Immunosuppressive therapy with tacrolimus is a potential drug candidate for the prevention of unexplained or preeclamptic stillbirths with Th1-dominant immune states: a case series of five patients.

Some of obstetrical complications such as unexplained pregnancy loss and preeclampsia (PE) are associated with maternal-fetal immune abnormalities, leading to uteroplacental dysfunction, insufficient fetal immune tolerance, or fetal rejection. Immunosuppressants with calcineurin inhibitors could be useful for the prevention of these complications by modulating the cellular immune balance by directly inhibiting activated T-helper (Th) 1 and natural killer (NK)/NKT cells. We present our experience with the immunosuppressant tacrolimus in five pregnant women who had a previous pregnancy history of unexplained or preeclamptic stillbirth. Th1 and Th2 cell populations and NK cell activities in peripheral blood were measured as clinical parameters during pregnancy. Case 1-3 achieved suppressions of predominant Th1 immunity and live births without pregnancy-related complications. In case 4, increased tacrolimus dose after a miscarriage resulted in her first live birth; however, she developed PE and severe fetal growth restriction with elevated Th1/Th2 cell ratios at 26 weeks of gestation. Case 5 had a previous history of early onset PE and the hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome, and an emergency cesarean section was needed for maternal safety at 20 weeks of gestation. The course of the next pregnancy was stable under tacrolimus treatment; however, the HELLP syndrome recurred after PE at 33 weeks of gestation. Although an imbalance in the Th1/Th2 cell ratio was not observed during pregnancy, NK cell activity was markedly elevated before delivery. In conclusion, tacrolimus is a potential drug candidate for the prevention of unexplained or preeclamptic stillbirth with Th1-dominant immune states.