Prenatal diagnosis by chorionic villus sampling: lessons of the first 600 cases

Discordant structural chromosomal aberrations in chorionic villi and amniotic fluid leading to a formation of an isochromosome 21: a case report

Background

Fetoplacental discrepancies occur in approximately 1–2% of analyzed prenatal cases. They are typically due to confined placental mosaicism, where an aberration is observed in the placental cells but not found in the fetal cells. Confined placental mosaicism usually involves aneuploidies and more sparsely structural chromosomal aberrations. To the best of our knowledge, this is the first reported case of a discrepancy in the analyses of chorionic villus sampling and amniocentesis involving two different structural chromosomal aberrations of chromosome 21.

Case presentation

We report a 33-year-old woman who was referred for a non-invasive prenatal testing due to an increased risk of trisomy 21 gleaned from a combined ultrasound and blood test. The non-invasive prenatal testing showed an increased risk of trisomy 21 with a normalized coverage signal that did not match the fetal cell-free DNA fraction. Rapid aneuploidy detection performed on uncultured chorionic villi indicated mosaicism for trisomy 21. The follow-up analyses revealed discordant chromosomal aberrations: 46,XY,der(21)t(10;21)(p11.21;q10) in the analysis of the chorionic villus sampling and 46,XY, + 21,der(21;21)(q10;q10) in the analysis of the amniocentesis. Thus, the analyses indicated mosaicism for a cell line containing trisomy 21 and a cell line containing a partially duplicated short arm of chromosome 10 in the chorionic villi and complete trisomy 21 resulting from an isochromosome 21 in the amniotic fluid. The analyses of the lymphocytes and the fibroblasts of the woman were normal.

Conclusions

We propose a multiple-step mechanism as a possible theoretical explanation for the formation of these discordant structural chromosomal aberrations in the chorionic villi and amniotic fluid. With this case report, we want to highlight the importance of understanding the possible underlying embryological mechanisms when interpreting results from different prenatal analyses.

Invasive prenatal diagnostic techniques

Subspecialization in fetal medicine has expanded the scope for obstetricians to investigate the fetus and its surrounding environment in greater detail. Of the advances in technology that have made this possible, ultrasonography is the most important. A high degree of skill is required if it is to be applied to the performance of invasive diagnostic techniques. These should be performed only in specialized centres with appropriate facilities and an adequate referral base. However, it is important for obstetricians to know what is possible in the field of prenatal diagnosis and therapy in order to give patients the best advice.

Forty years of obstetric ultrasound 1957-1997: from A-scope to three dimensions

In this article, we record the history of obstetric ultrasound as it developed worldwide in the second half of the twentieth century. The technological advances during this period saw the evolution of equipment from the original adapted metal flaw detectors producing a simple A-scan to the modern, purpose built, real-time colour flow machines with three-dimensional capability (Fig. 1). Clinically, ultrasound began as a research tool, but the poor quality of the images led to the ridicule of many of the early investigators. However, because of their perseverance, ultrasound developed into an imaging modality providing immense diagnostic capabilities and facilitating with precision many invasive procedures, diagnostic and therapeutic, both of which have made significant contributions to patient care. In this history, we recall the people, the personalities, and the problems they encountered during the development of ultrasound and how these problems were resolved, so that ultrasound now is available for use in the care of pregnant women throughout the developed world.

Chorionic villus sampling

Chorionic villus sampling (CVS) has been used a successful and safe first-trimester prenatal diagnostic technique for over 12 years. Developed to avoid the medical and psychological complications of later prenatal diagnosis by amniocentesis, CVS rapidly has become a primary tool for the diagnosis of fetal cytogenetic, molecular, and biochemical disorders. In addition, its development has led to an improved understanding of several biological processes, including confined placental mosaicism and uniparental disomy.

Experience with 1251 transcervical chorionic villus samplings performed in the first trimester by a single team of operators

OBJECTIVE

We report our experience with 1251 chorionic villus samplings (CVS) performed by a single team of operators.

STUDY DESIGN

From April 1984 through August 1993, 1251 CVS were performed in 1236 pregnancies. The transcervical route was used in the vast majority and the sampling was performed during the 9th through 13th weeks of gestation in 1193 cases (96%). Follow-up was ensured to tabulate the pregnancy-related complications and fetal loss rate until 28 weeks' gestation. Pregnancy outcome was documented for all but 36 women (3%).

RESULTS

Most of the tests (72%-891/1236 pregnancies) were performed for advanced maternal age (> or = 35 years). The percentage of each indication remained relatively stable, around 90% for chromosomal indications and between 8 and 11% for DNA studies. Samples adequate for diagnosis were obtained in one or two sessions in 1179 pregnancies (95%). The rate of spontaneous abortion possibly related to CVS was 2.5% (28/1092). Mosaicism confined to the placenta was found in 23 cases (1.8%). The pregnancy outcome was known in 1098 pregnancies. There were 10 perinatal losses (0.9%) and nine congenital malformations (0.8%). No transverse limb defects were observed. The rate of premature deliveries (4.6%) and of small for gestational age were comparable to the general uninstrumented population.

CONCLUSION

CVS is a safe and effective mode of antenatal diagnosis when performed by a single team of experienced operators.

The predictive value of cytogenetic diagnosis after CVS based on 4860 cases with both direct and culture methods

Cytogenetic analysis was performed in 4860 chorionic villus samples by means of both direct preparation and long-term culture. The results of the analysis were compared with a classification including all theoretical types of combinations between the chromosomal constitution of the cytotrophoblast, extraembryonal mesoderm, and fetus, with the aim of evaluating the cytogenetic variability along the trophoblast-embryo axis. Eighteen of 29 possible combinations were found demonstrating a considerable heterogeneity. A mosaic conceptus was found in 1.5 per cent of cases, with generalized mosaicisms and confined mosaicisms in 0.2 and 1.3 per cent, respectively. Cytogenetic variability along the trophoblast-embryo axis was found in 1.42 per cent of cases. Results possibly leading to diagnostic errors (false-positive and false-negative results) were found in only 1.38 per cent. False-positive results of direct preparation were the most commonly observed discrepancy (0.8 per cent), while the incidence of false-positive results of the culture method and of both methods was 0.31 and 0.16 per cent respectively. The incidence of false-negative results was 0.1 per cent, with false-negative results of direct preparation 0.08 per cent and false-negative results of both methods 0.02 per cent. False-negative results of the culture method were not found. Our data confirm the high diagnostic accuracy of chorionic villus sampling and the utility of the combined use of the two methods in minimizing diagnostic errors and in reducing the need for follow-up amniocentesis.

Organization of the human CD40L gene: implications for molecular defects in X chromosome-linked hyper-IgM syndrome and prenatal diagnosis

Recently, CD40L has been identified as the gene responsible for X chromosome-linked hyper-IgM syndrome (HIGM1). CD40L on activated T cells from HIGM1 patients fails to bind B-cell CD40 molecules, and subsequent analysis of CD40L transcripts by reverse transcription PCR demonstrated coding region mutations in these patients. This approach, however, is of limited use for prenatal diagnosis of HIGM1 in the early-gestation fetus. In this report, we have defined the genomic structure of the CD40L gene, which is composed of five exons and four intervening introns. With this information, we have defined at the genomic level the CD40L gene abnormalities for three previously described HIGM1 patients who demonstrated clustered deletions in the CD40L coding region. These different deletions arose from three distinct mechanisms, including (i) a splice donor mutation with exon skipping, (ii) a splice acceptor mutation with utilization of a cryptic splice site, and (iii) a deletion/insertion event with the creation of a new splice acceptor site. In addition, we have performed prenatal evaluation of an 11-week-old fetus at risk for HIGM1. CD40L genomic clones provide a starting point for further studies of the genetic elements that control CD40L expression. Our knowledge of the CD40L gene structure will prove useful for the identification of additional mutations in HIGM1 and for performing genetic counseling about this disease.

Cytogenetic results from the U.S. Collaborative Study on CVS

Cytogenetic data are presented for 11,473 chorionic villus sampling (CVS) procedures from nine centres in the U.S. NICHD collaborative study. A successful cytogenetic diagnosis was obtained in 99.7 per cent of cases, with data obtained from the direct method only (26 per cent), culture method only (42 per cent), or a combination of both (32 per cent). A total of 1.1 per cent of patients had a second CVS or amniocentesis procedure for reasons related to the cytogenetic diagnostic procedure, including laboratory failures (27 cases), maternal cell contamination (4 cases), or mosaic or ambiguous cytogenetic results (98 cases). There were no diagnostic errors involving trisomies for chromosomes 21, 18, and 13. For sex chromosome aneuploidies, one patient terminated her pregnancy on the basis of non-mosaic 47,XXX in the direct method prior to the availability of results from cultured cells. Subsequent analysis of the CVS cultures and fetal tissues showed only normal female cells. Other false-positive predictions involving non-mosaic aneuploidies (n = 13) were observed in the direct or culture method, but these cases involved rare aneuploidies: four cases of tetraploidy, two cases of trisomy 7, and one case each of trisomies 3, 8, 11, 15, 16, 20, and 22. This indicates that rare aneuploidies observed in the direct or culture method should be subjected to follow-up by amniocentesis. Two cases of unbalanced structural abnormalities detected in the direct method were not confirmed in cultured CVS or amniotic fluid. In addition, one structural rearrangement was misinterpreted as unbalanced from the direct method, leading to pregnancy termination prior to results from cultured cells showing a balanced, inherited translocation. False-negative results (n = 8) were observed only in the direct method, including one non-mosaic fetal abnormality (trisomy 18) detected by the culture method and seven cases of fetal mosaicism (all detected by the culture method). Mosaicism was observed in 0.8 per cent of all cases, while pseudomosaicism (including single trisomic cells) was observed in 1.6 per cent of cases. Mosaicism was observed with equal frequency in the direct and culture methods, but was confirmed as fetal mosaicism more often in cases from the culture method (24 per cent) than in cases from the direct method (10 per cent). The overall rate of maternal cell contamination was 1.8 per cent for the culture method, but there was only one case of incorrect sex prediction due to complete maternal cell contamination which resulted in the birth of a normal male.(ABSTRACT TRUNCATED AT 400 WORDS)

Placental mosaicism in a case of 46,XY,-22,+t(22;22)(p11;q11) or i(22q) diagnosed at amniocentesis

46,XY,-22,+t(22;22)(p11;q11) or i(22q) was diagnosed in 15/15 cells from two cultures from the amniotic fluid culture of a 31-year-old patient whose fetus demonstrated cystic hygroma on ultrasound. Cytogenetic studies performed on fetal skin from the abortus revealed the same karyotype as that seen on amniocentesis, but the placenta demonstrated a 46,XY/46,XY,-22,+t(22;22) or i(22q) mosaicism, with 65 per cent of the cells being 46,XY. This case provides an example of placental mosaicism for a normal male karyotype, while the fetus demonstrated non-mosaic trisomy 22.

Outcome of 1500 consecutive chorionic villus samplings

OBJECTIVE

To evaluate the clinical complications and diagnostic problems of chorionic villus sampling.

DESIGN

A pragmatic retrospective analysis.

SETTING

Tertiary obstetric referrals mostly to private practice; sampling carried out at Royal Prince Alfred Hospital; diagnostic analysis usually at Oliver Latham Laboratory, or the Clinical Immunology Research Centre, Royal Prince Alfred Hospital, New South Wales.

PATIENTS

1500 women in the first trimester of pregnancy requesting prenatal diagnosis because of a risk of chromosomal or inherited genetic disorder in the fetus.

INTERVENTIONS

Ultrasound-guided passage of a catheter into the chorion through the cervix.

MAIN OUTCOME MEASURES

Incidence of unintended abortion, preterm births, low weight infants and discrepant karyotypes.

RESULTS

There were 42 unintended abortions (3.0%), about 0.4% higher than the background abortion rate in women of similar age. Abortion did not occur more frequently in women with vaginal bleeding earlier in that pregnancy. Rates of preterm births and birth of low birthweight infants did not differ from the general population. A second diagnostic test was required in 68 women (4.5%). Mosaicism and tetraploidy were usually confined to the chorion.

CONCLUSION

Chorionic villus sampling is an acceptable diagnostic test. Amniocentesis should be offered to patients who show mosaicism or tetraploidy.

Comparison of transabdominal and transcervical CVS and amniocentesis: sampling success and risk

A total of 2931 women randomized to either transabdominal CVS, transcervical CVS, or amniocentesis were studied. Unless intended or unintended abortion had occurred, they had completed up to 28 weeks of pregnancy. No significant difference was seen between total fetal loss in the transabdominal CVS group and the amniocentesis group (6.5 and 6.8 per cent, respectively, SE difference = 0.92 per cent, p = 0.01). The total fetal loss in the transcervical CVS group was 10.1 per cent. After pooling our data with data from the Canadian randomized study and the American non-randomized study, the difference in risk between transcervical CVS and amniocentesis was 1.8 per cent (SE difference = 0.64 per cent, p = 0.8). When the number of failed procedures and those cases evaluated as unfeasible for the assigned method--for anatomical reasons--are compared, the overall sampling efficacy is poorer transcervically than transabdominally.

Single-center comparison of results of 1000 prenatal diagnoses with chorionic villus sampling and 1000 diagnoses with amniocentesis

Large multicenter studies have confirmed the safety and accuracy of chorionic villus sampling as a prenatal genetic diagnostic procedure, but there have been few single-center evaluations. We report our experience with 1000 consecutive chorionic villus sampling procedures compared with 1000 consecutive amniocentesis procedures during the same period. The procedures were performed by the same genetic counselors, sonographers, obstetricians, and laboratory personnel. Indications for referral, demographic characteristics of patients, numbers of attempts per patient, fetal loss rates, laboratory results, and evaluation of accuracy are included. Analysis of all data suggests that chorionic villus sampling is a safe and accurate alternative to amniocentesis in our community-based teaching hospital.

Risk of miscarriage after transcervical and transabdominal CVS in relation to bacterial colonization of the cervix

Cervico-genital colonization with micro-organisms poses a potential threat to the pregnancy when transcervical (TC) CVS is performed. In order to evaluate this threat, cervical swabs in 478 patients were obtained and cultured for bacteria, yeasts, and mycoplasmas; chlamydias were detected by an enzyme immunology test. Two hundred and seventy-one patients had CVS done transvaginally and 207 underwent transabdominal (TA) CVS. Transvaginal specimens were obtained in 61.6 per cent by forceps biopsy. Overall in 29.9 per cent of patients micro-organisms were detected, the rate and distribution of different species being the same in both groups. There were 36 (7.5 per cent) miscarriages up to 28 weeks of gestation in the combined groups, 29 (10.7 per cent) in the TC-CVS group and 7 (3.4 per cent) in the TA-CVS group. When miscarriages occurred after TC-CVS, bacteria/yeasts were involved in 10.3 per cent of cases and mycoplasmas in 37.9 per cent, this proportion being almost the same in early (less than 2 weeks) and late (greater than 2 weeks) miscarriages. After TA-CVS, in 28.6 per cent only mycoplasmas, and this only in late miscarriages (greater than 2 weeks), were involved, accounting for 40 per cent of late miscarriages.

Patterns of mood states in pregnant women undergoing chorionic villus sampling or amniocentesis

The purpose of this study was to compare patterns of self-reported mood states of women having chorionic villus sampling (CVS) (n = 151) to those of women electing amniocentesis (n = 30) with the indication of advanced maternal age. Mood states were defined as scores on the 6 subscales of the Profile of Mood States (POMS). Women at 4 U.S. prenatal diagnostic facilities completed the POMS at 4 assessment periods. These were a) at their initial genetic counseling session, b) 2 weeks post CVS results (or an equivalent time), c) 2 weeks post amniocentesis results (or an equivalent time), and d) at 30 weeks gestation. Repeated measures analysis of variance revealed that anxiety, fatigue, and confusion decreased, and vigor increased in both groups as the pregnancy progressed. Depression decreased in both groups and then increased at assessment 4 in women in the amniocentesis group but not in those electing CVS. Results should be interpreted in conjunction with obstetrically and genetically-oriented findings regarding safety and accuracy to help women decide between the 2 procedures.

Transcervical chorionic villus sampling and amniocentesis: a comparison of reliability, culture findings, and fetal outcome

We evaluated the reliability, culture findings, and fetal outcome after transcervical chorionic villus sampling or amniocentesis in a group of 860 patients. All procedures were performed for the indication of advanced maternal age with consistent procedure and laboratory techniques. Successful procedures were completed in 97.7% (420/430) of patients in the chorionic villus sampling group, compared with 99.5% (428/430) in the amniocentesis group (p less than 0.01). Success was more frequent with only one attempt in the amniocentesis group (427/428) versus 354 of 420 in the chorionic villus sampling group (p less than 0.001). Culture failure was more common after chorionic villus sampling (p less than 0.001). Pregnancy loss rates through 28 weeks' gestation and the entire gestation were not significantly different. The prevalence of preterm delivery did not vary between groups, but birth weights of infants in the chorionic villus sampling group were significantly greater. In summary, the present investigation supports previous findings that chorionic villus sampling is a safe alternative to amniocentesis and is not associated with long-term pregnancy complications.

Down syndrome

Down syndrome is the most common chromosome abnormality of man. The isolated occurrence of any one of the most of the protean systemic and ocular features of Down syndrome is not specific to the disorder. The associated occurrence of several of these features, however, has distinguished affected individuals as having a distinct entity for nearly 125 years. Recent advances in prenatal diagnosis have allowed the earlier detection, in utero, of chromosomal abnormalities. Although predisposing genetic and environmental influences remain for the most part unknown, advances in molecular biology are leading to a greater understanding of other common disorders that occur with an increased incidence in individuals with Down syndrome; these include Alzheimer's disease, acute childhood leukemia, congenital heart malformations, and immunologic abnormalities. Associated ocular disorders can significantly affect the quality of life of individuals with Down syndrome. As more children with Down syndrome live into adulthood, the ophthalmologist will play an increasing role in allowing them to lead productive and meaningful lives.

Cytogenetic results of chorionic villus sampling: high success rate and diagnostic accuracy in the United States collaborative study

Cytogenetic results of first-trimester chorionic villus sampling are reported from seven U.S. medical centers. For 6033 patients who had a successful chorionic villus sampling procedure, the rate for obtaining a cytogenetic diagnosis was 99.6% with the direct method, long-term culture, or both. There were no incorrect sex predictions and no diagnostic errors involving trisomies 21, 18, or 13, sex chromosome aneuploidies, or structural abnormalities. There were no cases of normal cytogenetic diagnosis followed by birth of a cytogenetically abnormal infant. Three cases of unusual aneuploidies (tetraploidy, trisomy 16, and trisomy 22) detected by the direct method only were not confirmed by cytogenetic follow-up. Mosaic cytogenetic abnormalities were observed in 0.83% of all cases in which chorionic villus sampling was done but were confirmed by amniocentesis or in fetal tissues in only 7 of 30 cases (23.3%). Maternal cell contamination occurred in 1.9% of long-term cultures, although this did not present any cytogenetic diagnostic difficulties. Overall, a very high degree of laboratory success and diagnostic accuracy was observed with either cytogenetic method, although fewer predictive errors were observed with the long-term culture method and none were observed when both methods were used.

The predictive value of cytogenetic diagnosis after CVS: 1500 cases

The cytogenetic results of 1500 chorionic villus samples (CVS) are presented. In these 1500 samples, 23 samples (1.5 per cent) could not be provided with a diagnosis because of laboratory failure. This failure rate dropped from 3 per cent in the first 500 samples to 0.2 per cent in the last 500. In the remaining 1477 samples, 58 (3.9 per cent) chromosomal aberrations were found. Of these, 21 (36 per cent) proved not to represent the karyotype of the fetus proper. Predictive values of (different groups of) chromosomal aberrations in CVS are calculated. The impact of (differences between) the predictive value for some major chromosomal aberrations is discussed. A tissue- and chromosome-specific selection mechanism is postulated.

Fetal loss rate after chorionic villus sampling and subsequent amniocentesis

Here we review a group of 82 patients who underwent both chorionic villus sampling (CVS) and amniocentesis in the same pregnancy during the period May 1984-May 1988. A fetal loss rate of 2.5% is documented. This is not essentially different from the sum of fetal loss rates following each of the procedures separately (CVS, 1.9%; amniocentesis, 1.0%) established during the same period.

The European collaborative study on mosaicism in chorionic villus sampling: data from 1986 to 1987

Data on a total of 11,855 diagnostic chorionic villus samples obtained in the years 1986 and 1987 were compiled from a questionnaire filled in by 36 European cytogenetic centres. Mosaicism was reported in 141 cases. The cytogenetic findings were followed by induced abortion in 24 cases. Spontaneous abortion was observed in nine mosaic pregnancies, a rate not significantly different from that observed for CVS in total. Mosaicism was found in 1.2 per cent of analyses by direct analysis/short-term culture, in contrast to the 0.6 per cent found after long-term culture. Evidence for fetal non-mosaicism was found in 99 of the 141 cases. The finding of mosaicism in first-trimester CVS should always elicit further analyses, preferably after amniocentesis, to substantiate the suspected fetal chromosome aberration.

The value of routine cervical cultures before transcervical chorionic villus sampling

In 226 women requesting chorionic villus sampling (CVS), routine cervical cultures were obtained before the procedure. Transcervical CVS was performed irrespective of the test results. The prevalence of potential pathogens in cervical cultures at our institution is low. Beta haemolytic Streptococcus was cultured in 3 per cent of the women. No pathogenic microorganisms were isolated in 64 per cent of the women. There was no relationship between culture results and the outcome of pregnancy. These observations suggest that adequate antiseptic cleansing of the genital tract is a suitable approach and there is no need to routinely perform cultures before CVS.

Trisomy 16 detected at chorion villus sampling

Trisomy 16 detected at chorion villus sampling (CVS) may reflect the placental but not the fetal karyotype. We describe a case in which the pregnancy continued until intrauterine death at 37 weeks. Cytogenetic study of two placental samples showed 47, + 16 and 46,XX; the fetus was morphologically grossly normal, but fetal tissue culture was unsuccessful. Conservative management may be appropriate when trisomy 16 is detected at CVS and the pregnancy is normal ultrasonographically.

Investigations of chorionic villi after chorionic villus sampling (CVS). Correlation of morphological with clinical and laboratory data

This report documents the first 262 cases of chorionic villus sampling (CVS) performed in parallel with cytogenetic and morphological investigations. Histomorphological examination of these CVS specimens gave suitable results in about 96% (251 cases). Of the latter, 201 samples (80.1%) exhibited villi and 176 (70.1%), maternal tissue. Viability and maturation of the chorionic villi were determined light microscopically even in cases with few villus trees. Smooth avascular villi with poorly defined margins observed under an inverted microscope, less than 10 mitoses after short-term incubation, and reduced growth of cell cultures were significantly correlated with sampling at the chorion laeve by means of histomorphologic criteria. Villi from cases exhibiting cytogenetically proved chromosomal abnormalities were characterized by molar degeneration or stromal fibrosis, or both, in 4 out of 9 cases, including 3 mosaics. In early abortions (within 3 weeks after CVS), an unexpectedly high rate of pathohistological changes within maternal tissue was evident. These results need further confirmation by investigation of a greater number of samples with immunohistochemical and morphometric methods.

Identification of carriers of Duchenne muscular dystrophy: value of molecular analysis

Currently, molecular methods are the most accurate diagnostic tools for carrier detection and prenatal diagnosis of Duchenne muscular dystrophy (DMD). This report illustrates the value of molecular diagnosis as opposed to previous diagnostic methods, the need for frequent re-evaluations as new methodologies develop, and the necessity for in-depth genetic counseling. In Family 1, the proposita was predicted to be a carrier by an indirect assay (abnormal in vitro muscle ribosomal protein synthesis). DNA analysis using restriction fragment length polymorphisms (RFLPs) indicated that she was not a carrier. She gave birth to a predicted non-affected male, who inherited the gene in question. In Family 2 the proposita, an obligate carrier, was initially evaluated by RFLP analysis. Two pregnancies were monitored by first trimester chorionic villous sampling. Re-evaluation indicated that all affected individuals, including one of the embryos, carried a deletion of the dystrophin gene. The identification of an RFLP within the region containing the deletion allowed unambiguous determination of the carrier status of all individuals.

Maternal cell contamination in chorionic villus samples assessed by direct preparations and three different culture methods

Presumptive maternal cell contamination (MCC) was monitored in identified male cases during cytogenetic comparison of direct techniques and three different culture regimens from 140 thoroughly dissected chorionic villus samples. Of the 66 identified male cases, 11 (16.7 per cent) showed MCC, the mean number of cells examined per case being 8.2 (direct) and 14.5 (cultures); in the direct preparations only one of a total of 457 cells examined was female, while preparations from cultures revealed MCC in 11 cases. Four of these had MCC in more than one culture regime and four had only a single female cell. The results showed that (1) dependence on the culture system alone would have given a diagnosis based on maternal cells in one (1.5 per cent) male case, thus underlining the danger of this approach (a similar undetected rate of misdiagnosis being expected in the female cases) and (2) MCC was significantly lower in cultures grown in Chang medium as compared with the other two regimes, McCoy's 5A + 15 per cent fetal calf serum and 1 per cent Ultroser G, and McCoy's 5A + 25 per cent fetal calf serum, the latter expressing the highest level of MCC.

Transabdominal chorionic villus sampling: analysis of 350 consecutive cases

We report a series of 350 patients submitted to transabdominal chorionic villus sampling (CVS). A technique using two ultrasound-guided needles and a suction pump was used. In most cases, the procedure was performed between 9 and 13 weeks. Twenty-one pregnancies were selectively terminated; nine spontaneous abortions followed the procedure and one fetal loss after 28 weeks was recorded; 153 pregnancies are in progress and 169 delivered fetuses are alive and well. Transabdominal biopsy is a feasible and effective technique for CVS.

Prenatal diagnosis of beta-thalassaemia by second-trimester chorionic villus sampling

In this study we evaluated the feasibility of second-trimester transabdominal chorionic villus sampling for prenatal diagnosis of beta-thalassaemia in 80 pregnancies at risk presenting in the second trimester at the Antenatal Service. Sampling was carried out from 13 to 20 weeks and was successful in all cases. The amount of chorionic villi obtained varied from 10 to 40 mg, which was sufficient to make fetal diagnosis by oligonucleotide analysis within 10 days from sampling in all cases. No fetal losses occurred. From these results we conclude that transabdominal chorionic villus sampling is a useful procedure for prenatal diagnosis of beta-thalassaemia in those couples presenting after the first trimester.

In vitro characteristics of human fetal cells obtained from chorionic villus sampling and amniocentesis

In vitro characteristics of human fetal cells have been investigated after chorionic villus sampling at the first trimester and amniocentesis at the second trimester of pregnancy. Light microscopy revealed heterogeneous morphology of cell types in both the chorionic villus culture and the amniotic fluid cultures. Based on the experiments performed, chorionic villus cells are more sensitive to pronase, trypsin, and versene during subculture and have a higher DNA content per single cell and release more [125I]-Beta-human chorionic gonadotropin into culture medium than those found in amniotic fluid cells. The practical applications of this study are discussed.

Trisomy 14 mosaicism leading to cytogenetic discrepancies in chorionic villi sampled at different times

Short- and long-term cultures of chorionic villi obtained in the 11th week of pregnancy revealed trisomy 14. After induced abortion trisomy 14 mosaicism was established in fetal skin and umbilical cord tissue while a second long-term culture of chorionic villi exhibited a normal karyotype. The results of the pathological investigations are discussed with respect to the cytogenetic findings.

An embryogenic model to explain cytogenetic inconsistencies observed in chorionic villus versus fetal tissue

While the fetus and placenta have a common ancestry, chorionic villus tissue does not always reflect fetal genotype. Data are presented from 15 CVS subjects in whom cytogenetic inconsistencies were observed when comparing (1) cultured chorionic villi, (2) direct chromosome preparations of intact villi, and (3) cultured fetal tissue. Embryogenic models are presented to explain these discrepancies. Mosaicism confined to direct chromosome preparations was the most commonly observed inconsistency. This can be explained by postzygotic non-disjunction limited to cytotrophoblast. In all but one instance, the abnormal cell line was limited to the placenta, with the normal cell line reflecting fetal genotype. Analysis of direct chromosome preparations from multiple individually processed villus fragments may be helpful in recognizing mosaicism confined to the placenta. While both direct chromosome preparations and villus cultures can be misleading, the latter are more likely to reflect fetal genetic status since they are derived from the extraembryonic mesoderm.

Prenatal cytogenetic diagnosis after transabdominal chorionic villus sampling in the first trimester

First trimester prenatal cytogenetic diagnosis was attempted in 350 pregnancies after transabdominal chorionic villus sampling. The cytogenetic investigation was performed using both a short-term method (24 h incubation) and cell culture. Adequate samples were obtained in 99.1 per cent and in all these cases the fetal karyotype was established. A chromosome abnormality was found in 2.0 per cent of cases. A discrepancy between the karyotype obtained after 24 h incubation and the karyotype in cell culture was observed in 2.3 per cent. Maternal cell contamination in the cultures was confirmed in 13 of 181 cases where the 24 h incubation revealed a male karyotype. Studies of culture morphology showed that colonies of convoluted cells may serve as a marker for contamination with maternal cells in culture. For the present, we recommend using a short-term method as well as cell culture for cytogenetic investigation until the problems with karyotype discrepancy and maternal cell contamination have been further clarified.

Transabdominal chorionic villus sampling for fetal genetic diagnosis. Technical and obstetrical evaluation of 100 cases

First trimester fetal diagnosis was established in 100 pregnancies at risk by transabdominal chorionic villus sampling (TA-CVS). Forty-eight per cent of the women were 35 years or more at the time of sampling. Using the double needle technique, both the aspiration and the diagnostic success rate were 100 per cent. The mean amount of villi aspirated was 28.2 mg (10-50 mg). The mean needle time was 3 min. Vaginal spotting appeared in 2 per cent of the women. Four women had therapeutic abortion due to abnormal findings and one for social reasons. Three fetuses with normal karyotypes were lost. Excluding the therapeutic abortions, the fetal loss rate was 3.2 per cent. The fetal loss rate in the amniocentesis control group (n = 200) was 3.6 per cent. The cytogenetic diagnosis was carried out by the direct preparation technique as well as by chorion villus cultivation. All karyotypes were confirmed by lymphocyte cultures from umbilical cord blood or heel blood from the newborn or from aborted fetal tissue. Transabdominal CVS is deemed a safe and easy tool for achieving chorionic villi in the first trimester.

Partial deletion of 4p in fetal cells not present in chorionic villi

A case of a prenatal diagnosis at the second trimester is presented showing a normal karyotype in 12 metaphases from chorionic villi. In all cultured amniotic cells, however, and also in all fetal fibroblasts analyzed after abortion a structural anomaly (46,XY;del 4(pter----p15.2) was detected. Prenatal diagnosis was performed because of intrauterine growth retardation, cleft lip and esophagus atresia by ultrasound. The fetal stigmata are compatible with the Wolf Hirschhorn syndrome. We conclude that amniocentesis may be indicated notwithstanding a normal CV-diagnosis in those rare pregnancies with a characteristically abnormal ultrasound.

Clinic experience of prenatal diagnosis of cystic fibrosis by use of linked DNA probes

96 families at risk of having a child with cystic fibrosis have been counselled about prenatal diagnosis by the use of linked DNA probes. Of the first 30 pregnancies 9 children have been born and confirmed to be free from CF, as predicted; 8 pregnancies were terminated (1 of these was found to be miscarrying at time of termination); 12 pregnancies, in which the fetuses are predicted to be unaffected, are in progress; and 1 has miscarried. No couple with a prenatal prediction of CF decided to continue with the pregnancy. 1 pregnancy was terminated because of a 50:50 chance of an affected fetus. In 1 twin pregnancy the affected fetus was selectively aborted, and the other baby was confirmed after birth to be unaffected, as predicted. In the other twin pregnancy the two chorionic plates could not be samples separately; the pregnancy was continued on the basis of normal findings for the lower plate, and both twins have turned out to be normal. Many couples at risk see early prenatal diagnosis as a way to help them have an unaffected child.

Chromosome mosaicism and maternal cell contamination in chorionic villi

While chorionic villus sampling allows both early and rapid prenatal diagnosis of chromosome disorders, the accuracy of this technique has not been fully established. Maternal cell contamination and pseudomosaicism represent two major sources of diagnostic error. Combined use of both direct chromosome preparations and villus cultures is important in overcoming these problems. Direct preparations of villus tissue allow recognition of maternal cell contamination of villus cultures. Conversely, villus cultures yield higher resolution chromosomes and may be helpful in differentiating between true versus pseudomosaicism when two or more cell lines are identified in direct chromosome preparations. Preliminary data suggest that analysis of direct preparations from multiple individually processed villus fragments may also be of value in this regard. Until more experience is gained, mid-trimester amniocentesis should be offered to CVS patients when mosaicism is encountered.

Techniques of chorion villus sampling

Whilst randomized studies into the safety of chorionic villus sampling (CVS) are already under way the technique is now offered as an acceptable alternative to amniocentesis in many diagnostic centres. In counselling, the obstetrician can now quote a risk to the pregnancy of 2-4% which, even if the inevitable losses before 16 weeks are excluded, represents probably at least twice the risk of amniocentesis. The evolution of the obstetric procedures has meant that the transcervical approach to CVS has been the most popular to date but there is now increasing interest in transabdominal aspiration as it minimizes the possibility of infection. The two best known transcervical methods are aspiration with a plastic or metal cannula and biopsy with rigid forceps. The majority of aspirations have been performed using the Portex cannula technique. Using this, three centres (Milan, Chicago and Philadelphia) have had experience of over 5000 cases with a failure rate of less than 1% and a minimal fetal loss of 2.2%. However, the proportion of fetal losses may be between 4 and 7% by the time complete obstetric follow-up is available (Brambati et al, 1985). A similar technique has been used with a variety of cannulae. The experience of the first 1000 cases from San Francisco (Hogge et al, 1986) led them to conclude that CVS by this technique was acceptably safe but that continuing investigation was needed before CVS was offered routinely as an alternative to amniocentesis. The only other transcervical technique that is practical for routine use is biopsy with rigid forceps. The failure and fetal loss rates associated with this method are comparable to the aspiration technique. The pioneering work of Hahnemann and his colleague Smidt-Jensen has established transabdominal aspiration as a reliable alternative approach. Its main advantage should be to minimize the risk of infection which is inherent in all transcervical techniques. In addition, it does not need to be confined to 9-11 weeks gestation and thus offers couples the possibility of diagnosis between 12 and 14 weeks rather than waiting for amniocentesis at 16 weeks. The quality and quantity of the sample depends on the size of the needle used and the technique is said to have high patient acceptability. Nevertheless, fetal losses occur following the procedure (1.8-3.2%) and it may not always be successful (failure rate 1.9-4.2%).

Risks of chorion villus sampling

From the experience accumulated in less than 4 years of chorionic villus sampling activity, much has been learned about the advantages of prenatal diagnosis in the first trimester. The safety of the procedure during this developmental stage has been extremely good. The record in this centre with over 2700 cases sampled and over 2000 deliveries has demonstrated a fetal loss rate similar to that observed in amniocentesis studies. It appears that fetal loss that may be attributed to the procedure is not more than 1% and may be less. Some of that loss appears to be correlated with avoidable trauma to the chorionic membrane area. If this conclusion is valid, then avoidance of this pattern even in the occasional difficult case may further improve the already acceptable safety record of the procedure.

A case of first trimester chromosomal mosaicism confined to the cultivation of the gestational products

The advantages of the emergence and development of chorionic villi sampling (CVS) for early prenatal diagnosis are evident, but there are a host of new diagnostic problems caused by the use of extraembryonic tissues. We report a case in which 45X/46XY mosaicism was diagnosed by cultivation of chorionic villi and fetal cells. Direct chromosomal preparations of chorionic villi failed to diagnose the abnormality.

The immediate effects of chorionic villus sampling on fetal movements

The immediate effects of chorionic villus sampling on the fetus was studied by real-time ultrasound observation of fetal movements. Thirty-minute recordings, directly before and after chorionic villus sampling, were made in 10 women. No changes were observed in the incidence or distribution of the four movement patterns studied. This held true even in the two cases that ended in a spontaneous abortion. It is concluded that chorionic villus sampling does not stimulate movements or alter the intrauterine situation in such a way that fetal movements decrease.

Karyotypic differences between cells from placenta and other fetal tissues

Six cases are reported with discrepancies between the karyotypes of placental cells and cells from other fetal tissue. The respective findings were: 48, + 7, + 18 resp. 47, + 18. 46,i(18q) resp. 46,del18(p11). 46,XX resp. 46,XX/47,XXX. 46,X,Yq+ and 46,XY resp. 46,XY. 46/47, + 12 resp. 46. 46/47, + 5 resp. 46. These differences were found in both early and term pregnancies. Care should be taken in deducing the fetal karyotype from the chromosomal pattern of placental cells.

Maternal cell contamination in cultured chorionic villi: comparison of chromosome Q-polymorphisms derived from villi, fetal skin, and maternal lymphocytes

Maternal cell contamination of chorionic villi (CV) samples used for first trimester prenatal diagnosis can cause obvious and/or unrecognized diagnostic dilemmas. The purpose of this investigation is to assess the frequency of maternal cell contamination (MCC) in chorionic villus samples and to evaluate selected parameters which might predict where contamination is more likely to have occurred. Maternal lymphocytes, chorionic villi from ultrasonically directed transcervical catheter aspiration, and fetal tissue were obtained at 8-11 weeks gestation from 45 patients undergoing elective termination. Quinacrine (Q) banded metaphases were compared from duplicate direct preparations of chorionic villi; cultured chorionic villi, fetal fibroblast tissue cultures, and maternal lymphocyte cultures. Q-polymorphisms in metaphase chromosomes were 100 per cent concordant between fetal tissue and direct CV preparation. However, evidence for maternal cell contamination occurred in 13.1 per cent of cultured chorionic villi preparations where polymorphisms were found to be identical between maternal and cultured CV and both distinct from fetal tissue preparations. Where MCC was identified, it was noted that CV cell cultivation interval was prolonged (24.2 +/- 6.8 days) compared with non-contaminated cultures (14.1 +/- 4.4 days) (p less than 0.05). We conclude that maternal cell contamination is a significant problem with chorionic villus sampling. Where direct preparations are not employed or when cultures are 'slow growing', MCC may be a significant and unrecognized complication re: fetal diagnosis. Direct preparations, multiple cultures, quinacrine banding, and maternal Q-polymorphism comparisons can minimize diagnostic dilemmas secondary to maternal cell contamination.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlamydia trachomatis infection among patients undergoing chorionic villus sampling

Chlamydia trachomatis was recovered from the cervices of 0.5% (3/560) of women undergoing chorionic villus sampling. Because this population has been identified as a low-risk group, routine screening of sexually transmitted Chlamydia prior to chorionic villus sampling is not warranted.

Chorionic villus sampling by rigid forceps: experience with 300 cases at risk for thalassemia major

In this article we report the results of chorionic villus sampling by a biopsy forceps inserted via the cervix under ultrasonic guidance in 300 pregnancies at risk for thalassemia major. A sufficient amount of chorionic villi for deoxyribonucleic acid analysis by oligonucleotide hybridization was obtained in all cases tested but one, with a success rate of 99.7%. The percentage of fetal loss, expressed as proportion of continuing pregnancies, was 4.8%. To verify the results, we carried out amniocyte deoxyribonucleic acid analysis in all the continuing pregnancies for the first 100 cases and in those in which trophoblast deoxyribonucleic acid analysis showed the heterozygous state for beta-thalassemia for the second 200 cases. At the beginning we had two cases of decidual contamination in such an amount to cause misdiagnosis. Successively more careful elimination of decidual tissue from villi avoided avoided this pitfall. These results indicate that chorionic villus sampling by a rigid forceps is a reliable and relatively safe method for fetal diagnosis of genetic diseases by deoxyribonucleic acid analysis.

Chorionic villus sampling: an analysis of the obstetric experience of 1,000 cases

Chorionic villus sampling was performed between 7 and 12 weeks gestation in 1,000 patients, 935 of whom intended to continue after fetal diagnosis. Transcervical and Transabdominal aspiration techniques were used providing a sampling success rate of 99 per cent. Anatomical and clinical contraindications to transcervical aspiration were pointed out, and the complementary role of the transabdominal approach evaluated. In the 615 concluded pregnancies an overall abortion rate of 4.1 per cent was observed. A significant association between fetal loss and number of catheter insertions was demonstrated. Bacterial inoculation by catheter insertion and colonization of uterine cavity was suspected as the cause of chorionamnionitis diagnosed in two cases (0.2 per cent) after CVS. Bleeding was the most frequent early complication (12.0 per cent) following chorionic aspiration, but was not significantly related to pregnancy wastage. Late complications, i.e. premature rupture of membranes (0.8 per cent), preterm delivery (6.3 per cent), perinatal losses (1.2 per cent), placental disorders (1.6 per cent), and congenital defects (2.6 per cent) did not exceed the expected values. Normal intrauterine growth patterns were ultrasonically estimated by cross-sectional and longitudinal studies, while the weight at birth was normally distributed in the range of the general population.

Morquio disease presenting as hydrops fetalis and enzyme analysis of chorionic villus tissue in a subsequent pregnancy

We describe the prenatal diagnosis of a fetus at risk for mucopolysaccharidosis (MPS) Type IVA (Morquio syndrome) using enzyme analysis of chorionic villus tissue. The family had two previous affected children, one with progressive nonimmune hydrops fetalis presenting at 16 weeks gestation and one mildly affected 5 year old. The parents had decreased levels of N-acetyl galactosamine-6-sulphate sulphatase in cultured skin fibroblasts indicating that carrier detection is possible for Morquio A syndrome.