Cytogenetic findings in 4952 prenatal diagnoses. An Italian collaborative study

Effects of amniocentesis for genetic purposes on the pregnancy and its outcome

An attempt was made to follow to completion the pregnancies of 2049 women who had amniocentesis for genetic purposes in a single hospital region in northern England. The object of the study was to establish the extent to which complications of pregnancy and fetal problems are attributable to the procedure. Follow-up was complete in 1750 women. Risks to the mother, other than minor abdominal discomfort following the amniocentesis, were minimal. The increase in complications to the pregnancy and delivery, the occurrence of congenital anomalies, spontaneous abortion, and perinatal death, that can be attributed to the procedure of anmiocentesis fall at the lower end of the range previously reported.

Cost-effectiveness ratio of chorionic villi biopsy for the prenatal diagnosis of chromosomal aberrations as compared with amniocentesis

The observed cost of amniocentesis for the prenatal diagnosis of chromosomal aberrations in pregnancies at risk because of advanced maternal age was compared with the estimated cost of chorionic villi biopsy (CVB). The cost of CVB was estimated to be 22% less than that of amniocentesis when the cost of the sampling procedure, the laboratory charges and the cost of spontaneous and therapeutic abortions were considered.

A survey of diagnostic amniocenteses in Oxford from 1974-1981

A survey was conducted of the results of mid-trimester diagnostic amniocenteses in the Oxford Region from 1974 to 1981. The survey used data relating to all 4357 singleton pregnancies in which an amniocentesis was performed during this period. Follow-up information on outcome was obtained in respect of 4284 (98 per cent) pregnancies. A cell culture to determine karyotype and an alpha-fetoprotein determination was carried out in all cases. From 1974 to 1981 amniocenteses became increasingly common, rising from 2 to 32 per 1000 births. The most common indication for amniocentesis was a high risk of a chromosome abnormality--56 per cent of all amniocenteses. Within this group advanced maternal age was responsible for 89 per cent of the cases. The next most common indication was a high risk of a neural tube defect (37 per cent of all amniocenteses) --in 1974 a raised maternal serum alpha-fetoprotein level accounted for only 4 per cent of these; by 1981 this had risen to 67 per cent. There were seven false-positive and 132 true-positive diagnoses of neural tube defect; since 1981, with the introduction of amniotic fluid acetylocholinesterase determination as a secondary diagnostic test for neural tube defects, there have been no further false-positive diagnoses. In 1981 76 per cent of women aged 35 years or more did not have an amniocentesis. It is not known to what extent this was due to not offering women in this age group amniocentesis or to women not accepting such an offer.

The centralized prenatal genetics screening program of New York City III: The first 7,000 cases

The Prenatal Diagnosis Laboratory of New York City (PDL) is a regional program for the prevention of genetic diseases. The administrative aspects of the establishment of the laboratory were described in papers I [Hsu, 1981] and II [Hsu and Benn, 1981] in this series. We now report our experience of the first 7,000 referrals to the laboratory. The laboratory achieved a success rate of 99.5% in obtaining a diagnosis. The frequency with which a repeat amniocentesis was required was 1.9%, usually attributable to inadequate initial amniotic fluid volume or condition. Cases were completed in an average time of 20.82 days. A total of 149 (2.13%) cytogenetic abnormalities were detected. There were 59 nonmosaic autosomal trisomies and 29 sex chromosome abnormalities. The incidence of unbalanced structural abnormalities (0.186%) was much higher than that reported in surveys of newborn infants largely because of the prenatal detection of cases with supernumerary chromosomes. The incidence of balanced structural abnormalities was also considerably higher than that found in surveys of the newborn population, in part because of the detection of subtle familial pericentric inversions of common chromosome regions (inv(Y)(p11q11), inv(2) (p11q13), and inv(1)(p11q13)). The incidence of cases with multiple independent chromosome abnormalities was no higher than expected by chance. A high incidence of mosaicism, pseudomosaicism, and maternal cell contamination was found. Screening for neural tube defects accounted for the detection of a further 16 abnormalities. Nearly all women with severely abnormal fetuses (trisomy 13, 18, 21) elected to terminate their pregnancy whereas only 62% of patients with a prenatally diagnosed sex chromosome abnormality elected to terminate their pregnancies. Full details of follow-up and confirmatory studies for unusual diagnoses are reported. Utilization of prenatal diagnosis in the New York City area has increased sharply since PDL became operational. The laboratory's success illustrates the role of a prenatal diagnosis laboratory that provides a service independent of the patient's financial status. The experience further shows the high degree of acceptance of prenatal diagnosis by individuals at high risk for a child with a genetic disorder.

Chromosome 15 anomalies and the Prader-Willi syndrome: cytogenetic analysis

The behaviour of chromosome 15 is very different from that of the other acrocentric chromosomes. The cytogenetic characteristics of rearrangements associated with Prader-Willi syndrome (PWS) are analyzed as similar rearrangements irrespective of the associated phenotype (reciprocal translocations of chromosome 15, small bisatellited additional chromosomes, Robertsonian translocations, interstitial deletions, pericentric inversions). This study suggests that: (1) The proximal ( 15q ) region and PWS seem to be indissociable ; (2) chromosome 15 has an indisputable cytogenetic originality which could be related to its histochemical properties. Chromosome 15 constitutive heterochromatin usually contains much 5-methylcytosine-rich DNA and a large amount of each of the four satellite DNAs. Furthermore the existence in the proximal ( 15q ) region of one or several palindromic sequences could be postulated to explain the great lability of this region of chromosome 15.

Prenatal diagnosis and outcome of pregnancy in 2036 women investigated by amniocentesis

The report presents the indications for prenatal diagnosis, the results from amniocentesis and details of outcome of pregnancy in 2036 women. Aneuploidy was found in 26 fetuses (1.3%) including 16 with trisomy 21 and 9 sex chromosome abnormalities. There were 38 balanced chromosomal rearrangements (1.9%): 23 of these (1.1%) were pericentric inversions of a number 9 chromosome. Only two of the chromosomal abnormalities were found in other than those mothers referred for maternal age of 35 or over. Concern is expressed at the low referral rate for older mothers in the population served (only 25% of those over 40 years). Failure of amniotic cell culture occurred in 2.8% of cultures. Maternal cell contamination was detected in 23 cultures (1.1%) with four errors in reported fetal sex. Total error estimate was 0.5%. There were 20 in vitro artefacts (1.0%) with no reporting errors. Neural tube defects were identified in 28 fetuses and there were three false-positive and one false-negative results. Data on outcome of pregnancy was available from 1805 pregnancies (96.5%): 1295 were normal (71.7%) and 510 (28.3%) showed some abnormality. Pregnancy was terminated for fetal abnormality in 53 cases (2.9%) and fetal loss occurred in 65 (3.7%). Methods, quality control, safety and service considerations are discussed. It is suggested that amniocentesis should be restricted to centres where the greatest expertise is available. The service should be improved to meet the needs of a greater number of patients. The series is compared with other studies of over 1500 cases.