Maternal Anti‐Placental Cell‐Mediated Reactivity and Spontaneous Abortions

PROBLEM: Does Th1/Th2 balance determine pregnancy outcome, and if so, what determines Th1/Th2 balance in pregnancy? METHOD: Review and synthesis of existing data. RESULTS: A bias toward Th1 is strongly correlated with pregnancy failure in mice and humans. Pregnancy usually shifts the balance toward Th2 and placental factors/progesterone and progesterone-stimulated CD8+ T cell production of suppressor factor; TGFbeta2 and IL4/10 may be responsible. The bias toward a Th1 response may result from intracellular parasitic infection and other as yet undefined factors. CONCLUSION: The Th1/Th2 balance thesis appears to be valid.