Feasibility, accuracy and safety of chorionic villus sampling: a report of 10741 cases

Fetal Genetic Diagnosis by Chorionic Villus Sampling: Evaluation of the Five-Year Experience from a Single Center

We summarized our five-year chorionic villus sampling (CVS) experience with indications, detected chromosomal abnormalities and pregnancy outcomes. Materials and Methods: This retrospective study examined 552 patients underwent CVS for prenatal diagnosis between 2014 and 2018. Results: The most frequent patients undergoing CVS indications were abnormal aneuploidy screening results, increased nuchal translucency, and cystic hygroma/edema. Of 552 CVS, 385 were normal, 141 abnormal. Eight were contaminated with maternal cells, 4 were mosaics, in 12 the culture failed, and in 2 there was inadequate sampling. The most frequent chromosomal abnormalities were trisomy 21, trisomy 18 and 45,X. Of 246 followed pregnancies, there were 165 live-births (67,1%), 58 pregnancy terminations (23,6%), and 23 pregnancy losses (9,3%). There were 5 procedure-related losses (2%), 3 of which were chromosomally normal. Conclusion: Although significant advances have been made in noninvasive methods such as NIPT, CVS is still a reliable technique for cytogenetic diagnosis in early gestation.

Ante-natal counseling in phacomatoses

OBJECTIVES

Phacomatoses are a group of neuro-oculo-cutaneous syndromes/ neurocutaneous disorders, involving structures arising from the embryonic ectoderm. Most of phacomatoses including the most common ones:, neurofibromatosis type I and type II (NF1, NF2) and tuberosclerosis complex (TSC), are autosomal dominant genetic disorders with full penetrance and variable expression. As no effective treatment exists, the only way to prevent the disease, is by prenatal genetic diagnosis (either chorionic villus sampling-CVS or amniocentesis-AC) and termination of pregnancy or performing preimplantation genetic testing (PGT). As the risk for an affected offspring is 50% in every pregnancy of an affected parent, prenatal, and preimplantation testing are of great importance. However, those procedures are associated with technical and ethical concerns. This chapter shortly reviews the common phacomatoses emphasizes their genetics and inheritance. We will review the common methods for prenatal and preimplantation diagnoses and discuss its use in common phacomatoses.

CONCLUSION

Phacomatoses are common autosomal dominant genetic conditions with variable expression. Ante-natal genetic diagnosis is an appropriate approach for family planning in individuals affected by phacomatosis or parents of an affected child.

Pränataldiagnostik – klassische Analytik mittels Chorionzottenbiopsie und Amniocentese

In diesem Artikel werden die Methoden der klassischen invasiven Pränataldiagnostik und die häufigsten, mittels konventioneller Zytogenetik diagnostizierten Chromosomenaberrationen beschrieben, um ihren, trotz der in anderen Beiträgen abgehandelten neuen Methoden, nach wie vor wichtigen Stellenwert herauszuheben.

Clinical investigation of chromosomal karyotype analysis in cells cultured from fetal bladder puncture liquid

The aim of this study was to investigate the feasibility of performing chromosomal karyotype analysis using cells cultured from fetal bladder puncture liquid (FBPL). Therefore, FBPL was extracted from 9 fetuses under ultrasonographic guidance, including 3 cases with fetal lower urinary tract obstruction (megabladder and oligohydramnios) and 6 cases with multiple malformations. The cells obtained from the FBPL were cultured in vitro for chromosome preparation and karyotype analysis. The cells from these 9 cases were all successfully cultured, and the chromosomal mitotic phases obtained could be used for counting and karyotype analysis. The gestational age ranged from 14 weeks and 2 days to 22 weeks, the amount of FBPL extracted was 30-55 ml, and the cell culture time ranged from 14 to 21 days. Eight cases in which the cells were subcultured exhibited 22-30 chromosomal mitotic phases, whereas 1 case without subculture showed 11 chromosomal mitotic phases. Cells obtained from the FBPL were successfully used for karyotype analysis following in vitro culture, thus demonstrating that prenatal fetal chromosome examination is possible in patients with a low gestational age, megabladder and oligohydramnios. These observations indicate that this technique has the potential to be used as a new prenatal diagnostic method.

Transcervical chorionic villus sampling: a practical guide

First trimester screening for fetal aneuploidies has made the implementation of diagnostic techniques essential. Chorionic villus sampling (CVS) is the method of choice for obtaining chorionic villi for molecular and cytogenetic analysis in the first trimester. Two techniques have been developed, a transcervical and a transabdominal. The selection criteria have been based historically on factors, such as placental location, parity, maternal weight and preference of the operator. In our institution, we developed an elevated level of expertise in the field of transcervical approach, resulting in good quality of samples and comparable fetal loss rate to other approaches. Despite three decades of transcervical CVS performance, little consensus in terms of its technique and clinical guidelines exists. Considering the expertise and the volume of procedures performed at our center, we suggest a practical clinical guideline for transcervical CVS.

Chromosomale Mosaike in der klinischen Zytogenetik

In der Zytogenetik werden Zellen im Gegensatz zu molekulargenetischen Untersuchungen individuell analysiert. Dadurch können Zellen mit verschiedenen Karyotypen (Zellmosaike) aufgedeckt werden. Dieser Beitrag gibt einen Überblick über die verschiedenen Probleme der diagnostischen Befunderhebung und -interpretation chromosomaler Mosaike. Eine besondere Herausforderung liegt darin, dass zwischen echten Mosaiken einerseits und Kulturartefakten, Pseudomosaiken, Alterseffekten, mütterlicher Kontamination oder Chimärismus andererseits unterschieden werden muss. Die Wahrscheinlichkeit, ein chromosomales Mosaik in der zytogenetischen Routinediagnostik zu übersehen, ist sehr hoch, da hier nur ca. 15 von 1012 Körperzellen und dazu in der Regel nur ein einziger Gewebetyp untersucht werden. Einige zytogenetische Mosaike sind typisch für bestimmte Syndrome, wie z. B. das Pallister-Killian-, das Katzenaugen oder das Ullrich-Turner-Syndrom; andere sind charakteristisch für bestimmte Krankheitsbilder, einschließlich hämatologischer maligner Erkrankungen.

Prenatal control of Hb Bart's disease in mainland China: can we do better?

The aim of the present study was to report a 3-year experience on the prenatal control of Hb Bart's (γ4) disease in Mainland China. All pregnancies with fetal Hb Bart's disease were included from January 2011 to December 2013. The main clinical characteristics of the affected pregnancies were reviewed, including maternal reproductive history, prenatal care in the current pregnancy, the gestation of pregnancy at the time of booking, the gestation at the time of prenatal diagnosis (PND), and the complications associated with the pregnancy. A total of 246 cases of fetal Hb Bart's disease were identified during the study period; among these, 177 (72.0%) were diagnosed in early gestation (≤24 weeks), and 69 (28.0%) in late gestation. Most (87.0%) of the patients presenting in late pregnancy had late or no prenatal care. Twenty (29.0%) had major obstetrical complications in patients presenting in late pregnancy, and five (5.0%) in patients presenting in relatively early pregnancy. The delay in PND deprived couples of opportunities to make informed decisions early in pregnancy. Efforts for designing and targeting strategies to improve the timeliness of prenatal care are urgently needed.

Chorionic villus sampling for early prenatal diagnosis: Experience at a mainland Chinese hospital

The aim of this study was to describe the experience of transabdominal chorionic villus sampling (CVS) at a mainland Chinese hospital. During a 7-year period, 1,172 pregnant women chose to have CVS for prenatal diagnosis. Details and outcome of all of these cases were reviewed. The median maternal age was 29 years (range 19-45). The median gestational age was 12 weeks (range 10-14). Fetal karyotyping and thalassaemia couples were the main indications (97.2%). Overall, 112 (9.7%) chromosomal abnormalities were identified. There were 91 (7.8%) major chromosomal abnormalities, including autosomal trisomy in 70 patients, sex chromosomal abnormalities in 17, triploidy in two and unbalanced chromosomal rearrangement abnormality in two. Additionally, 137 fetuses with severe thalassaemia syndrome were found, including 86 homozygous β-thalassaemia, and 51 homozygous α-thalassaemia or non-deletional haemoglobin H disease. The procedure failed to obtain an adequate sample in four (0.3%) patients. There were 229 pregnancies terminated for medical indications after CVS. There were three (0.3%) potentially procedure-related fetal losses. CVS is a safe and reliable prenatal diagnostic technique. It should be one of the options available to pregnant women who require prenatal diagnosis.

[Transabdominal chorionic villus sampling using biopsy forceps or needle: pregnancy outcomes by technique used]

OBJECTIVES

To compare pregnancy outcomes after transabdominal chorionic villus sampling using biopsy forceps or needle.

MATERIALS AND METHODS

Retrospective bicentric study including all women who had a transabdominal chorionic villus sampling between 2005 and 2009 (172 using biopsy forceps and 160 using needle). The primary endpoint was the rate of fetal loss, after excluding medical abortion due to the result of the biopsy. The secondary endpoint was the rate of premature rupture of the membrane. All cases were reviewed to try to determine the responsibility of the biopsy.

RESULTS

The pregnancy outcomes were not different between the two groups: 4 (4.4%) fetal losses in the biopsy forceps group and 6 (7.4%) in the needle group (P=0.52). Only one case (1.2%) of fetal loss can be attributed to the biopsy, using a needle, and none (0%) following a forceps biospy (P=0.29). The rate of premature rupture of the membrane was comparable in the two groups.

CONCLUSION

The pregnancy outcomes following chorionic villus sampling using a biopsy forceps or a needle seem comparable.

Structural chromosomal abnormalities detected during CVS analysis and their role in the prenatal ascertainment of cryptic subtelomeric rearrangements

Mosaic structural chromosomal abnormalities observed along the trophoblast-mesenchyme-fetal axis, although rare, pose a difficult problem for their prognostic interpretation in prenatal diagnosis. Additional issues are raised by the presence of mosaic imbalances of the same chromosome showing different sizes in the different tissues, that is, deletions and duplications in the cytotrophoblast and mesenchyme of chorionic villi (CV). Some of these cytogenetic rearrangements originate from the post-zygotic breakage of a dicentric chromosome or of the product of its first anaphasic breakage. Selection of the most viable cell line may result in confined placental mosaicism of the most severe imbalance, favoring the presence of the cell lines with the mildest duplications or deletions in the fetal tissues. We document three cases of ambiguous results in CV analysis due to the presence of different cell lines involving structural rearrangements of the same chromosome which were represented differently in the trophoblast and the mesenchyme. Observation by conventional karyotype of a grossly rearranged chromosome in one of the CV preparations (direct or culture) was crucial to call attention to the involved chromosomal region in other tissues (villi or amniotic fluid), allowing the prenatal diagnosis through molecular cytogenetic methods of subtelomeric rearrangements [del(7)(q36qter); del(11)(q25qter); del(20)(p13pter)]. This would have surely been undiagnosed with the routine banding technique. In conclusion, the possibility to diagnose complex abnormalities leading to cryptic subtelomeric rearrangements, together with a better knowledge of the initial/intermediate products leading to the final abnormal cryptic deletion should be added to the advantages of the CV sampling technique.

Reduced placental telomere length during pregnancies complicated by intrauterine growth restriction

Objectives

Recent studies have shown that telomere length was significantly reduced in placentas collected at delivery from pregnancies complicated by intrauterine growth restriction secondary to placental insufficiency. Placental telomere length measurement during ongoing pregnancies complicated by intrauterine growth restriction has never been reported. This was the main objective of our study.

Methods

In our center, late chorionic villus samplings were performed between 18 and 37 weeks of amenorrhea in 24 subjects with severe intrauterine growth restriction (cases) and in 28 subjects with other indications for prenatal diagnosis (controls). Placental insufficiency was assessed by histo-pathological examination. Relative measurement of telomere length was carried out prospectively by quantitative Fluorescent In Situ Hybridization using fluorescent Peptide Nucleic Acid probes on interphase nuclei obtained from long-term cultured villi and with an automated epifluorescent microscope. A quantitative Polymerase Chain Reaction technique was performed to confirm the quantitative Fluorescent In Situ Hybridization results. The number of copies of gene loci encoding the RNA template (hTERC) and the catalytic subunit (hTERT) of the enzyme complex telomerase were also estimated in these placentas by Fluorescent In Situ Hybridization.

Results

Mean fluorescence intensity of telomere probes estimated by quantitative Fluorescent In Situ Hybridization was significantly less for cases compared to controls (p<0.001). This result indicated that mean telomere length was significantly reduced in placentas during pregnancies complicated by intrauterine growth restriction. Reduced telomere length was confirmed by the quantitative Polymerase Chain Reaction technique. No copy number variation of the hTERC and hTERT loci was noticed for cases, or for controls.

Conclusion

This study clearly demonstrates a reduction of placental telomere length in ongoing pregnancies (from 18 to 37 weeks of amenorrhea) complicated by severe intrauterine growth restriction secondary to placental insufficiency.

[Feasibility of chorionic villous sampling outside a prenatal diagnosis center]

OBJECTIVES

According to new recommendations, a high combined risk for Down syndrome in the first trimester of pregnancy must indicate the need for a prenatal diagnosis. This is possible thanks to chorionic villous sampling. The objective of our study was to show that chorionic villous sampling is achievable in everyday practice, even outside research centers for pre-natal diagnosis.

PATIENTS AND METHODS

It was a descriptive, retrospective study. All the patients who underwent a chorionic villous sampling in our level II maternity center from November 2005 to September 2009 were included. Success and complications rates linked with the procedure were calculated.

RESULTS

One hundred and fourteen pregnancies were included. A definitive diagnosis was given in 98.25% of cases. A secondary amniocentesis was necessary in 1.75% of cases. A medical termination of the pregnancy was done in 18.42% of cases. Without accounting for underlying pathology, fetal loss rate was up to 5.75%. Only one case of unexpected fetal loss was noted (1.15% of the ongoing pregnancies).

CONCLUSION

Our study shows that the presence of trained professional allows for onsite performance chorionic villous sampling.

[Maze-like vascular anomaly in partial mole. Interest for the pathological diagnosis of partial mole on chorionic villous sampling]

A case of maze-like angiomatoid anomaly in villi obtained by chorionic villous sampling (CVS) is described. This feature is pathognomonic of partial mole (triploid syndrome) and it was later confirmed by chromosomal analysis. Maze-like angiomatoid anomaly was previously described on specimen submitted after spontaneous or induced abortions, but it was never reported on CVS. This report emphasized that microscopic investigation of CVS cannot be conclusive for cytogenetic anomaly in almost all cases excepted for partial mole where diagnosis criteria are usually characteristic.

A randomized study to assess two different techniques of aspiration while performing transabdominal chorionic villus sampling

OBJECTIVE

The technique used to perform transabdominal chorionic villus sampling (CVS) is not standardized, but aspiration of villi is generally obtained by discontinuous vacuum created in a syringe, manually or by a hand-grip device. We evaluated the feasibility of a new method of performing CVS which employs a 4-mL Vacutainer connected to the needle, producing a continuous negative pressure.

METHODS

Two hundred pregnant women, whose gestational age ranged from 10 + 2 to 16 + 2 (mean, 12 + 1) weeks, entered the randomized study, which was powered to detect with 90% probability the absence of any difference in the size of chorionic samples obtained by using a 20-mL syringe with the vacuum obtained by a hand-grip device (Group 1) or by a vacutainer (Group 2). Four operators with different levels of experience performed all the procedures, which were done transabdominally using a freehand technique with a 20-gauge needle under ultrasound guidance.

RESULTS

Maternal age, body mass index, gestational age and the way the needle was inserted within the chorion were similar in the two groups. The median amount of villi sampled was 20 mg, with no differences between the two groups. The rate of fetal loss was 1.7%. All losses occurred in women of Group 1 who had only one needle insertion. A second needle insertion was required more frequently while using the vacutainer.

CONCLUSION

This new technique for performing transabdominal CVS uses a readily available device and is as effective as traditional sampling systems to aspirate villi. It has the advantage of being a one-operator procedure.

Pain experience during chorionic villus sampling and amniocentesis: A preliminary study

OBJECTIVE

To investigate the maternal perception of pain before and after amniocentesis (AC) or transabdominal chorionic villus sampling (TA-CVS).

STUDY DESIGN

Three hundred women were divided into groups of 100 participants destined to undergo three different fetal sampling procedures: amniocentesis (group 1), transabdominal chorionic villus sampling (CVS) with a 19 gauge Blache needle (group 2) and transabdominal CVS with a 20 gauge needle (group 3). The visual analog scale (VAS) was used to quantify the patient's pre-sampling expected pain level and the real pain level was measured immediately after the sampling procedure. The factors liable to influence the VAS score after the sampling procedure were studied by single and multivariate analysis and concerned either the sampling procedure or patient demographic data.

RESULTS

The VAS scores obtained before the procedure were not significantly different for the three sampling groups. When performed with a 19 gauge Blache needle TA-CVS is significantly more painful than the other sampling procedures (p=0.0002): VAS score of 3.62 (group 2), 2.49 (group 3) and 2.68 (group 1) for CVS with 20 gauge needle and amniocentesis. Multivariate analysis identified a group of patients for which the perception of pain induced by sampling was higher compared to the other patients: nulliparous patients, having undergone 19 gauge Blache needle CVS, with a high pre-sampling VAS score.

CONCLUSION

Transabdominal chorionic villus sampling with a 19 gauge Blache needle seems to be the most painful sampling procedure. We question the need to use a 19 gauge needle as acceptable results are obtained with a 20 gauge needle.

Procedure-Related Complications of Amniocentesis and Chorionic Villous Sampling

OBJECTIVE

To compile a systematic review of complications related to genetic amniocentesis and chorionic villus sampling (CVS) to provide benchmark data for counseling and performance assessment of individual operators.

DATA SOURCES

We searched the MEDLINE database for articles published after January 1, 1995, that reported data for at least 100 women with singleton pregnancies with genetic amniocentesis after 14 weeks of pregnancy and reports of CVS carried out transabdominally between 10 and 14 weeks.

METHODS OF STUDY SELECTION

For amniocentesis, 29 articles fulfilled search criteria. Sixteen studies fulfilled search criteria for CVS.

TABULATION, INTEGRATION, AND RESULTS

After genetic amniocentesis, pooled pregnancy loss within 14 days was 0.6% (95% confidence interval [CI] 0.5-0.7), rising to 0.9% (95% CI 0.6-1.3) for pregnancy loss before 24 weeks and 1.9% (95% CI 1.4-2.5) for total pregnancy loss. Corresponding figures for CVS were 0.7%, 1.3%, and 2%. The data on multiple insertions showed large heterogeneity, ranging from 0.2% to 2.9% for amniocentesis (pooled risk 2.0%, 95% CI 0.9-3.6) and from 1.4% to 26.6% for CVS (pooled risk 7.8%, 95% CI 3.1-14.2). Only five amniocentesis studies provided controls, but none was matched for gestational age. Pooled relative risks for fetal loss before 28 weeks and total pregnancy loss were 1.46 (95% CI 0.86-2.49) and 1.25 (95% CI 1.02-1.53), respectively.

CONCLUSION

Although the risks of pregnancy loss are relatively low, lack of adequate controls tends to underestimate the true added risk of prenatal invasive procedures.

[Abnormal placental caryotype in severe intrauterine growth retardations (IUGR). Case report]

Except for cases due to maternal hypertension, severe and early intrauterine growth retardations are most usually due to fetal abnormalities. We report a case of confined placental homogenous tetraploidy associated with major fetal growth retardation leading to the premature delivery of a life born baby with a normal caryotype. We discuss the interest of chorionic villus sampling in cases of unexplained severe fetal growth retardation.

Chorionic villus sampling for beta-thalassemia: the first report of experience in Iran

OBJECTIVES

Beta-thalassemia is one of the most common hereditary disorders in Iran. The prenatal diagnosis of beta-thalassemia is part of a control program in our country and it began 13 years ago. During the past 8 years the number of procedures has increased significantly as also the legal abortions. This is the first report made on the CVS program in Iran.

MATERIALS AND METHODS

One thousand six hundred and sixty-one cases of transabdominal Chorionic Villus Sampling (CVS) have been retrospectively evaluated. Among them 1381 cases had inclusion criteria. CVS results, complications and fetal loss rate were evaluated. The distributions of the population at risk were divided between eight regions that have been proposed for beta-thalassemia mapping previously.

RESULTS

The mean age of the patients was 26.2 +/- 5.2 years with mean gestational age of 11.4 +/- 1.4 weeks. CVS was successful in all the patients (100%) although 1% required a second procedure. Post CVS fetal loss was 1.45%. Other minor complications were bleeding or spotting (1.81%), amniotic fluid leak (0.5%), small sub-chorionic hematoma (0.58%), severe abdominal pain (0.6%) and severe vasovagal reaction (0.14%). Late complications were seen in 0.21% (oligohydraminos). Approximately 2/3 of the patients were referred from three regions of the country, North (26.8%), South West (22.4%), Central (19.5%) and the remainder (31.3%) were from the other five regions.

CONCLUSION

CVS is a safe and effective method for prenatal diagnosis of beta-thalassemia in countries with a high prevalence as in Iran. The overall complication rate is quite low and acceptable. Fortunately the recent acceptance of legal abortion with respect to Muslim rules has increased the effectiveness of the procedure and made great advances in its application in Iran. Correspondingly, social knowledge has also improved but still there is a gap between the population at risk and the required prenatal diagnosis laboratories and sampling centers.

(Potential) false-negative diagnoses in chorionic villi and a review of the literature

OBJECTIVES

To assess the incidence of (potential) false-negative findings of cytogenetic diagnosis in STC-villi and/or LTC-villi and to determine the best strategy for karyotyping chorionic villi in order to avoid false-negative results.

METHODS

2476 chorionic villus samples were received for prenatal cytogenetic investigations. Karyotyping was routinely performed on STC- and LTC-villi preparations by G-banding. Fluorescence in situ hybridization (FISH) analyses were performed in addition to standard chromosome analysis when necessary. Sometimes follow-up investigations like amniocentesis were performed before a definite prenatal cytogenetic result could be reported.

RESULTS

In 2389/2476 (96.5%) of the cases, both STC- and LTC-villi were investigated. Normal STC- with abnormal LTC-villi results and finally an abnormal fetal karyotype were detected in ten cases (10/2389; 0.42%); in 9/10 of the cases the indication was fetal ultrasound abnormalities. Normal STC- and LTC-villi and finally an abnormal fetal karyotype were detected in two cases (2/2389; 0.08%).

CONCLUSION

The most reliable technique for prenatal diagnosis after chorionic villus sampling (CVS) is the combination of the analysis of both STC- and LTC-villi to reduce the incidence of false-negative findings to a minimum. In the case of fetal ultrasound abnormalities with a small amount of villi available, the investigation of LTC-villi is recommended over that of STC-villi.

Health and developmental outcome of children following prenatal diagnosis of confined placental mosaicism

OBJECTIVE

To determine the long-term health and development of a cohort of children in whom confined placental mosaicism (CPM) was diagnosed at prenatal diagnosis.

METHODS

A retrospective cohort study was performed comparing 36 children in whom CPM had been diagnosed prenatally with 195 controls subjects in whom a normal karyotype had been detected prenatally. Data comprising birth information, health, health service utilisation, growth, development, behaviour, and the family were collected by a maternal questionnaire administered when the subjects were aged between 4 and 11 years.

RESULTS

CPM cases did not differ from controls across a broad range of health measures and there were no major health problems or birth defects among the CPM group. No increase was detected in the incidence of intrauterine growth retardation (IUGR) among CPM cases; however, postnatal growth was reduced compared with controls (p = 0.047). Development and behaviour in CPM cases was similar to that of controls.

CONCLUSIONS

The prenatal diagnosis of CPM is not associated with an increased risk of birth defects or developmental problems, but may be associated with decreased growth.

Chorionic villus sampling and amniocentesis

PURPOSE OF REVIEW

The advantages and disadvantages of common invasive methods for prenatal diagnosis are presented in light of new investigations.

RECENT FINDINGS

Several aspects of first-trimester chorionic villus sampling and mid-trimester amniocentesis remain controversial, especially fetal loss rate, feto-maternal complications, and the extension of both sampling methods to less traditional gestational ages (early amniocentesis, late chorionic villus sampling), all of which complicate genetic counseling. A recent randomized trial involving early amniocentesis and late chorionic villus sampling has confirmed previous studies, leading to the unquestionable conclusion that transabdominal chorionic villus sampling is safer. The old dispute over whether limb reduction defects are caused by chorionic villus sampling gains new vigor, with a paper suggesting that this technique has distinctive teratogenic effects. The large experience involving maternal and fetal complications following mid-trimester amniocentesis allows a better estimate of risk for comparison with chorionic villus sampling.

SUMMARY

Transabdominal chorionic villus sampling, which appears to be the gold standard sampling method for genetic investigations between 10 and 15 completed weeks, permits rapid diagnosis in high-risk cases detected by first-trimester screening of aneuploidies. Sampling efficiency and karyotyping reliability are as high as in mid-trimester amniocentesis with fewer complications, provided the operator has the required training, skill and experience.