 helper cells produce interferons, a group of proteins released primarily by white blood cells in response to viruses, bacteria, or cancer. These cells serve as crucial early defenders of the immune system, but they are known to promote inflammation.

A Shift from Th1 to Th2 Immunity
When a woman is pregnant, there is a shift away from the pro-inflammatory Th1 response towards an anti-inflammatory Th2 to protect the baby. This shift reduces mom’s ability to fight off certain infections, particularly in the second and third trimesters.

3.How does this change a pregnant woman’s reaction to infection?
Infections can be more frequent and more severe. While not all infections are more likely to be contracted during pregnancy, many such as influenza A and B as well as COVID are more likely to be severe in pregnant women.

4.What infections can cause problems in pregnancy?
Pregnant women are particularly susceptible to certain infections, including the following:

•listeria infection
In pregnancy, a woman is roughly 17 times more likely to get sick from listeria infection, an infection which can cause complications.
•influenza A and B
Influenza during pregnancy is more likely to cause pneumonia and severe respiratory illness.
•COVID
Like influenze A and B, COVID is more likely to cause pneumonia and severe respiratory illness.
•urinary tract infections (UTIs)
UTIs are mre common in pregnancy because of hormonal changes and physical pressure from the baby.
•malaria
In pregnancy, woman are three times more likely to develop severe cases of malaria, especially with a first pregnancy.

5.What infections during pregnancy can directly affect the baby?

•toxoplasmosis, often spread via cat feces or undercooked meat,
•cytomegalovirus, (CMV), a common virus which can cause hearing loss and developmental problems for the baby,
•rubella (German measles) can cause severe birth defects if contracted during the first trimester of pregnancy,
•herpes symplex virus (HSV) can cause brain damage and organ failure,
•syphilis can cross the placenta,
•zika virus is known to be able to cause severe fetal abnormalities,
•chickenpox, especially if the mother is not immune,
•Parvovirus B19 can lead to severe anemia in the baby,
•HIV can cross the placenta, but risk can be managed with antiretroviral medications, and
•hepatitis B and C can infect a baby in utero as well as a baby passing though the birth canal.