Pregnancy comprises a unique immunological condition, to allow fetal development and to protect the host from pathogenic infections. Viral infections during pregnancy can disrupt immunological tolerance and may generate deleterious effects on the fetus. Despite these possible links between pregnancy and infection-induced morbidity, it is unclear how pregnancy interferes with maternal response to some viral pathogens.
The potential risk of vertical transmission is unclear, babies born from COVIDpositive mothers seems to have no serious clinical symptoms, the possible mechanisms are discussed, which highlights that checking the children's outcome and more research is warranted. In this review, we investigate the reports concerning viral infections and COVID during pregnancy, to establish a correlation and possible implications of COVID during pregnancy and neonatal's health.
Pregnancy comprises a unique immunological condition, to protect the fetus from maternal rejection, allowing adequate fetal development and protection against microorganisms 1 , 2. The maternal immune system is challenged by paternal alloantigens expressed both by the fetus and the placenta.
However, through a complex range of cells and molecules, the mother does not develop a classic response to this allograft 3. During pregnancy, fetal microquimerism occurs, where fetal cells, such as nucleated erythrocytes, trophoblastic cells, and leukocytes 3 , cross the placental barrier and expose the mother to fetal alloantigens. These cells can remain in the bloodstream and maternal tissues many years after delivery 4 , 5. In comparison to the post-partum period, pregnancy increases monocytes, granulocytes, pDCs, mDCs in the blood, peaking during 2 trimesters.
B cells are decreased during the third trimesters. NK cells CD56 dim are reduced in the second and third trimester of pregnancy in comparison with the first trimester and post-partum period. The absolute number of NK cells in maternal blood increases in the first trimester of pregnancy 9. Like lymphocytes, B cells are decreased during pregnancy and remain lower until 1 month after delivery.
