Counseling before fetal blood sampling via cordocentesis is more difficult than that done before amniocentesis because 1) a fetal anomaly has been detected or is very likely, 2) the cordocentesis procedure may have a higher risk than does amniocentesis, and 3) the gestational age is frequently advanced before referral. These factors result in counseling and decision dilemmas that include that 1) the advanced gestational age may preclude the option of termination, 2) fetal prognosis may be poor despite normal cytogenetic results, and 3) the benefit of a diagnosis to provide indications for various delivery options must be weighed against the psychological burden of documenting a chromosome abnormality far in advance of delivery. Thus, counseling before cordocentesis requires engaging the couple in decision making regarding potential management of the pregnancy as a prerequisite to choosing or declining the procedure.

The prenatal diagnosis of sickle cell anemia (hemoglobin SS) can be established by DNA analysis using two highly sensitive techniques (Southern blot and polymerase chain reaction [PCR]). Hemoglobin electrophoresis provides a third, simpler and more rapid, technique to analyze blood from a fetus at risk for sickle cell anemia. The authors present examples of prenatal diagnostic studies using both DNA analysis techniques and hemoglobin electrophoresis. Hemoglobin electrophoresis of fetal hemolysate can provide a simple and rapid alternative method to PCR analysis for the prenatal exclusion of sickle cell anemia, and it is especially useful in cases in which rapid results are needed because of advanced gestational age.

The incidence of monozygotic twins with trisomy 18 is 1 in 1,000,000 births. We report a case diagnosed prenatally with lymphocyte culture from fetal blood samples obtained by cordocentesis. Fetal growth lag and structural malformations detected by ultrasonography indicated chromosomal abnormality. A saline solution infusion technique ensured that cordocentesis obtained a sample from each twin.

Early simultaneous percutaneous umbilical blood sampling (PUBS) and amniocentesis for prenatal diagnosis were undertaken for the first time in a 17-week gestation fetus at risk for the fragile X [fra (X)] syndrome. Metaphase spreads from 300 fetal lymphocytes were examined within 5 days following PUBS, while approximately 5 weeks were required for the analysis of 148 amniocytes. The chromosomes were interpreted as normal (46,XX) and the fetus as fragile X-negative at the time of prenatal diagnosis. This was cytogenetically confirmed after delivery of a healthy term female infant. Our results suggest that early PUBS may become a useful adjunct to amniocentesis because of shorter culture time and earlier diagnosis.