Quantitative fluorescent polymerase chain reaction for rapid prenatal diagnosis of fetal aneuploidies in chorionic villus sampling in a single institution

Objective

To validate quantitative fluorescent polymerase chain reaction (QF-PCR) via chorionic villus sampling (CVS) for the diagnosis of fetal aneuploidies.

Methods

We retrospectively reviewed the medical records of consecutive pregnant women who had undergone CVS at Cheil General Hospital between December 2009 and June 2014. Only cases with reported QF-PCR before long-term culture (LTC) for conventional cytogenetic analysis were included, and the results of these two methods were compared.

Results

A total of 383 pregnant women underwent QF-PCR and LTC via CVS during the study period and 403 CVS specimens were collected. The indications of CVS were as follows: abnormal first-trimester ultrasonographic findings, including increased fetal nuchal translucency (85.1%), advanced maternal age (6.8%), previous history of fetal anomalies (4.2%), and positive dual test results for trisomy 21 (3.9%). The results of QF-PCR via CVS were as follows: 76 (18.9%) cases were identified as trisomy 21 (36 cases), 18 (33 cases), or 13 (seven cases), and 4 (1.0%) cases were suspected to be mosaicism. All results of common autosomal trisomies by QF-PCR were consistent with those of LTC and there were no false-positive findings. Four cases suspected as mosaicism in QF-PCR were confirmed as non-mosaic trisomies of trisomy 21 (one case) or trisomy 18 (three cases) in LTC.

Conclusion

QF-PCR via CVS has the advantage of rapid prenatal screening at an earlier stage of pregnancy for common chromosomal trisomies and thus can reduce the anxiety of parents. In particular, it can be helpful for pregnant women with increased fetal nuchal translucency or abnormal first-trimester ultrasonographic findings.

Fragile X syndrome prenatal diagnosis: parental attitudes and reproductive responses

Fragile X syndrome (FXS) is the most common inherited form of mental retardation. It is caused by a CGG repeat expansion, which results in hypermethylation and silencing of the FMR1 gene. The results from 213 FXS prenatal diagnoses performed in the study centre were reviewed. Family history of FXS or undiagnosed mental retardation (MR) were the reasons for referral and 64% of mothers were not aware of their status so prenatal and mother tests were performed at the same time. Among those women referred for family history of unknown MR, 17.6% were found to be FXS carriers. The attitudes and perceptions of the syndrome of 52 FXS carriers were also evaluated. Most of them had been diagnosed as carriers when the child was already born and the most common feeling was sadness, followed by impotence and guilt. The majority of them had received genetic counselling and they considered it useful. Regarding reproductive options, prenatal diagnosis was chosen by 40.5% of women. Prenatal diagnosis for FXS is a good reproductive option and it should be carried out whenever family history of MR is present. A high percentage of FXS carriers are detected following this approach.