When fetal and neonatal alloimmune thrombocytopenia (FNAIT) is diagnosed during pregnancy, timely treatment and close fetal monitoring are key to successful outcomes for the baby.
Monitoring options include a Doppler ultrasound to monitor blood flow and detect any abnormalities and a fetal blood sample to check blood platelet levels.
What is FNAIT?
FNAIT is a rare autoimmune hematological disease that can occur in pregnancy as a result of a genetic mismatch of human platelet antigens (HPAs) between the mother and the fetus. The fetus inherits an HPA from its father, which the mother doesn’t have. The mother’s immune system identifies the HPA as foreign and activates an immune response, developing antibodies that cross the placenta and destroy the fetus’s blood platelets.
This can have serious consequences for the fetus, as the function of platelets is to stop bleeding by clotting the blood. If a fetus has a low platelet count (thrombocytopenia), bleeding and hemorrhage can occur. Hemorrhages in the brain and internal organs can cause severe long-term neurological damage, and death.
Learn more about FNAIT treatment and care
How is the fetus monitored during a FNAIT pregnancy?
A fetus affected by FNAIT can be monitored by either invasive or non-invasive procedures. A maternal-fetal specialist and/or a hematologist will perform a risk/benefit assessment to decide how to proceed.
Doppler ultrasound
If a pregnancy is identified as at-risk of FNAIT due to a previously affected pregnancy, or a family history of FNAIT, the fetus will be closely monitored by regular Doppler ultrasounds. If FNAIT is diagnosed, the fetus will continue to be monitored by ultrasounds.
A Doppler ultrasound is a low-risk, non-invasive procedure that shows the blood moving through the baby’s body. It can detect any abnormalities in the internal organs, in particular the heart, head and brain. In FNAIT pregnancies, it will check for any bleeding or hemorrhages.
If an intracranial hemorrhage (ICH) is detected, a magnetic resonance imagination (MRI) will be used to confirm its diagnosis. ICH is a potentially life-threatening complication for the fetus that requires urgent intervention and, in some cases, an emergency cesarean.
Fetal blood sampling
This is an invasive test that uses a very small needle to extract a fetal blood sample, to check blood platelet levels. The sample can be taken from the fetus’s umbilical cord or from a blood vessel (usually from the heart or liver). In FNAIT. it carries the risk of triggering bleeding in the fetus, if the blood platelet count is low. Other risks include infection, leaking of amniotic fluid, changes to the fetus’s heart rate and in rare cases, fetal death.
Monitoring the fetus’s blood platelet levels can guide both prenatal and postnatal treatment of the baby. It can be performed in pregnancies of 18 weeks gestation and later.
