Prenatal karyotyping using fetal blood obtained by cordocentesis: Rapid and accurate results within 24 hours

Spontaneously-dividing nucleated erythrocytes present in prenatal cordocentesis samples can be used to obtain fetal karyotype information within 24 hours. Following a modified protocol we performed rapid chromosome analysis on fetal blood from 70 second- and third-trimester fetuses. In all cases cordocentesis was performed following detection of ultrasound abnormalities. Cytogenetic diagnoses were obtained within 24 hours from 59 (84.3%) of the 70 samples. Follow-up chromosome analysis from mitogen-stimulated cultures showed concordant results in 57 of the 59 successful cases. In one case a mosaicism for 45,X[4]/46,X,i(X)(q10)[4] was detected in unstimulated harvest while mitogen-stimulated preparations showed only the 46,X,i(X)(q10) line. In the second case, a marker chromosome was identified in all 5 cells analyzed from the unstimulated harvest while mitogen-stimulated cultures showed only 4 out of 100 cells with the marker. Our experience confirms that blood obtained by cordocentesis can be an excellent source for rapid prenatal diagnosis. Furthermore, direct processing of fetal blood may be more sensitive in delineating tissue-limited abnormalities than mitogen-stimulated preparations.