Fast multicolor primed in situ protocol for chromosome identification in isolated cells may be used for human oocytes and polar bodies

OBJECTIVE: To present and evaluate the use of a new ultra-fast multicolor primed in situ (PRINS) procedure for karyotyping human oocytes and first polar bodies. DESIGN: In situ chromosomal identification on isolated cells, using combinations of specific primers for chromosomes 1, 7, 9, 16, and 18 and fluorescent nucleotides. SETTING: Sixteen unfertilized oocytes were obtained from women participating in an IVF program. PATIENT(S): Five patients undergoing an IVF-ET. INTERVENTION(S): In vitro unfertilized oocytes were fixed on slides, and sequential PRINS reactions were performed on each preparation. MAIN OUTCOME MEASURE(S): Ultrarapid in situ identification of three or four chromosomes on oocyte and polar body chromosome spreads. RESULT(S): On the basis of the direct in situ mixing of the colors of fluorochromes (FITC, TRITC, Cascade Blue) that were incorporated in sequential PRINS reactions, this method allows rapid and efficient labeling of three or four individual chromosomes. Each PRINS reaction consists of a unique 4- to 6-minute step for both in situ annealing and elongation. The procedure can be combined with fluorescence in situ hybridization (FISH) reactions. CONCLUSION(S): By simplifying the multicolor PRINS procedure, this new protocol should facilitate the use and adaptation of PRINS to chromosome screening. This approach could be used in parallel or in combination with FISH for efficient aneuploidy assessment on isolated cells.     

Validation of primed in situ labeling for interphase analysis of chromosomes 18, X,and Y in uncultured amniocytes

OBJECTIVE: Primed in situ labeling (PRINS) is an interesting alternative to the traditional fluorescence in situ hybridization (FISH) for the in situ detection of specific sequences in chromosome anomalies. It combines the sensitivity and specificity of the polymerase chain reaction with the specific in situ signal detection capability of FISH. METHODS: We performed PRINS on uncultured amniocytes and compared the results with standard cytogenetic analysis. In a prospective study, a total of 262 independent samples were analyzed for numerical aberrations of chromosome 18. RESULTS: In more than 95% of the cases PRINS reactions were successfully achieved. Neither false-positive nor false-negative results were obtained. 62 of the 262 cases were in parallel examined for chromosome 18 aneuploidies by FISH. Although there were significant differences in signal distribution, these did not lead to a different overall classification of the respective cases, i.e., the end results of disomic and trisomic cases for chromosome 18 were identical between FISH and PRINS. In 205 of 262 cases PRINS was performed for chromosomes X and Y. 97.6% of these samples were properly sex differentiated. CONCLUSIONS: The PRINS assay is a simple and cheap alternative to detect numerical aberrations of chromosome 18. However, the rate of false-positive results for chromosome X was calculated as 1% and the rate of false-negative ones for chromosome Y as 2%. Further investigations are required to transform PRINS into an alternative to conventional methods for routine rapid prenatal diagnosis of gonosomes.     

Preimplantation Diagnosis of Common Aneuploidies by the First- and Second-Polar Body FISH Analysis

Purpose: A low pregnancy rate in in vitro fertilization (IVF) patients of advanced maternal age may be caused by aneuploidies originating from non disjunction in the first or second meiotic divisions. We introduced genetic testing of oocytes by sampling and fluorescent in situ hybridization (FISH) analysis of the first and second polar bodies, to avoid fertilization and transfer of aneuploid oocytes in IVF patients of advanced maternal age. Methods: Three hundred and sixty-three IVF patients 34 years and older participated in the study. Using micromanipulation procedures, the first and second polar bodies were removed following their extrusion from the oocytes and studied by FISH, using probes specific for chromosomes 13, 18, and 21 to detect oocytes with common aneuploidies. Results: Of a total of 538 IVF cycles, 3250 oocytes were available for FISH analysis, with conclusive FISH results in 2742 oocytes (84.3%). As many as 1102 (40%) of oocytes were predicted to be aneuploid and not transferred. Of 1640 embryos predicted to be normal, 1145 were transferred in 467 treatment cycles, resulting in 107 pregnancies (23%), from which 67 healthy children have been born, 32 pregnancies spontaneously aborted, and 15pregnancies are ongoing after being confirmed normal by prenatal diagnosis. Conclusions: Preimplantation diagnosis by first- and second-polar body FISH analysis allows us to avoid the age-related risk of common aneuploidies in IVF patients of advanced maternal age.     

Polar body diagnosis of common aneuploidies by FISH

Purpose: The purpose of this work was to investigate the reliability and accuracy of polar body analysis for preimplantation diagnosis of common aneuploidies in IVF patients of advanced maternal age. Design: We have previously introduced polar body analysis as an approach for nondestractive evaluation of the genotype of human oocytes. The method has recently been applied in a clinical trial involving 45 infertile patients, demonstrating the feasibility of preconception diagnosis of common aneuploidies by fluorescent in situ hybridization (FISH). The present paper describes the experience of polar body diagnosis in 135 IVF patients (161 cycles) of advanced maternal age. Results: FISH results of the first and/or second polar bodies were available in 648 (72.4%) of 895 biopsied oocytes subjected to FISH analysis. Of 648 oocytes with FISH results, 208 demonstrated chromosomal abnormalities. Of 440 oocytes predicted to be free from monosomy or trisomy of chromosomes X, 18, and/or 13/21, 314 were normally fertilized, cleaved, and transferred in 122 treatment cycles, resulting in 6 healthy deliveries and 12 ongoing pregnancies following confirmation of the polar body diagnosis by CVS or amniocentesis. Conclusion: The method may be useful for detection of oocytes with common chromosomal trisomies in IVF patients of advanced maternal age.Presented at the 5th Annual Meeting of the International Working Group on Preimplantation Genetics, Hamburg, Germany, June 28, 1995.     

Outcome of laser-assisted polar body biopsy and aneuploidy testing

Polar body biopsy and subsequent fluorescence in-situ hybridization (FISH) analysis allows detection of maternally derived chromosomal aneuploidies in human oocytes during IVF treatment. The development of a diode laser technique for the partial opening of the zona pellucida has stimulated the use of this technique to assist polar body biopsy. Laser-assisted polar body biopsy was performed in 140 IVF cycles from patients of advanced maternal age (> or =35 years). A total of 921 oocytes were treated by a laser for partial zona opening and polar body removal. FISH was performed for chromosomes 13, 16, 18, 21 and 22 and results were available for 903 oocytes (98%). In all, 443 oocytes (49.1%) were euploid and of these, 293 were fertilized. A total of 214 embryos were transferred in 120 embryo transfer cycles (1.78 per embryo transfer) resulting in 27 clinical pregnancies (22.5% per embryo transfer) with an implantation rate of 15.4%. Subsequently, five women aborted (18.5%) and 24 healthy children were born from the remaining 22 pregnancies, which gives a take home baby rate of 18.3% per transfer cycle. It is concluded that polar body biopsy using a diode laser system is as efficient as standard polar body biopsy using zona drilling.     

Preimplantation genetic diagnosis for aneuploidy screening in early human embryos: a review

Embryonic aneuploidies may be responsible for pregnancy failure in many IVF patients. In recent years, fluorescent in situ hybridisation (FISH) for multiple chromosomes has been used to document a high frequency of chromosomal errors and aneuploidy in human preimplantation embryos and, after embryo biopsy, to select embryos that are more likely to implant. Such studies suggest that women with recurrent miscarriage and advanced maternal age may benefit most from preimplantation genetic diagnosis with aneuploidy screening (PGD-AS). The success of PGD-AS is likely to be enhanced by new technologies, such as comparative genomic hybridisation, which enable full karyotyping of single cells.     

采用第一极体进行植入前诊断的实验研究

目的 :建立采用第一极体植入前染色体非整倍体诊断的方法。方法 :取试管婴儿后的未受精卵细胞 ,激光打孔法行第一极体活检 ,固定后行多色荧光原位杂交 (FISH) ,分析极体中 13,16 ,18,2 1和 2 2号染色体的核型情况。结果 :活检成功率为 94 .7% ,FISH成功率为 86 .7% ,6 1.5 %的极体核型正常 ,38.5 %的极体为非整倍体。结论 :激光打孔结合FISH法是一种快速有效的极体植入前诊断方法     

Efficient combined FISH and PRINS technique for detection of DAZ microdeletion in human sperm

Intracytoplasmic sperm injection (ICSI) now offers an effective therapeutic option for men with male infertility and is believed to allow transmission of genetically determined infertility to the male offspring. Transmission of DAZ (Deleted in Azoospermia) microdeletion is one of the major concerns for oligo and severe oligozoospermia patients. Screening of the Y chromosome microdeletion in the diagnostic work-up of infertile men is mainly done using polymerase chain reaction (PCR) on blood leukocytes. However, there are evidences showing that presence of DAZ in somatic cells might not be indicative of its presence in germ cell lineage. In this report we are going to describe a combined Primed in situ labeling (PRINS) and fluorescence in situ hybridization (FISH) technique to show the localization of DAZ gene as well as Y chromosome centromere on sperm nuclei. PRINS is a combination of FISH and in situ polymerization provides another approach for in situ chromosomal detection. In the present study the PRINS primers specific for DAZ genes and traditional direct labeled centromere FISH probes for Y and X chromosomes were used in order to simultaneously detect DAZ genes and sex chromosome aneuploidy in sperm samples.     

Morphological and cytogenetic analysis of intact oocytes and blocked zygotes

We examined cytological and cytogenetic parameters of 1076 oocytes and 385 zygotes that failed to develop post in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Out of 1076 oocytes, 894 (83%) arrested oocytes showed a first polar body and were thus assumed arrested at metaphase II while the remainder showed no polar body. In the group of oocytes with a polar body, 20.5% had an abnormal karyotype. Cytologically, premature sperm chromosome condensation was noted in 28.3% of uncleaved oocytes. This high PCC can be explained by the different grades of oocyte maturity from one center to another. Oocytes from older women showed no increased aneuploidy but did show increased premature chromosome condensation.Analysis by classical technique of 220 uncleaved zygotes showed 91 with highly condensed chromosomes, 53 with asynchrony of condensation, 31 with pulverized chromosomes, and 45 arrested at the first somatic metaphase. Out of 385 arrested zygotes, 165 were explored by in situ hybridization. FISH using a set of 7 chromosome-specific probes showed aneuploidy in the chromosomes analyzed (13, 16, 18, 21, 22, X, Y) in 21.8% of blocked zygotes (19-25% depending on morphology). Extrapolating to other chromosomes, we expect that a vast majority of blocked zygotes and oocytes probably carry chromosome abnormalities. These data demonstrate the contributions of chromosome disorder in early embryo development blocking and implantation failure. Certainly, the issue of cytoplasm and nuclear immaturity and their relation to each other and to chromosome abnormalities provides a fertile area for future investigation in ART.     

Assessing the Chromosome Copy Number in Metaphase II Oocytes by Sequential Fluorescence in Situ Hybridization

Purpose: Aneuploidy in oocytes is the main cause of failed embryo implantation and of miscarriage. At present, only limited data on the prevalence of aneuploidy in freshly collected human oocytes are available and all studies have been performed with conventional methods for karyotyping. In this feasibility study, multiple-hybridization fluorescence in situ hybridization (FISH) was evaluated as an alternative method to determine the number of chromosomes in oocytes. Methods: Fifty-two spare oocytes were collected from 23 patients treated with gonadotropins for intrauterine insemination or intracytoplasmic sperm injection. A conventional dual color FISH approach using mixtures of chromosome-specific standard alpha-satellite probes was applied consecutively to the chromosomes of the same metaphase II oocyte. Mixtures of three to six probes were designed in order to allow chromosome identification based on signal color and centromeric index. Results: One hybridization cycle was possible in 52 uninseminated metaphase II oocytes, two hybridizations in 43 oocytes (82.7%), three hybridizations in 30 oocytes (57.6%), four hybridizations in 27 oocytes (51.9%), and five hybridizations in 15 oocytes (28.8%). Altogether, 591 chromosomes could be marked (47.4% of the entire chromosome complement, 11.4 chromosomes per oocyte). The most important single factor contributing to technical failure was loss of the oocyte from the slide. Conclusions: This feasibility study demonstrates that multiple-hybridization FISH can be used for the assessment of a larger proportion of the chromosome complement in oocyte as compared to previous studies based on FISH.     

Rapid chromosome detection in human gametes,zygotes, and preimplantation embryos using the PRINS technique

Purpose: The analysis of the chromosomal constitution of human gametes and embryos is of particular importance for investigation of aneuploidy occurrence and diagnostic purposes. The PRINS method constitutes an alternative to FISH for in situ chromosomal identification. We have adapted this method to human gametes, zygotes, and preimplantation embryos. Results: Chromosome-specific labeling was obtained in gametes, zygotes, and isolated blastomeres. Simultaneous detection of two or three chromosomes can be completed in less than 3 hr using fluorochrome-labeled nucleotides. Conclusions: The PRINS technique appears to be more efficient than FISH for detection and discrimination of -satellite DNA sequences. The present study demonstrates the usefulness of PRINS for chromosomal screening and preimplantation diagnosis.     

FISH analysis of 15 chromosomes in human day 4 and 5 preimplantation embryos: the added value of extended aneuploidy detection

OBJECTIVE: Screening for an increased number of chromosomes may improve the detection of abnormal embryos and thus contribute to the capability of preimplantation genetic screening (PGS) to detect the embryo(s) for transfer in IVF with the best chance for a healthy child. Good-quality day 4 and 5 embryos were analyzed after cryopreservation for the nine chromosomes mostly recommended for screening (13, 14, 15, 16, 18, 21, 22, X and Y), next to six additional chromosomes which are less well studied in this context (1, 2, 7, 6, 10 and 17). METHOD: The copy numbers of 15 chromosomes were investigated by fluorescence in situ hybridization (FISH) in three consecutive rounds. The proportion of aneuploid and mosaic embryos was determined and compared in retrospect to results in case only the recommended probe set had been analyzed. RESULTS: A total of 52 embryos from 29 infertile women were analyzed. Screening the embryos for six additional chromosomes increased the proportion of abnormal embryos from 67 to 81% (P = 0.03), owing to an increase in mosaic embryos. CONCLUSION: All but one of the meiotic aneuploidies found in this study would have been detected by the probe set most frequently used in PGS clinics. However, aneuploid cell lines originating from mitotic errors could be detected for almost all chromosomes, so screening of six additional chromosomes mainly increased the proportion of mosaic embryos. The added value of screening for six additional chromosomes in PGS for clinical practice will remain undetermined as long as the fate of mosaic embryos after transfer is unclear.     

荧光原位杂交与核型分析技术产前诊断非整倍体的对比研究

目的:在羊水未培养细胞样本中建立并优化荧光原位杂交技术,应用国产探针检测,探讨其诊断未培养羊水细胞非整倍体的临床应用价值。方法:对100例孕12~27周未培养羊水细胞进行FISH快速产前诊断,对5条染色体(X、Y、13、21和18号)进行检测。以细胞培养常规核型分析作为FISH检测结果的对照。结果:被检100例羊水未培养细胞均获得诊断结果,检测出7例非整倍体,FISH结果与核型分析结果一致。结论:应用国产探针行FISH诊断未培养羊水细胞非整倍体,实验方法成熟稳定,结果准确可靠,符合产前诊断要求,有较大的临床应用价值。     

Correlation between oocyte morphology and the embryo aneuploidy rate in IVF cycles

Abstract

Purpose: To evaluate the aneuploidy rates of 13, 18, and 21 and the X and Y chromosomes in embryos from patients with morphologically normal oocytes and different oocyte dysmorphisms.

Methods: This prospective cohort study included 84 patients treated with in vitro fertilization (IVF) at a single academic center. The patients were divided into the following three groups: group 1 – women with cytoplasmic dysmorphisms (n?=?28), group 2 – women with extracytoplasmic dysmorphisms (n?=?28), and group 3 – women with morphologically normal oocytes (n?=?28). One blastomere from each embryo was analyzed for aneuploidies of chromosomes 13, 18, 21, X, and Y.

Results: The highest prevalence of aneuploid embryos was observed in the group 1 (68.4%) followed by the group 2 (38.9%) and the group 3 (31.3%) (р?<?0.0001). The adjusted OR for receiving an aneuploid embryo in the case of cytoplasmic dysmorphism was 3.6 (95% CI?=?1.8; 7.2), in the case of extracytoplasmic dysmorphisms – 1.3 (95% CI?=?0.7; 2.1).

Conclusions: Women with morphological oocyte abnormalities are at risk for developing aneuploid embryos during IVF cycles. We recommend that woman with cytoplasmic oocyte dysmorphisms receive additional genetic counseling to define the indications for the genetic screening of embryos.     

Detection of aneuploidy in human oocytes and corresponding first polar bodies by fluorescent in situ hybridization

Purpose: The purpose of the study was to investigate the reliability of the fluorescent in situ hybridization (FISH) analysis of the first polar body (IPB) for cytogenetic evaluation of human oocytes as a method of choice in preimplantation diagnosis of chromosomal aneuploidies. Design: Human unfertilized oocytes and their extruded IPB were analyzed using the directly labeled fluorescence alpha-satellite DNA probes to chromosomes X and 18. Results: Paired signals for chromosomes X and 18 were observed in the second meiotic prophase (MII) of unfertilized oocytes and their extruded IPB. In the series of 156 unfertilized oocytes in which the number of X chromosome-and chromosome 18-specific signals were analyzed in both MII and IPB, five nondisjunction events have been detected, with corresponding signals in MII and their IPB: missing signals in MII corresponded to extra signals in their IPB and extra signals in MII corresponded to missing signals in IPB. In one oocyte chromosome 18 nondisjunction was detected, with both chromosome 18 signals in MII and no chromosome 18 signal in IPB. In four oocytes chromatid malsegregations for chromosome X or chromosome 18 were detected: in two oocytes, three of four chromosome 18 signals were present in MII, with only one in IPB, and in the other two oocytes, three of four chromosome signals were present in MII, with only one left in IPB. Conclusions: The data suggest the possibility of detecting chromosomal aneuploidy in oocytes through cytogenetic analysis of their corresponding IPB by FISH as a possible approach for preimplantation diagnosis of major chromosomal trisomies.Presented in part at the IXth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction, Vienna, Austria, April 3–7, 1995.     

Fluorescence in situ hybridization analysis of human oocytes: advantages of a double-labeling procedure

OBJECTIVE: To improve the fluorescence in situ hybridization (FISH) chromosomal analysis of human oocytes and first polar bodies. DESIGN: In situ chromosomal identification on isolated cells, with combinations of centromeric (or locus-specific) probes and whole-chromosome painting probes for chromosomes 9, 13, 16, 18, 21, and X. SETTING: Montpellier University Hospital. PATIENT(S): Women participating in an IVF program. INTERVENTION(S): Fifty-four in vitro unfertilized oocytes were fixed on slides, and simple or double FISH labeling procedures were performed on preparations. MAIN OUTCOME MEASURE(S): Simultaneous in situ visualization of specific domains and chromosome arms of each targeted chromosome. RESULT(S): Eight chromosomal abnormalities were identified, including two hyperhaploidies, three cases of extra single chromatid, and three cases of balanced separation of sister chromatids. Also, the double-labeling procedure allowed the avoidance of five interpretation errors, owing to additional artefactual signals. CONCLUSION(S): By ensuring precise identification of both chromosomes and single chromatids, the FISH double-labeling procedure limits the risk of erroneous interpretation and allows a more accurate cytogenetic analysis of human oocytes.     

Chromosome 21 Detection in Human Oocyte Fluorescence In Situ Hybridization: Possible Effect of Maternal Age

Purpose: The purpose of this study was to evaluate, among 100 uncleaved oocytes, the incidence of numerical and structural chromosome 21 and X abnormalities and to analyze the influence of various factors, such as in vitro (IVF) indications, follicle stimulation protocols, and women's age. Methods: We investigated 150 uncleaved oocytes from 128 patients after an IVF attempt. After cytogenetic analysis (Giemsa) 100 oocytes (66%) were selected for fluorescence in situ hybridization (FISH). Fluorescent probes for human chromosomes X and 21 were used simultaneously according to standard procedures for their hybridization and detection. Results and Conclusions: We analyzed by the FISH protocol 100 metaphase II oocytes with 22 to 25 chromosomes. Our results demonstrate a high rate of disomy for chromosome 21 in human oocytes. Among them, eight were disomic (8%) and three were nullosomic (3%) for chromosome 21. Only one disomy of chromosome X was noted. The various indications of IVF and the different folliculogenesis stimulating protocols did not seem to influence the results but suggested a correlation between the maternal age and the aneuploidy rate of chromosome 21.     

Chromosomal abnormalities in a series of 6,733 human oocytes in preimplantation diagnosis for age-related aneuploidies

Most chromosomal abnormalities originate from female meiosis and contribute significantly to pregnancy failures, particularly in women of advanced maternal age. A total of 8,382 oocytes were obtained in 1,297 IVF cycles from patients of advanced maternal age (mean 38.5 years). Following a standard IVF protocol, oocytes were tested following removal and fluorescence in-situ hybridization (FISH) analysis of the first (PB1) and second polar bodies (PB2), using probes specific for chromosomes 13, 16, 18, 21 and 22 (Vysis). FISH results were available in 67,33 (80.3%) oocytes tested, 3,509 (52.1%) of which were aneuploid, with the remaining 3,224 (47.9%) normal oocytes available for transfer. In all, 41.7% of oocytes had meiosis I errors, compared to 35.1% with meiosis II errors. Abnormalities in meiosis I were represented by extra chromatids in 15.4%, missing chromatids in 48.1%, missing chromosomes in 5.9%, extra chromosomes in 0.5%, and complex abnormalities in 30.1%. The proportions of abnormal oocytes with missing or extra chromatids in meiosis II were 36.6 and 41.2% respectively, with the remaining oocytes having complex abnormalities, involving missing or extra chromatids of different chromosomes (22.1%) following meiosis II. Overall, 41.8% oocytes had meiosis I, 30.7% meiosis II, and 27.6% both meiotic division errors. A total of 45.1% of the abnormal oocytes had complex errors, involving the same chromosome in both meiotic divisions (21.5%), or different chromosomes (78.5%), of which 74.8% were with abnormalities of two, and 25.2% with abnormalities of three chromosomes studied. Of 3,224 detected aneuploidy-free zygotes, 2,587 were transferred in 1,100 treatment cycles (2.35 embryos per transfer), resulting in 241 (21.9%) clinical pregnancies and 176 healthy children born, suggesting a positive clinical outcome following aneuploidy testing of oocytes in a group of IVF patients of average age 38.5 years.     

Advanced FISH with directly labeled X, Y and 18 DNA probes as a tool for rapid prenatal diagnosis.

OBJECTIVE: To examine a rapid technique for identification and determination of fetal sex chromosomes and one autosome (chromosome 18) in uncultured amniotic fluids using fluorescence in situ hybridization (FISH) with directly labeled DNA probes and ignoring the use of proteinase K and Rnase. STUDY DESIGN: Twenty-five amniotic samples taken from pregnant women who were in their 18th gestational week and had advanced maternal age were studied for analysis of sex chromosomes and chromosome 18 with the FISH technique as well as standard cytogenetic analysis. RESULTS: Four hours after amniocentesis was performed, we identified the sex of the fetuses and disomy of chromosome 18 in a minimal sample of uncultured amniotic fluid by using directly labeled DNA probes for chromosomes X, Y and 18 (VYSIS) and ignoring the use of proteinase K and Rnase. CONCLUSION: The possibility of shortening the time required for identification of aneuploidies in a second-trimester fetus is useful in cases where fetal anomalies are ultrasonically diagnosed at a relatively advanced gestational age.     

Effectiveness of prenatal chromosomal analysis using multicolor fluorescent in situ hybridisation

Objective To evaluate the clinical effectiveness of multicolour fluorescent in situ hybridisation (FISH) analysis in routine prenatal diagnosis.
Design Prospective study.
Sample 3203 amniotic fluid samples.
Methods Unique DNA (chromosomes 13 and 21) and α satellite centromeric-specific (chromosomes X, Y and 18) probes were used in two mixes to permit the simultaneous analysis of several chromosomes. The performance of multicolour FISH and conventional cytogenetic analysis was compared.
Results Conventional cytogenetic analysis identified 111 chromosomal abnormalities, of which 94 were potentially detectable by the FISH technique and 97 would be typically associated with neonatal phenotypic abnormalities. Multicolour FISH analysis detected 84% (93/111) of all chromosome abnormalities and 99% (93/94) of abnormalities where there was a specific probe. The sensitivity of multicolour FISH analysis was 95% (92/97) for chromosomal abnormalities likely to result in an abnormal postnatal outcome. Multiple ultrasound abnormalities were detected in all five cases of clinically relevant chromosomal abnormalities missed by multicolour FISH. FISH results were available within 48 hours and the sample failure rate was 0.1% (3/3202).
Conclusion Multicolour FISH analysis is a sensitive and reliable technique for the rapid prenatal diagnosis of chromosomal abnormalities. Examining only five chromosomes allowed 95% of clinically relevant chromosomal abnormalities to be diagnosed correctly. As routine antenatal screening is targeted at the major autosomal trisomies and sex chromosome aneuploidies, multicolour FISH analysis may potentially replace conventional cytogenetic analysis in routine prenatal diagnosis.