RESUMO
Pregnancy is not as successful as one might think; it can be compromised by several complications such as recurrent spontaneous miscarriage, pre-term delivery, pre-eclampsia etc. Much attention has been paid to the possibility of the maternal immune system mediating deleterious effects on pregnancy. Research conducted during the last two decades has shed much light on cell-mediated immunologic effectors that might underlie these pregnancy complications. Of particular interest are the effects that pro-inflammatory and anti-inflammatory cytokines have on the foetus and placenta, and thus on the success and failure of pregnancy. This review presents evidences that certain cytokine profiles are associated with recurrent miscarriage and pre-term delivery and discusses possible pathways of effector function of cytokines in pregnancy loss and the redirection of cytokine profiles from one that is antagonistic to pregnancy towards one that is conducive to the success of pregnancy. Among the promising agents for the modulation of the Th1/Th2 balance are progestogens like progesterone and dydrogesterone; this review also discusses recent evidence that progestogens are capable of modulating cytokine production patterns in pregnancy loss.