Fetal blood sampling in prenatal diagnosis of thalassemia at late pregnancy.

Fetal blood sampling is a procedure that involves the drawing of a blood sample from the umbilical vein of the umbilical cord, which can be performed after 18 weeks gestation. Fetal blood sampling is a preferable method for prenatal diagnosis of thalassemia in second trimester or late pregnancy. Additionally, it is suggested to be performed in cases in which mosaicisms are identified by amniocentesis or chorionic villus sampling (CVS), areas where DNA analysis is not available, and when mutations of the parents are not known. Laboratory steps regarding prenatal diagnosis by fetal blood sampling were summarized, including the ensuring of fetal origin, determination of red blood cell parameters, fetal hemoglobin analysis, and finally fetal DNA analysis. The objective of this review is to present an overview of procedures in terms of benefits, laboratory interpretations, and some limitations.