Procedure
PUBS is similar to amniocentesis, but instead of sampling the amniotic fluid which surrounds the fetus, PUBS examines fetal blood. An advanced imaging ultrasound determines the location for needle insertion into the placenta, and the needle is guided through the mother's abdomen and uterine wall into the fetal vein of the umbilical cord, where a fetal blood sample is removed. The sample can then be sent for chromosomal analysis. The entire process lasts 45 minutes to an hour. Because the fetal vein is fragile early in pregnancy, PUBS is performed no earlier than 17 weeks into pregnancy.
PUBS testing has a turnaround time of about 72 hours and can detect chromosomal abnormalities, blood disorder, some metabolic disorders, infections, and some causes of structural problems. PUBS has largely replaced fetoscopy, which has a much higher rate of miscarriage.
It has been used with mothers with immune thrombocytopenic purpura.
Read more about this topic: Percutaneous Umbilical Cord Blood Sampling