Microangiopathic Hemolytic Anemia in Pregnancy

Thrombotic microangiopathies (TMAs) are associated with microangiopathic hemolytic anemia and thrombocytopenia, resulting in microvascular thrombosis and end-organ damage. In pregnancy, this may be the result of pregnancy-related TMAs such as preeclampsia; hemolysis, elevated liver enzymes, and low platelets; or pregnancy-associated TMAs, specifically thrombotic thrombocytopenic purpura (TTP) or complement-mediated hemolytic uremic syndrome (CM HUS). TTP and CM HUS are rare disorders, and their diagnosis may be missed, no less because features at presentation may be misdiagnosed as a pregnancy-related TMA, such as hypertension, proteinuria, fetal growth restriction, or in utero fetal death. The mainstay of treatment for pregnancy-associated TMAs is plasma exchange. Presentation is likely in the third trimester for TTP and postpartum for CM HUS. However, both conditions can present in any trimester, unlike pregnancy-related TMAs which rarely present before the second trimester, commonly in the third trimester. Delivery is the mainstay of treatment for pregnancy-related TMAs. More recently, it has become clear that pregnancy may be a trigger for late-onset congenital TTP, as well as immune-mediated TTP, diagnosed by ADAMTS13 analysis. Complement inhibitor therapy is the treatment of choice for CM HUS cases. However, their diagnosis is by exclusion, but complement inhibitor therapy reduces the risk of end-stage renal failure. Subsequent pregnancies can be supported for TTP and CM HUS.