First trimester fetal diagnosis of genetic disorders: clinical evaluation of 250 cases

Making the most of uncertainty: Treasuring exceptions in prenatal diagnosis

Throughout the 20th century, human genetics research was driven by the identification of new variants. As pioneering geneticist William Bateson put it, novel variants were "exceptions" to "treasure". With the rise of human chromosomal analysis in the postwar period, the identification of genetic variants became increasingly significant to clinical and prenatal diagnosis. Human geneticists had long sought a broader sampling of human genetic variation, from a largely "normal" population. The expansion of prenatal diagnosis in the late 20th century offered a new resource for identifying novel genetic variants. In the prenatal diagnostic setting however, many of the exceptions to be treasured were of uncertain clinical significance, which raised anxiety among parents. In the early 1990s, providers reported that specific uncertain results from chorionic villus sampling (CVS) facilitated prenatal diagnoses that were not previously possible. Based on this, some prenatal diagnostic providers began to embrace uncertainty, when properly managed to reduce anxiety, rather than prevent it. The potential to produce uncertainty in prenatal diagnosis grew with whole genome microarray in the 2000s. Rather than outcomes to avoid, or accept as inevitable, providers presented uncertain results as starting points for research to improve the scope prenatal diagnosis, and bring future certainty.

First Trimester Noninvasive Prenatal Diagnosis: A Computational Intelligence Approach

The objective of this study is to examine the potential value of using machine learning techniques such as artificial neural network (ANN) schemes for the noninvasive estimation, at 11-13 weeks of gestation, the risk for euploidy, trisomy 21 (T21), and other chromosomal aneuploidies (O.C.A.), from suitable sonographic, biochemical markers, and other relevant data. A database(1) (1)The dataset can become available for academic purposes by communicating directly with the authors.

A 26-Year Experience in Chorionic Villus Sampling Prenatal Genetic Diagnosis

This report describes the trends of chorionic villus sampling (CVS) referred for prenatal genetic diagnosis in the past two and a half decades in a Portuguese Center. Our cohort of 491 CVS was mostly performed by the transcervical method at the 12th gestational week. Data collected within the framework of this study relate to the following: sampling method, referral reason versus abnormality and incidence of procedure-related pregnancy loss, that declined to about 0.5% over the last 15 years. The year 2000 represented a change in referral reasons for chorionic tissue collection, shifting from almost exclusively for cytogenetic testing to an increasing number of molecular tests for monogenic disorders. Herein, success rates as well as cytogenetic and/or molecular DNA results are presented. These latter include not only tests for several monogenic disorders, but also aneuploidy and maternal cell contamination screening. This retrospective analysis reiterates that CVS is a safe and reliable first trimester technique for prenatal diagnosis in high genetic risk pregnancies.

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 for fetal Rh typing: clinical implications

OBJECTIVE

The prenatal Rh typing of red blood cells obtained by chorionic villus sampling was performed with an immune rosette technique.

STUDY DESIGN

Ten Rh-negative pregnant women undergoing chorionic villus sampling at 9 to 11 weeks' gestation were studied at a large referral hospital.

RESULTS

Accurate Rh phenotyping may be done on red blood cells obtained from chorionic villi weighing 2 to 8 mg. The preparations were shown to be greater than 90% fetal in origin as demonstrated by radial immunodiffusion quantitation of fetal hemoglobin-containing cells. Of the 10 fetuses typed in the first trimester nine of the pregnancies were carried to term. In all cases typing of red blood cells confirmed the antenatal fetal red cell typing.

CONCLUSIONS

This study shows that antenatal Rh phenotyping may be performed as early as 9 to 11 weeks' gestation. This technique may be used in the management of pregnancies complicated by Rh incompatibility.

A pitfall in the prenatal diagnosis of Lesch-Nyhan syndrome by chorionic villus sampling

The ratio of the activities of catabolic enzymes such as 5'-nucleotidase and purine nucleoside phosphorylase to that of hypoxanthine-guanine phosphoribosyltransferase (HPRT) may be much higher in frozen or cultured chorionic villus cells than in cultured amniotic fluid cells, cultured fibroblasts, or red blood cells. Consequently, unless these catabolic activities are controlled the observed activity of HPRT may be greatly decreased, and a false diagnosis of Lesch-Nyhan syndrome may result. For a reliable diagnosis, the reaction products of HPRT must be protected from catabolism.

Integration of the transabdominal technique into an ongoing chorionic villus sampling program

Data are presented on 869 patients undergoing chorionic villus sampling procedures by one of two sampling techniques: 544 by a transcervical catheter aspiration method and 325 by a transabdominal two-needle aspiration method. The transcervical approach was the only procedure used in the first 330 cases, at which time the transabdominal technique was incorporated into our program. After an initial learning curve in the first 100 procedures the transcervical fetal loss rate stabilized at 2.7%, the number of patients requiring more than one catheter insertion decreased to 11%, and tissue weights greater than or equal to 10 mg were obtained in 88% of cases. The fetal loss rate for transabdominal chorionic villus sampling was 2.6%, indicating the addition of this new method did not significantly alter the fetal loss rate. Transabdominal chorionic villus sampling had an overall success rate of 99%, with only one insertion of the guide needle required for 98% of patients. Tissue weights of greater than or equal to 10 mg were obtained in 99% of cases. These results demonstrate that the transabdominal procedure can be rapidly and effectively incorporated by an operator already experienced with transcervical chorionic villus sampling. Since several contraindications exist for either chorionic villus sampling method, the availability of both techniques at a single center greatly enhances the ability to offer first-trimester fetal diagnosis to a majority of patients.

Chorionic villus sampling (CVS). Randomized study of efficacy of two transcervical biopsy methods: aspiration canulas and small forceps

A randomized study of two transcervical biopsy methods was performed. One method involved the use of an aspiration catheter and the other a tissue biopsy forceps. 120 chorionic villus samplings were performed in 30 patients. The percentage of success in taking biopsies and the resulting number of karyotypes were identical in both groups. The amount of removed trophoblastic tissue was greater when the forceps was employed. When the aspiration catheter was used, a sufficient amount of trophoblastic tissue was obtained for karyotyping purposes. It was easier to insert the aspiration catheter than the forceps. The echogenicity of the catheter and forceps were identical. The aspiration catheter has two advantages. Firstly, it is malleable and fits to the anatomy of the cervical canal and the site from which the biopsy is to be taken. Secondly, it is disposable.

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.

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.

Measurements of placental, decidual, and fetal proteins before and after chorionic villus sampling

Circulating placental [human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), decidual (pregnancy protein 12 (PP12), and fetal alphafetoprotein (AFP)] proteins were measured immediately before and within 1 h in 18 women undergoing diagnostic chorionic villus sampling (CVS) in the first trimester. An elevation of serum AFP levels was consistently seen, while fluctuations in excess of 10 per cent of the pre-CVS levels of SP1 and PP12 were seen in the majority of patients. Fluctuations in hCG and PAPP-A were consistently less than 10 per cent of pre-CVS values. Post-CVS changes in levels were not apparently associated with any feature of the technique, the pregnancy, or its outcome (one missed abortion). As feto-maternal haemorrhage is a common event, anti-D should be offered to rhesus-negative women undergoing CVS. In the prediction of subsequent miscarriage, only hCG and PAPP-A measurements should be considered.

Parental decision following prenatal diagnosis of fetal chromosome abnormality

In the event of prenatal diagnosis of fetal chromosome abnormality, parents must choose between continuation and termination of the pregnancy. To determine whether parents are capable of understanding differences in severity among aneuploidy syndromes, we examined the outcome chosen for all pregnancies in which a fetal chromosome disorder was diagnosed at Northwestern Memorial Hospital between January, 1977 and June, 1986. Among amniocentesis cases, 88% with autosomal aneuploidy were terminated, but only 41% with sex chromosome abnormalities and none with de novo structural rearrangements were terminated. Among a smaller group of chorionic villus sampling cases, all with abnormal results were terminated. Similar patterns of parental behavior were noted in other prenatal diagnosis units. We conclude that parents do distinguish among, and respond specifically to, fetal chromosome disorders of differing severity, at least in the second trimester of pregnancy. However, parents appear more inclined to terminate all pregnancies with chromosome abnormalities when the diagnosis has been made in the first trimester.

The yolk sac in early pregnancy failure

An attempt was made to visualize the yolk sac in 845 patients scheduled for chorionic villi sampling. The distribution of yolk sac diameters and the interpolating growth curve up to 11 weeks of development were analyzed in 239 pregnant women who were delivered of normal infants. The highest visualizing rate of the yolk sac in normal pregnancies was 97 at 7 weeks of gestation. A total of 130 miscarriages occurred before chorionic villi sampling. In these cases, the diameter of the yolk sac versus crown-rump length tended to be larger than found in normal pregnancies. The visualizing rate of the yolk sac in miscarriages after the embryo had been formed was significantly higher in those women who demonstrated fetal heart activity (82.1%) than in those who did not (54.5%). On the other hand, the yolk sac was observed in 44% of miscarriages without a visible embryo. These findings suggest different types of missed abortion. An abnormal karyotype was observed in 23 of 29 chromosomal analyses performed on aborted specimens. An abnormal karyotype was observed in all eight cases with only a yolk sac-like structure within the gestational sac.

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.

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.

Prenatal diagnosis of chromosomal abnormalities from chorionic biopsy samples: improved success rate using a modified direct method

Several methods for fetal chromosome analysis using chorionic biopsy samples were compared. A modified direct method for culturing villi was considered to be the method of choice and details are presented of 186 pregnancies tested prenatally. The success rate in obtaining a fetal karyotype with the direct method was 93 per cent. The fetal loss rate in the prenatal series was 4.3 per cent and congenital abnormalities in the babies already born did not differ from the expected incidence.

Chorionic villus sampling is associated with normal fetal growth

Seventy-eight singleton term neonates, delivered of women who were 35 years of age or older after chorionic villus sampling at 9 to 11 weeks' gestation, were compared with 1335 singleton control neonates delivered at term of mothers 35 years of age or older before the clinical application of chorionic villus sampling at our institution. No statistically significant differences were found in birth weight, crown-heel length, or ponderal index between control neonates and neonates delivered after chorionic villus sampling. The sample sizes necessary to detect a 5% difference in population means at an alpha error level of 0.05 and beta error level of 0.1 were calculated for the measured variables and achieved before analysis. This study suggests that patients undergoing chorionic villus sampling are not at increased risk for the development of decreased fetal growth or intrauterine growth retardation.

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.

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.

Rise in maternal serum alpha-fetoprotein concentration after chorionic villus sampling and the possibility of isoimmunization

Maternal serum alpha-fetoprotein concentrations were determined by radioimmunoassay in 72 patients immediately before and after chorionic villus sampling for prenatal diagnosis. Fifty percent showed a rise of greater than or equal to 5 ng/ml. Assuming such rises represent fetal blood crossing the intervillous space, in 14% of the cases greater than or equal to 60 microliters of fetal blood was transferred at the time of chorionic villus sampling. A positive correlation was found between the magnitude of rise in maternal serum alpha-fetoprotein levels and the amount of villi removed (r = 0.39, p less than 0.001). When cases were examined by number of passes, a greater rise in maternal serum alpha-fetoprotein levels was noted with multiple passes than with single passes for a given sample size. The transfer of greater than or equal to 60 microliters of fetal blood suggests that maternal sensitization to fetal antigens may occur after chorionic villus sampling. During biopsy, as small a sample of villi as necessary for diagnosis should be taken with as few catheter passes as possible.

Examination of products of conception terminated after prenatal investigation

A large number of district general hospitals have access to diagnostic ultrasonography and other methods of prenatal diagnosis, resulting in an increased supply of freshly terminated malformed fetuses to general histopathology departments, and there is now more open discussion of malformation and greater concern over fetal wastage. General pathologists are therefore under greater pressure to produce complete and detailed descriptions of a wide range of often complex anomalies. The dismissal of specimens as "multiple congenital anomalies" is becoming increasingly unacceptable to couples who wish to embark on further pregnancies and to their medical attendants. As in other fields an understanding of the methods and terminology in clinical use and a consistent diagnostic approach should help pathologists to extract sufficient information for accurate counselling.

The arylsulphatases of chorionic villi: potential problems in the first-trimester diagnosis of metachromatic leucodystrophy and Maroteaux-Lamy disease

Three pregnancies at risk for late infantile metachromatic leucodystrophy have been monitored using chorionic villus biopsies. In the first of these a false negative diagnosis was made following assay of arylsulphatase A in villi. Subsequent studies have shown that this error was probably due to interference from another sulphatase in the villi, although the possibility that maternal contamination was also partly responsible could not be excluded. For reliable prenatal diagnosis of metachromatic leucodystrophy using chorionic villi it is advisable that studies with the nitrocatechol substrate are carried out on fractionated homogenates, or that the natural substrate is used. Problems may also occur when chorionic villi are used for assay of arylsulphatase B for first trimester diagnosis of Maroteaux-Lamy disease.

Abnormal karyotype in the chorion, not confirmed in a subsequently aborted fetus

An abnormal fetal karyotype, containing a del 16(q21-qter) as an extra chromosome, was diagnosed in all 14 metaphases examined in a sample of chorionic villous biopsy material. After elective abortion a mosaicism for this cell-line together with a normal one was detected in the chorionic tissue. Fibroblast cultures from several fetal skin biopsies all revealed a normal karyotype.

Chorionic villus culture for first trimester diagnosis of chromosome defects: evaluation by two London centres

The maceration technique for the culture of chorionic villi has been applied by St Mary's Hospital and King's College Hospital, to a total of 225 villus aspirates of which 100 were from diagnostic cases. Two hundred and eighteen (96.8 per cent) of these were successfully karyotyped, and chromosome abnormalities were detected in 15 cases. Of the cases with a normal karyotype, 113 were male and 90 were female. Sixty-nine (77 per cent) of the female cultures were demonstrated to be fetal and a further two of these may be verified at delivery. The use of Chang medium was found to accelerate cell growth thereby reducing the interval between sampling and reporting to less than 2 weeks. An unlimited quantity of metaphase spreads was obtained suitable for the application of routine banding techniques, and comparable to those obtained from amniotic fluid culture. Experience with diagnostic cases reinforced our view that culture should always back up direct analysis and this is discussed with particular reference to the occurrence of mosaicism in the trophoblast.

First trimester chorionic villi sampling and direct chromosome preparations

Chorionic villi sampling was performed on 52 patients prior to elective termination of their pregnancies. Villi were obtained in 42, and direct chromosome preparations were successful in 41 of them. The use of a mixture of 0.075 M potassium chloride and 1% sodium citrate in the ratio of 2:1 for hypotonic treatment and 40% acetic acid for cell dispersal yielded chromosomes with good morphology and G-bands.

Clinical applications of gene probes in human genetic disease, malignancy, and infectious disease

Recent developments in recombinant DNA technology have made possible the production of gene probes consisting of cloned gene segments, cloned segments of DNA linked to genes, and synthetic gene fragments. Several methods have been developed by which these probes may be used for the diagnosis of human disease. This technology has been outstandingly successful for prenatal diagnosis and carrier detection in many genetic diseases. These methods have also been successfully applied to the analysis of human malignancies, by providing for the determination of cell lineage and clonality in lymphoid neoplasms. Finally, these methods have shown potential for rapid and sensitive diagnosis of some infectious diseases.

Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia

Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy.

Cytogenetic analysis of chorionic villi: a technical assessment

Eighty-five samples of chorionic villi from women undergoing prenatal diagnosis at 8 to 12 weeks' gestation were subjected to cytogenetic analysis. Samples were prepared by a direct technique that permits limited analysis within two hours and by a short-term culture technique that permits detailed structural analysis within one week. An adequate number of cell divisions for cytogenetic analysis was obtained from 96% of living fetuses. Using both the direct technique and short-term culture, satisfactory banded chromosomal preparations were made in 93% of cases. Eleven of 12 pregnancies (92%) shown by ultrasound to be dead shortly before sampling, had cytogenetic abnormalities. Further studies are needed to develop banding definition equivalent to that available on cultured amniocytes.

First trimester fetal karyotyping: one thousand diagnoses

Cytogenetic investigations for diagnostic purposes were performed on 1000 first trimester samples of chorionic villi (CVS) in two laboratories using similar techniques. Fetal karyotyping was the primary indication for CVS in 912 and maternal age was the major indication in 758 of them. The risk category "previous child/fetus with chromosome abnormality" included 74 diagnoses, while the category "chromosome abnormality in one of the parents" included 38 diagnoses. Sex determination was the primary indication for CVS in 53 pregnancies. The overall incidence of chromosomal abnormalities was 70, of which 47 were balanced and 23 unbalanced. The results are detailed for each of the risk categories and the incidence of abnormal karyotypes is given for each year of maternal age. In the maternal age of 35-37 years the incidence of unbalanced karyotypes was 2.9% and in the years 38 onwards it was 6.6%. The incidence of unbalanced karyotypes was about 4% when the sampling was made in the weeks 9 to 12 but six abnormal karyotypes were found among 39 CVS performed at the eight week of gestation. The 11 trisomies of the type not found at birth were clustered between the 8th and the 10th week of pregnancy. The technical problems encountered in this experience and the preliminary estimates of fetal loss are discussed.

[Chorion biopsy--a new method of prenatal diagnosis]

Chorionic villi are derivates of the trophoectoderm and therefore have the same genetic constitution as the embryo. The recently developed techniques of chorionic villi sampling in the 9th to 11th week of pregnancy and the cytogenetic analysis of this material open a new field in the prenatal diagnosis of chromosomal aberrations. With this method, a result is obtained about 8 weeks earlier than with the classical procedures performed by amniocentesis. This offers major advantages to both patient and physician.

Clinical experience with 50 cases of first-trimester fetal diagnosis by chorionic biopsy

Prenatal diagnosis by chorionic biopsy was undertaken between the eighth and 12th weeks of pregnancy in 50 patients at risk of chromosomal or genetic abnormalities. Samples from 45 patients were karyotyped. A DNA analysis for the detection of homozygous beta-thalassaemia was undertaken in five patients. The sample from one patient at risk of haemophilia in the fetus was subjected to DNA analysis after a male fetus was confirmed on karyotyping. Abnormal karyotypes were detected in four fetuses while three had homozygous beta-thalassaemia.

A randomized study of three cannulas for transcervical chorionic villus sampling

A randomized trial involving 200 transcervical chorionic villus samples taken with three different cannulas was undertaken. In terms of karyotype recovery and ease of insertion the aluminum cannula performed best although the placental site influenced the ability to recover villi for all cannulas.