What is the primary purpose of percutaneous umbilical blood sampling (cordocentesis)?

The primary purpose of percutaneous umbilical blood sampling (cordocentesis) is to diagnose and treat abnormal fetal blood conditions. This invasive procedure involves the insertion of a needle through the maternal abdominal wall into the umbilical cord to obtain fetal blood samples. It is particularly valuable for identifying conditions such as fetal anemia, infection, and certain genetic disorders. By analyzing the blood, healthcare providers can assess various fetal health conditions and make timely decisions for interventions or treatments if needed, such as blood transfusions or other therapeutic measures.

While it may be tempting to consider the other options, they do not reflect the primary indication for using cordocentesis. Fetal surgeries, assessing placental function, and determining fetal gender can involve different methodologies and are not the primary focus of this specific procedure. Cordocentesis is primarily aimed at addressing and managing fetal blood conditions, making option B the correct choice.