Quality aspects of prenatal cytogenetic diagnosis: determining the effect of various factors involved in handling amniotic fluid and chorionic villus material for cytogenetic diagnosis

The yield of chromosomal microarray analysis among pregnancies terminated due to fetal malformations

Background: Chromosomal microarray analysis (CMA) is preferred for genetic work-up when fetal malformations are detected prenatally.Objectives: To assess the detection rate of CMA after pregnancy termination due to abnormal ultrasound findings.Methods: CMA was successfully performed in 71 pregnancies using fetal DNA (mainly from skin) or placenta. Data regarding clinical background, pregnancy work-up, and CMA were analyzed.Results: Findings were abnormal in 17 cases (23.9%), of which 13 were detectable by karyotype. The incremental yield of CMA was 4/71 (5.6%); 1/32 (3.1%) for cases with an isolated anomaly and 3/39 (7.7%) for cases with nonisolated anomalies.Conclusions: CMA yield from terminated pregnancies was 23.9%. Although most chromosomal abnormalities are detectable by karyotype, CMA does not require viable dividing cells; hence, it is more practical for work-up after termination. In most cases, the diagnosis was followed by consultation regarding the risk of recurrence and recommendations for testing in subsequent pregnancies.

The yield and complications of amniocentesis performed after 24 weeks of gestation

PURPOSE

This study assessed the use and complications of late amniocentesis (AC) and analyzed factors that affect complication rate.

METHODS

A retrospective analysis of 167 genetic AC performed after 24 weeks during a 10-year period in two medical centers was conducted. Data regarding the indications for AC, genetic work-up, and pregnancy outcomes were retrieved from patient medical records and telephone-based questionnaires.

RESULTS

Mean gestational age (GA) at the time of AC was 31.7 ± 2.7 weeks; 104 procedures were performed at ≤32 weeks, including 24 at ≤30 weeks. The overall pregnancy complication rate occurring at any time after the procedure was 6.6% (11). Of these, 4.8% (8) occurred within a month after AC, including 2.4% (4) that occurred within a week. An additional three occurred after 30 days. There were no differences in the total complication rate and in the rate of specific complications of procedures performed at ≤32 weeks or at ≤30 weeks. Maternal age did not affect outcomes. Genetic testing was abnormal in five cases (3%). Amniocyte culture failed in 3 cases (2.3%), with no technical failures in 52 chromosomal microarray tests.

CONCLUSION

The complication rate of AC performed after 24 weeks was 4.8%, which is significantly higher than that of second trimester AC. GA and maternal age did not affect the complication rate.

An external quality assessment scheme for prenatal detection of rare chromosomal abnormalities

OBJECTIVE

To improve the accuracy of prenatal cytogenetic diagnosis by establishing an external quality assessment (EQA) scheme for rare, or subtle, structural chromosomal abnormalities.

METHOD

Typical metaphase images of rare chromosomal abnormalities along with an anonymized clinical history were sent to 35 prenatal diagnosis laboratories. The laboratories were required to provide independent reports using current nomenclature. Evaluation of reports was based on established criteria for quality assessment of karyotype analysis.

RESULTS

Totally 6 kinds of typical rare chromosomal abnormalities were collected. 35 laboratories were enrolled with a response rate of 94.29%. The overall analytical accuracy is 82.20%. This is comparable with our former EQA scheme using established lymphocyte cell lines with rare abnormal chromosome karyotypes (χ²=0.065, P=0.799).

CONCLUSION

Introduction of efficient EQA for prenatal genetic diagnosis is currently imperative, due to the limited performances of karyotype analysis of rare chromosomal abnormalities. Metaphase images could be used as a simple and effective material for EQA and to improve the quality of prenatal genetic diagnosis.

[The results of cytogenetic analyses in prenatal diagnosis]

INTRODUCTION

G-banding and other classical cytogenetic methods are still in use, together with molecular cytogenetic techniques such as FISH (Fluorescence In Situ Hybridization) and SKY (Spectral Karyotyping).

MATERIAL AND METHODS

This retrospective study evaluated clinical data on individuaols seeking genetic counseling over a 15-year period (1992 - 2007) at the Medical Genetic Center, Child and Youth Health Care Institute of Vojvodina in Novi Sad. The study included 37.191 genetic counselings, and 20.607 prenatal analyses (amniocentesis and cordocentesis).

RESULTS

Over a 15-year period (1992 - 2007) 17.937 amniotic fluid samples were analyzed and 274 abnormal karyotypes were found; out of 2.670 fetal blood samples, there were 78 abnormal karyotypes. During a 15-year period, prenatal diagnosis, using amniocentesis and/or cordocentesis, showed 352 fetuses with chromosomal aberrations.

DISCUSSION

On average, over the past 15-year period, 8% of pregnancies were controlled with invasive prenatal procedures. The percentage has changed; in fact, it is increasing from year to year. In 1992, only 0.82% (N=139/17000) of pregnant women in Vojvodina underwent invasive prenatal procedures, and in 2006 the rate increased to 15.65% (N=2660/17000).

CONCLUSION

It is necessary to improve and promote the possibilities of genetic counseling and invasive prenatal diagnosis in order to prevent the occurrence of chromosomal aberrations and other genetic diseases.

Amniocentesis in the third trimester of pregnancy

BACKGROUND

Amniocentesis in the third trimester, which reduces risks of procedure-related miscarriage but still allows termination of affected fetuses, may be applicable in some pregnancies. The implications of deferring amniocentesis include complications, delivery before the test and increased amniotic fluid culture failure rates. We investigated the indications, complications, karyotype results and laboratory failure rates of third-trimester amniocentesis.

METHODS

We studied all women who underwent third-trimester amniocentesis from 2000 to 2006. Data were collected from ultrasound databases, computerised records and individual chart review.

RESULTS

We reviewed 165 pregnancies that underwent amniocenteses after 28 weeks. Median maternal age at amniocentesis was 32 years and median gestation, 32(+2) weeks. Indications included malformation (60/165), soft markers (37/165), maternal request (12/165), and positive screening test (11/165). Of the 49 women(29.7%) who declined second-trimester amniocentesis, 24.5% had twins and 38.8%, malformations. Amniocentesis was not offered to 116 women: 57/116 (49.1%) third-trimester referrals, 25/116 (21.5%) diagnosed late and the remainder, low-risk indications. Fetal karyotype was abnormal in 17 cases (10.3%). Seven women who initially declined amniocentesis had abnormal results compared with one advised to have late amniocentesis. Culture failure rate was 9.7%, however results were obtained by Quantitative fluorescent polymerase chain reaction (QF-PCR) from 164/165 samples. Complication rate was 1.2%.

CONCLUSION

For late diagnoses and for low-risk indications, third-trimester amniocentesis is an acceptable option, especially when utilising QF-PCR with cytogenetic culture.