What procedure is recommended to evaluate platelet count in a fetus with suspected NAIT?

In cases of suspected Neonatal Alloimmune Thrombocytopenia (NAIT), the most appropriate procedure for evaluating platelet count in the fetus is percutaneous umbilical blood sampling (PUBS). This invasive procedure allows for direct access to fetal blood, enabling a precise measurement of the platelet count.

PUBS involves the insertion of a needle through the abdominal wall into the umbilical vein, which provides a sample of fetal blood. This is crucial as it not only assesses the platelet level but can also help determine the presence of fetal anemia or other blood abnormalities. The accuracy of the platelet count obtained through PUBS makes it the preferred method in such cases.

Other options, such as amniocentesis and chorionic villus sampling, do not provide fetal blood samples directly and are primarily used for genetic testing or assessing amniotic fluid, which can indirectly indicate certain conditions but does not specifically evaluate the platelet count. Transvaginal ultrasound is a non-invasive imaging technique that provides information about the fetus but cannot assess blood parameters like platelet count.