Table 2.

Key changes in maternal adaptive immune system during pregnancy.

Main changes	References
Lower B cell levels in pregnant women compared with non-pregnant women	(26)
B cell lymphopenia in the third-trimester of pregnancy	(25)
Estrogen reduces B cell lymphopoiesis during pregnancy	(27, 28)
Decrease in B cell function	(29)
Decreased total IgG levels, especially during late pregnancy	(30, 31)
High estradiol levels promote T helper 2 cell responses	(32–34)
Elevated progesterone during pregnancy inhibits T helper 1 cell immune responses	(35)
A progressive shift from T helper 1 cell to T helper 2 cell responses	(36)
Decrease in T cell function	(37–39)