When fetal and neonatal alloimmune thrombocytopenia (FNAIT) is suspected in a newborn, a cranial ultrasound will likely be performed immediately after delivery to check for intracranial hemorrhage (ICH).
FNAIT diagnostic tests are not the priority if it is suspected, as ICH requires much faster treatment, so FNAIT likely won’t be confirmed until later. If ICH is suspected, your care team will work to boost blood platelet levels and understand the severity of FNAIT by checking for bleeding on the brain. Early detection and intervention are essential to successful outcomes.
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition that affects 0.1% of pregnancies in which a pregnant mother’s immune system produces antibodies against the platelets of her fetus. This occurs when a fetus inherits platelet antigens from the father that are not compatible with the mother, typically involving a protein called human platelet antigen (HPA). The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopenia) in the fetus or newborn.
What is a cranial ultrasound?
A cranial ultrasound is a non-invasive and painless imaging tool that takes high-definition real-time images of the brain with the help of sound waves. It is a highly accurate diagnostic tool and is used in diagnosing abnormalities in the body’s organs, tissues and internal structures.
In newborns suspected of FNAIT, the doctor will look for bleeding on or in the brain, which can occur if the blood is not clotting as a result of a low platelet count. It can occur during pregnancy as well as after delivery. If not detected in time, and without urgent platelet transfusions to treat thrombocytopenia, ICH can have long-term neurological consequences and even cause death.
Learn more about FNAIT signs and symptoms
What to expect from a cranial ultrasound
A cranial ultrasound will likely not cause your baby any pain or discomfort. It is over relatively quickly, taking only 15-30 mins. You do not need to do anything before the appointment unless told otherwise by your doctor, and there are no known side effects. The ultrasound machine is portable and will be brought to your baby’s bedside. You will be asked to swaddle and hold your baby to keep them calm and still during the procedure. Their head will ideally be facing upwards.
The ultrasound technician will apply warm gel to the soft spot on the top of your baby’s head, known as the anterior fontanelle. Then, with a hand-held device lightly placed on the fontanelle, the technician will generate pictures of your baby’s brain. High-frequency sound waves bounce off the inside of your baby’s brain and create high-definition images.
Once the technician is sure to have high-quality images, they will wipe off the gel on your baby’s head. The images will be reviewed by a pediatric radiologist, who will be looking for signs of bleeding on the brain. If an ICH is detected, they will measure the size of the bleed and note its location. Urgent platelet transfusions are required to replace the newborn’s platelets destroyed by maternal antibodies, restoring the blood’s clotting properties and stopping the bleeding.
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