Rapid exclusion of chromosomal aneuploidies by fluorescence in situ hybridization prior to fetal surgery for obstructive uropathy--a case report

Prenatal diagnosis from fetal urine in bladder outlet obstruction: success rates for traditional cytogenetic evaluation and interphase fluorescence in situ hybridization

PURPOSE

To determine the optimal approach to the prenatal chromosome analysis of fetal urine from fetuses with bladder outlet obstruction.

METHODS

Retrospective evaluation of traditional cytogenetic and interphase fluorescence in situ hybridization (FISH) analysis on fetal urine specimens from fetuses with bladder outlet obstruction.

RESULTS

Traditional cytogenetic analysis was successful on 71 (95%) of 75 samples, and FISH was informative on 20 (65%) of 31 specimens. The combination of traditional cytogenetic analysis and FISH yielded a 96% diagnostic success rate. The mean turnaround time was 8 days (range 5-14) for traditional cytogenetic analysis and 1.6 days (range 1.0-4.0) for FISH. Chromosome abnormalities were detected in 6 (7.9%) of 76 pregnancies.

CONCLUSION

Traditional cytogenetic analysis achieves a high success rate (95%) and is superior to FISH for chromosome evaluation of fetal urine. However, FISH, when informative, can complement traditional cytogenetics as it will expeditiously rule out common trisomies in fetuses with bladder outlet obstruction.

The role of fetal karyotyping from unconventional sources

OBJECTIVE

Our purpose was to determine whether fetal specimens, including pleural, ascitic, pericardial, facial, and cystic hygroma fluid or urine, are suitable sources for accurate chromosomal analysis.

STUDY DESIGN

Thirty-nine samples of fetal fluid (pleural, n = 11; ascitic, n = 5; pericardial, n = 1; lung cyst, n = 1, facial cyst, n = 1; cystic hygroma, n = 7; and urine, n = 13) were cultured and analyzed with standard cytogenetic techniques for lymphocytes or amniotic fluid. These samples were obtained as part of the routine obstetric investigation and management. Conventional backup samples were also obtained.

RESULTS

Karyotyping was successful in 34 of 39 samples. Cells were harvested from all pleural samples, three ascitic samples, and one hygroma fluid sample in 2 to 4 days from 11 urine samples, one ascitic sample, and the remaining six hygroma samples in 7 to 11 days. Five cultures were unsuccessful. Samples with high lymphocyte counts yielded results as quickly as fetal blood.

CONCLUSION

The use of "alternative" samples of fetal fluids for karyotyping may be considered when amniotic fluid or fetal blood is difficult to obtain. In selected cases this approach avoids the unnecessary risk of additional invasive procedures solely to obtain a karyotype.