Pregnancies affected by fetal and neonatal alloimmune thrombocytopenia (FNAIT) are considered high-risk and can be life-threatening for a fetus or newborn.
FNAIT is a rare disease, and cases of FNAIT in twins and multiple pregnancies are rarer still. According to the few reported cases, the risk of FNAIT in multiple pregnancies can be hard to predict, as each fetus can be affected differently by the maternal HPA-alloantibodies. For example, it is possible for one baby to be severely affected by thrombocytopenia, while the other baby or babies remain unaffected.
As in all cases of FNAIT, early diagnosis and intervention will contribute to positive outcomes.
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare autoimmune blood disorder that affects approximately 0.1% of pregnancies. If the fetus inherits a human platelet antigen (HPA) that the mother doesn’t have, the mother’s immune system identifies it as foreign. This triggers the development of antibodies as an immune response that then cross the placenta and attack the fetus’s blood platelets. This causes the fetus’s blood platelet count to drop to low levels and prevents blood from clotting.
If undiagnosed and untreated, FNAIT can be life-threatening for the fetus and newborn. Bleeding can occur, with hemorrhages in the brain (known as intracranial hemorrhage or ICH), gastrointestinal tract, lungs and eyes holding the greatest risk for the baby.
How FNAIT is diagnosed in twins and multiples
In first pregnancies, regardless of whether there is one fetus or more than one, FNAIT often goes undiagnosed. It is more commonly diagnosed in newborns with bruising and reddish-purple skin discoloration related to thrombocytopenia (low blood platelet count). In twins and multiple pregnancies, unless low platelet levels or bleeding are detected in utero, it is also diagnosed following delivery. In multiple pregnancies, delivery often occurs before term, allowing diagnosis and treatment to take place earlier.
Learn more about FNAIT testing and diagnosis
In subsequent pregnancies, when the risk of FNAIT is known, specialized and close monitoring are standard. In the case of multiple pregnancies, this level of care will be intensified, to address the usual challenges of multiple pregnancies, coupled with the potentially life-threatening complications of FNAIT. Not all babies are sure to have the same outcomes. For example, it is possible for the babies to not all have the inherited HPA type, meaning they will not all be affected by the maternal HPA antibodies.
How FNAIT is treated in twins and multiples
If FNAIT is detected in newborns, urgent first-line treatment involves platelet transfusions, which can rapidly stabilize and increase newborn platelet levels, leading to a good prognosis. However, if ICH has already occurred, long-term neurological damage may already have been caused. In multiple births, each of the babies may present differently.
Whether it is diagnosed during pregnancy or post-delivery, FNAIT in twins and multiple pregnancies presents unique challenges, with a different, personalized treatment plan required for each baby. A multidisciplinary healthcare team, headed up by a maternal-fetal specialist and a hematologist will closely monitor the babies throughout pregnancy, birth and postnatally.
