Risk of amniocentesis and laboratory findings in a series of 1500 prenatal diagnoses

The experiences with 1500 midtrimester prenatal diagnoses are reported. Abnormal findings of amniotic fluid investigations led to 43 therapeutic abortions. In ± 30 percent of the chromosome anomalies diagnosed, the significance of the effect on fetal development was inconclusive. The outcomes of all pregnancies except one are known. Fetal loss and perinatal mortality involved 69 cases, 23 (33 percent) of which occurred within three weeks after amniocentesis. In these 23 cases there appeared to be a relationship between the degree of experience of the gynaecologist and fetal loss: 3·7 percent when this experience was limited to a maximum of 10 punctures diminishing to 0·3 percent with an experience of more than 50 punctures. It is concluded that the risk of an abortion due to amniocentesis decreases as the gynaecologist becomes more experienced with the puncture technique.     

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures is described. The technique is based upon several key steps including: (1) reduced colcemid concentration, (2) reduced exposure to trypsin-EDTA, and (3) maintaining cells in single suspension by adjusting cell concentration appropriately. Chromosomes with banding resolution up ot 800 bands per haploid set can be routinely produced. The described methodology is particularly useful in defining and establishing the clinical significance of subtle structural aberrations.     

A 10-year survey, 1980–1990, of prenatally diagnosed small supernumerary marker chromosomes,identified by fish analysis. Outcome and follow-up of 14 cases diagnosed in a series of 12 699 prenatal samples

A cytogenetic survey and follow-up studies were made of 14 cases with supernumerary marker chromosomes, identified among 12 699 prenatal samples, investigated at our institution over a 10-year period from 1980 to 1990. FISH (fluorescence in situ hybridization) techniques were employed to identify the chromosomal origin of the marker chromosomes. Five cases were familial, all derived from acrocentric chromosomes, and all without apparent phenotypic effects in the children. Nine cases represented de novo aberrations. In two cases (one with a marker from chromosome 14 or 22, the other with a ring-like marker derived from chromosome 17), the pregnancies continued and apparently normal babies were delivered at term, but the child with a marker derived from chromosome 17 showed slight psychomotor retardation at 2 years of age. All other pregnancies with de novo markers were terminated. In three cases, significant abnormalities were found at autopsy. One of these had an isochromosome 12p and the phenotype was consistent with Pallister-Killian syndrome. In conclusion, marker chromosome identification, as well as clinical follow-up, is essential for the purpose of improving genetic counselling.     

Human chromosomes in prenatal diagnosis: A one step high resolution technique

A simple high resolution technique for human chromosomes is described for fibroblasts obtained from amniotic fluid cell cultures. The application and clinical significance of this technique in prenatal diagnosis is discussed.     

A collaborative study of the segregation of inherited chromosome structural rearrangements in 1356 prenatal diagnoses

A collaborative study involving 71 European prenatal diagnosis centres has collected 1356 observations on the karyotype of fetal cells in diagnoses performed in couples in which a parent had a balanced structural rearrangement. The segregations of the inherited chromosome structural rearrangement were analysed in relation to the types of rearrangement, to the sex of the carrier parent, the methods of ascertainment of the anomaly in the family, the chromosomes involved and the potential imbalance of the anomaly. Wide differences in the incidence of unbalanced fetuses were observed in relation to these criteria, and these results can be used in counselling parents with balanced rearrange- ments. Distortions in segregation of normal versus balanced karyotypes were observed in some types of anomalies.     

Cytogenetic experience in prenatal fra(X) detection on amniotic fluid cultures

Since 1987, we have had experience with 13 prenatal diagnoses of 11 women at risk for the fragile X syndrome by cytogenetic studies on amniotic fluid cultures. The induction method included TC 199 medium and methotrexate. Results were obtained in all cases. Ten were males and three were prenatally diagnosed as being affected. Three were females and none of them was fra(X)-positive. Results were confirmed in 10/13 cases. In these cases, we had neither false-positive nor false-negative results.     

Cytogenetic analysis of chorionic villi for prenatal diagnosis: An ACC collaborative study of U.K. data

A prospective 3-year collaborative study was undertaken in 1987 to collect cytogenetic data from diagnostic chorionic villus samples (CVS) in the U.K. in order to determine the predictive value of the chromosome abnormalities encountered. Twenty-seven laboratories contributed a total number of 7595 cases, of which 97·6 per cent were successful. Excluding single cell anomalies, a total of 480 cytogenetic abnormalities were reported, of which 137 were familial structural rearrangements and 343 were de novo problems. Non-mosaic trisomies of chromosomes 13, 18, and 21 (n=157), non-mosaic sex chromosome abnormalities (n=33), and triploidy (n=6) were all confirmed in cells of fetal origin where follow-up information was available. Of the nine remaining non-mosaics including tetraploidy, trisomies of other autosomes, and extra markers, only a trisomy 16 and a case of a supernumerary marker proved genuine. Eighty-eight cases of mosaicism were reported to the study, of which only nine were confirmed as genuine: two cases involving chromosome 13, one trisomy 18, two examples of extra marker chromosomes, three 45,X, and one 47,XXX. There were no reports of false-negative findings. Presumptive maternal cell contamination was encountered in 39 cases, a detected incidence of 0·5 per cent. Four cases of presumptive ‘vanishing twin’ were recorded: in three of these, direct preparations showed a female karyotype, whereas cultures indicated a male (with male fetuses in two cases). The fourth case was of a female fetus with male and female cells in the CVS cultures. Subtle structural chromosome abnormalities were missed in three instances. Accurate prediction of the fetal karyotype was shown to require detailed knowledge of both the nature and the distribution of abnormal cells in the extra-embryonic tissues. In many cases, this could only be made where results from direct preparations and cultured cells were available. A number of conclusions were reached from these and similar data in the literature regarding the reliability of chromosome findings in CVS.     

Preparation of high resolution chromosomes from amniotic fluid cells

A relatively simple method of obtaining high resolution chromosomes from amniotic fluid cells is described. The elongated chromosomes are achieved by adding ethidium bromide (5μg/ml) to the culture 4 1/2 hours before harvesting and the high resolution banding can be produced by usual banding procedures.     

Cytogenetic analysis of 2928 CVS samples and 1075 amniocenteses from randomized studies

We report cytogenetic results from a randomized Danish chorionic villus sampling (CVS) and amniocentesis (AC) study including 2928 placental and 1075 amniotic fluid specimens processed in the same laboratory. The results are presented in groups comparing CVS with amniocentesis and transabdominal (TA) CVS with transcervical (TC) CVS as randomized. More abnormalities and more ambiguous diagnostic problems were found in placental tissues than in amniotic cells. There were no diagnostic errors and no incorrect sex predictions. Mosaicism was detected in 1 per cent of all cases of CVS (discordancies included). When confirmation studies were done, 90 per cent were found to be confined to the placenta. Eight cases (0.7 per cent) of mosaicism/pseudomosaicism were seen in amniotic fluid specimens, and two cases of five with confirmation studies were confirmed in the fetus. The rate of mosaicism/pseudomosaicism in CVS and AC specimens differed (P <0.05). The rate of pseudomosaicism in cultures of villi and amniotic fluid cells was 0.5 and 0.6 per cent, respectively. Single-cell aneuploidy was observed in 1.8 per cent of villi and 1.4 per cent of amniotic fluid cell specimens. Maternal cell contamination (MCC) was seen more often after TC sampling (4.5 per cent) compared with TA sampling (1.5 per cent), but posed no problems in interpretation. Compared with the processing of cultured specimens, the short-term method of preparation of villi in our laboratory doubled the technicians' workload. For practical and economic reasons we have ceased the routine use of short-term preparations.     

Decision making during the prenatal diagnostic procedure. A questionnaire and interview study of 211 women participating in prenatal diagnosis

Counselling in connection with prenatal diagnosis (PND) is a common task for the obstetrician and the midwife. However, the decision making processes of pregnant women are not completely known, for instance, the questions of women's autonomy, the decision on how to act in the case of an abnormal test, and the partner's participation in the decision. A questionnaire and interview study was carried out among 211 women undergoing PND by amniocentesis or chorionic villus biopsy. Most women in the sample indicated that PND was completely voluntary. However, at the same time almost every woman reported that it was difficult to decline from PND when offered. Even before the visit to register at the antenatal clinic, most of the women (83 per cent) had made up their minds to have PND. At the time of the test, many of the participants (62 per cent) had decided in favour of a legal abortion if the test indicated an abnormality in the fetus. At the same time, however, the data indicate a need for reflection and ambivalence, which the medical staff have to accept. In the questionnaire most of the women stated that they and their partners had similar attitudes towards PND, but when interviewed 38 per cent of the women admitted some differences between their own attitudes and their partners'. Although some women reported considerable deliberation and ambivalence, most of them said that they would undergo PND in another pregnancy.     

Cytogenetic prenatal diagnosis and its relative effectiveness in the mersey region and North Wales

The relative effectiveness of cytogenetic prenatal diagnosis in the Mersey Region and North Wales is presented by estimating the percentage detection rates of Down's syndrome annually following amniocentesis from 1978–1984 inclusive. Tables indicating the percentage of screened pregnancies, types of chromosomal aberrations detected and the occurrence of Down's syndrome in mothers in age groups of five-year intervals are also presented. The average prenatal detection rate for Down's syndrome (estimated at the time of birth) was 15–15 per cent over the years 1978–1984 and was above 22 per cent for the last two years when 44–13 per cent of all pregnancies to mothers of 35 years and over were investigated.     

Swedish survey on extra structurally abnormal chromosomes in 39 105 consecutive prenatal diagnoses: Prevalence and characterization by fluorescence in situ hybridization

During 7 years (1985–1992), 39 105 consecutive prenatal diagnoses (34 908 amniocenteses and 4197 chorionic villus samples) were made at the five largest clinical genetic laboratories in Sweden. Thirty-one cases of extra structurally abnormal chromosomes (ESACs) were found, giving a total prevalence of 0·8 per 1000. Twelve ESACs were inherited, 14 were de novo and in five the parental origin was unknown. This gives an estimated prevalence of 0·3–0·4 per 1000 for familial and 0·4–0·5 per 1000 for de novo ESACs. Retrospectively, the ESACs were characterized by fluorescence in situ hybridization (FISH). In nine cases, no material was available for this analysis. In 21 of the remaining 22 cases, the chromosomal origin could be identified by FISH. Seventeen of these (81 per cent) were derived from the acrocentric chromosomes, of which 13 originated from chromosome 15 (62 per cent). The most common ESAC was the inv dup(15) (57 per cent). Two cases were derived from chromosome 22, one from chromosome 14, and one from either chromosome 13 or chromosome 21. The four remaining cases consisted to two i(18p)s and two small ring chromosomes derived from chromosomes 4 and 19, respectively.     

Microculture of fetal blood for prenatal cytogenetic studies from blood-stained amniotic fluid

An alternative method to the culture of amniotic fluid cells for prenatal diagnosis of chromosome disorders is proposed. Microculture of fetal blood can be used when fetal blood is drawn at amniocentesis through accidental puncture of the placenta. An easy discrimination of fetal red cells, a good response of fetal lymphocytes to PHA and the possibility of identification of the fetal karyotype from the maternal one are the technical bases of this method. This technique offers some undoubted advantages: a reduced need for repeating amniocentesis because of a lack of growth of AF cells due to massive contamination with red cells; a result may be obtained sooner. Thirty-seven cases out of 1092 amniocenteses were processed in this way (3·4 per cent). In two cases no mitoses were obtained but in the others the diagnosis was confirmed by the results of AF cell culture and/or by the outcome of pregnancy.     

Prenatal investigation of a 45,X/46,X,r(?) karyotype in amniocytes using fluorescence in situ hybridization with an X-centromeric probe

The karyotype of cultured amniotic fluid cells obtained on the indication of advanced maternal age was shown to be a mosaic 45,X/46,X,r(?). The small size and banding pattern made it difficult to determine whether the ring was derived from and X or a Y chromosome, or even from an autosome. By using an X-centromeric probe and fluorescence in situ hybridization (FISH), we demonstrated the ring to have an X centromere. Thus, a more complete genetic counselling was possible. This confirms the usefulness of FISH in identifying and characterizing this and other chromosome rearrangements in prenatal diagnosis.     

Future use and development of prenatal diagnosis. Consumers' attitudes

The rapid progress of prenatal diagnosis and genetic tests makes it important to investigate attitudes towards this development. A total of 40 women and 20 men with personal experience of prenatal diagnosis for chromosome aberrations were interviewed about their moral opinion of the development. The majority (88 per cent) considered it certain or probable that all new methods developed will also be used in the future. The majority (62 per cent) were hesitant about testing for common disorders, e.g., diabetes mellitus and rheumatoid arthritis, but regarded it justified in some situations. One-third of the individuals (31 per cent) wanted some kind of restrictions for the use of the tests, but only 13 per cent recommended legislation for this purpose. The majority (84 per cent) believed that ethical principles are influenced by scientific progress. In most aspects, the women and their partners had similar attitudes. However, 82 per cent of the women but only 20 per cent of the men considered that the couple itself should decide about prenatal diagnosis. The results demonstrated a considerable respect regarding the difficult choices associated with the development of prenatal diagnosis, also among those who have decided in favour of the test. The study indicated a greater need for autonomy among women than among men.     

Results from a reference laboratory for prenatal diagnosis of sickle cell disorders in Cuba

A nationwide programme for the prevention of sickle cell (SS and SC) disorders was initiated in Cuba in 1983. Couples at risk were identified by screening pregnant women and the partners of those who carry an abnormal haemoglobin, followed by genetic counselling and the offer of prenatal diagnosis. Prenatal diagnosis was performed in one laboratory, which had carried out 1068 prenatal tests for Hb SS and SC disorders by the end of 1992. The centralization of the service has permitted rapid identification and resolution of problems.     

Carrier detection and prenatal diagnosis in Norrie disease

We report the use of DNA probes to determine carrier status in three young women from a large kindred with Norrie disease. One of the women requested prenatal diagnosis during pregnancy. In this pedigree, Norrie disease was not characterized by a deletion at DXS7.     

A revisit of trisomy 20 mosaicism in prenatal diagnosis—an overview of 103 cases

One hundred and three cases with prenatal diagnosis of trisomy 20 mosaicism through amniocentesis were reviewed. Approximately 90 per cent (90/101) of the cases were associated with grossly normal phenotype. It is likely that, in the majority of cases, cells with trisomy 20 were extraembryonic in origin or largely confined to the placenta. However, in some cases, the cells with trisomy 20 were confined to certain specific fetal organs or tissues such as kidney, skin, etc. Cytogenetic follow-up studies in liveborns should include a culture from urine sediment.     

Amylo-1,6-glucosidase activity in cultured cells: A deficiency in type III glycogenosis with prenatal studies

Deficiency of amylo-1,6–glucosidase activity was expressed in parallel in liver and skin fibroblasts from a patient with type III glycogenosis. In crude extracts of control liver and muscle, amylo-1, 6–glucosidase (M.W. 164000) was identified by immunoprecipitation; no cross-reacting material was found in the patient's liver. Assay of amylo-1,6–glucosidase activity in cultured skin fibroblasts from the affected family revealed less than 10 per cent of control value in mutant homozygous cells whereas in cells from the parents, activity was reduced to 40–60 per cent of the control value. Activity in cultured amniotic fluid cells was similar to that of control fibroblasts. In cultured amniotic fluid cells obtained during the mother's subsequent pregnancy, the normal amylo–1,6–glucosidase activity measured, predicted correctly the outcome of this pregnancy prior to the 20th week of gestation.