Prenatal diagnosis of alpha-1-antitrypsin deficiency by PCR of linked polymorphisms: A study of 17 cases

We describe our experiences of prenatal diagnosis of alpha-1-antitrypsin deficiency using closely linked polymorphisms detected by Southern blotting and the polymerase chain reaction. Prenatal diagnosis was carried out for 17 pregnancies from 15 couples.     

Use of the chemical cleavage of mismatch method for prenatal deficiency diagnosis of alpha-1-antitrypsin

The most common mutation in alpha-1-antitrypsin deficiency, conversion of a G to an A at base 9989 (PI-Z), was detected with the chemical cleavage of mismatch method, demonstrating the power of the method for prenatal diagnosis. Exon V of the gene was amplified using the polymerase chain reaction and heteroduplexes were formed to test for the presence of the mutation. The predicted C mismatch was readily detectable with hydroxylamine, and by making the probe from the chorionic villus sample it was possible to determine that the fetus was heterozygous, not homozygous, for the mutation.     

Fetal cystic hygromata: Insights gained from fetal blood sampling

Twelve second-trimester fetuses with cystic hygroma underwent fetal blood sampling for rapid karyotyping, haematologic evaluation, and blood gas analysis. An abnormal karyotype was found in seven cases: monosomy X in five, trisomy 21 in one, and trisomy 13 in the other. Eight often fetuses undergoing blood gas analysis showed hypoxaemia, five of which were growth-retarded. Nine pregnancies were terminated. Of the remaining three, only one fetus survived the perinatal period.     

Prenatal diagnosis of thalassemia major by fetal blood analysis: Experience with 1000 cases

In this report we have summarized our experience with the prenatal diagnosis of β-thalassemia in 1000 pregnancies followed at least until 12 months after birth. In the majority of these cases, the thalassemia lesion was the nonsense mutation at the codon corresponding to amino acid 39, which produces the hematological phenotype of β-thalassemia. Fetal blood sampling was carried out by placental aspiration, by which a sufficient amount of fetal blood for analysis was obtained in the majority of cases (99 per cent). The fetal mortality associated with fetal blood sampling was 6·3 per cent. Those placental samples contaminated by maternal cells were successfully purified by Ørskov lysis. Fetal blood was analysed by globin chain synthesis on CM–52 columns, which gave reliable results. Two misdiagnoses (0·2 per cent) have been made of which one was due to a non-globin protein co-migrating with the β-chains while the other resulted from a misclassification of the type of thalassemia segregating in the family.     

Prenatal diagnosis of hemoglobinopathies in twin pregnancies by double simultaneous fetoscopy

A new technique for sampling fetal blood in twin pregnancies using two fetoscopes simultaneously is described. Two fetoscopes were inserted, one after the other, into both amniotic cavities and fetal blood samples were obtained from either the chorionic plate vessels or the umbilical cord insertion area. The observation of the bright tip of the second fetoscope behind the septum using the first fetoscope assured the successful entry of the two fetoscopes into the two different amniotic sacs. This technique was performed on 15 out of 17 patients. In all patients the fetuses were at risk of β-thalassemia major. Sampling was successful in all cases. Double simultaneous fetoscopy seems to be a safe and accurate technique without technical problems or complications. The simultaneous use of two fetoscopes opens new possibilities in intrauterine fetal surgery and research.     

Prenatal diagnosis of Chediak-Higashi syndrome

We report the first prenatal diagnosis of an affected fetus with Chediak-Higashi syndrome (CHS). Diagnosis was accomplished via fetal blood sampling at 17 menstrual weeks and was confirmed after birth. Retrospective measurement of the largest acid phosphatase-positive lysosomes in cultured amniotic fluid cells and chorionic villus cells showed that in CHS these lysosomes are significantly larger than those in normal cells. This method may be used for prenatal diagnosis of CHS by amniocentesis and chorionic villus sampling (CVS).     

Prenatal diagnosis of X-linked mental retardation with fragile (X) using fetoscopy and fetal blood sampling

Pure fetal blood, (uncontaminated with maternal blood), was obtained from two male fetuses at risk for X-linked mental retardation with fragile(X) at Xq27–28 by direct vision fetoscopy and fetal blood sampling. Both were shown to have this fragile site on the X chromosome while nine other fetal blood samples from pregnancies at risk for other X-linked diseases, or haemoglobinopathies did not show fragile sites at Xq27–28, and a blood sample from an abortus showed only 1 fragile site in 95 mitoses. Both pregnancies were terminated, cultures established from fetal tissues, and the diagnosis confirmed in each case. The problems of demonstrating the fragile site in tissues other than fetal blood in these pregnancies (such as amniotic fluid cells or fibroblasts from fetal tissues) are discussed.     

Sampling pure fetal blood in twin pregnancies by fetoscopy using a single uterine puncture

A technique for sampling pure fetal blood in twin pregnancies using a single uterine entry with a fetoscope is described. The fetoscope was inserted into one sac and after blood had been obtained from that, twin, the fetus in the other sac was sampled by trans-septal passage of the blood-sampling needle. This was done in six out of seven patients, the first in the series having two separate insertions of the fetoscope, one into each sac. Pure fetal blood was taken from all 14 fetuses, either from the placental insertion of the umbilical cord or the umbilicus, and the volume of the samples ranged from 200 μl to 1200 μl. In six patients the fetuses were at risk of β-thalassaemia and in one of haemophilia A. Some observations are made relating zygosity to the ultrasonic and fetoscopic appearance of the septum between the sacs.     

Prenatal diagnosis of glutaryl-CoA dehydrogenase deficiency: Experience using first-trimester chorionic villus sampling

We have performed prenatal diagnosis for glutaryl-CoA dehydrogenase (GDH) deficiency in 16 pregnancies at risk by measuring the enzyme activity in chorionic villus samples. In most cases, GDH activity was measured both in uncultured chorionic villus samples and in cultured chorionic cells. In 4 of the 16 cases, an affected fetus was predicted, while the remaining cases were found to be normal. In three of the four affected cases, GDH activity was measured in both uncultured and cultured chorionic cells and the correct diagnosis established by both measurements. In the fourth case, only cultured cells were investigated because the chorionic villus sample was too small for the direct assay. All four pregnancies predicted to be affected were interrupted and the diagnoses confirmed on the aborted material in three of the cases. In the fourth case, no material was available for investigation. Of the 12 pregnancies predicted to be unaffected, ten cases resulted in the birth of healthy unaffected babies while two pregnancies are still in progress.     

The fetal intrahepatic umbilical vein as an alternative to cord needling for prenatal diagnosis and therapy

Seventy-one fetal blood samplings (FBS) were attempted from the intrahepatic portion of the umbilical vein (IHV) at 18–34 weeks; 54 were attempted primarily and 17 secondarily after a failed attempt at the placental cord insertion. Fetal blood was obtained in 89 per cent of the cases. Intravascular transfusion (IVT) was attempted on 31 occasions and successful in 24 (77 per cent). In all cases of failed sampling or transfusion via the IHV, prenatal diagnosis and/or therapy was accomplished using alternative procedures. On only one occasion was the procedure postponed. There were no losses or neonatal morbidity attributable to the procedure. FBS from the IHV may be considered as an alternative approach to sampling the placental cord insertion. It is recommended in cases where the approach to the placental cord insertion is difficult or hazardous.     

Prenatal diagnosis of cystinosis utilizing chorionic villus sampling

The prenatal diagnosis of cystinosis is currently based on the increased amount of free-cystine present in amniotic fluid cells. Amniocyte cultures must be grown for at least 2 weeks to obtain sufficient cells for such measurements. Thus, the diagnosis cannot be made until close to 20 weeks gestational age by this method. We report a case in which chorionic villi were used for direct cystine measurement resulting in the in utero diagnosis of cystinosis at 9 weeks gestational age. The diagnosis was confirmed by the study of cultured chorionic villus cells, and of the 10-week abortus.     

Prenatal detection of trisomy 9 mosaicism

Chromosomal mosaicism in amniotic fluid cells poses a serious dilemma in prenatal diagnosis since the observation may represent: (1) pseudomosaicism—an inconsequential tissue culture artefact; or (2) true mosaicism—occurring in approximately 0.0 per cent of amniocenteses with a significant impact on pregnancy outcome. Mosaicism for trisomy 9 was observed in an amniotic fluid specimen obtained for advanced maternal age with two cell lines [46,XX (46 per cent)/47,XX, + 9 (54 per cent)] present in each of four culture flasks. Since more than 75 per cent of newborns with trisomy 9 mosaicism have complex cardiac malformations, a fetal echocardiogram was obtained at 20 weeks' gestation and interpreted as normal. A fetal blood sample (22 weeks' gestation) disclosed only a single trisomy 9 cell among the 100 metaphases analysed. However, a second fetal echocardiogram performed at the time of blood sampling suggested a non-specific cardiac anomaly. Fetal autopsy following elective pregnancy termination revealed several malformations including severe micrognathia, persistence of the left superior vena cava, and skeletal anomalies. Cytogenetic studies of cell cultures derived from several fetal tissues demonstrated trisomy 9 ranging from 12 to 24 per cent.     

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

Chorionic villus sampling (CVS) has emerged as a first trimester alternative to amniocentesis for the prenatal detection of genetic disorders. We report our experience in 600 consecutive CVS procedures to better delineate the safety, efficacy and reliability of this new method of prenatal diagnosis. Adequate samples were obtained at the initial visit in 97 per cent of the cases, and successful cultures were established in 98.7 per cent of these patients. Chromosome abnormalities were detected in 5.9 per cent of those pregnancies tested because of advanced maternal age (≥ 35 years). A discrepancy between the villus karyotype and that of the fetus was found in 2.0 per cent of cases, and most commonly consisted of mosaicism in the villus sample for a chromosomal abnormality that was not found in fetal samples. The risk of spontaneous abortion following the procedure was 6.3 per cent. We conclude that chorionic villus sampling is an acceptably safe and reliable procedure, but further investigation is needed before it can become an established technique in prenatal diagnosis.     

Prenatal ultrasound diagnosis of fetal scoliosis with termination of the pregnancy: Case report

Gross scoliosis of the fetal thoracic spine was diagnosed at 18 weeks gestation. The pregnancy was terminated and the fetus found to have webbing of the neck and an imperforate anus in addition to vertebral defects.     

Prenatal diagnosis of tuberous sclerosis: The use of fetal echocardiography

Fetal echocardiography was used to identify a cardiac rhabdomyoma in the second trimester. The combination of this finding with a maternal history of Tuberous Sclerosis allowed the patient and her family to make a more educated decision regarding termination of the pregnancy. Post mortem examination of the fetus confirmed the prenatal findings. This case report demonstrates the importance of ultrasound evaluation of the fetus at risk of recurrence of a genetic syndrome in which one or more anatomical defects might be seen.     

Prenatal diagnosis for Tay-Sachs disease using chorionic villus sampling

Prenatal diagnosis for Tay-Sachs disease was performed on 25 patients using chorionic villus sampling (CVS). Nineteen were diagnosed as normal, and six were affected. Normal villus extracts had both hexosaminidase (hex) A and B activity, as determined by Cellogel and polyacrylamide gel electrophoresis, while extracts from affected fetuses had only hex B activity. Compared to cultured amniotic fluid cells or fibroblasts, villi contained less hex A. Hex A levels in fresh villi and cultured trophoblasts were roughly comparable.     

Prenatal diagnosis of Hunter syndrome using fetal plasma

The X-linked Hunter syndrome or mucopolysaccharidosis II was diagnosed in a male fetus by demonstrating a severe deficiency of iduronate 2-sulphate sulphatase activity in fetal plasma obtained by umbilical fetal blood sampling at 23 weeks of pregnancy. The diagnosis was confirmed after termination of pregnancy.     

Prenatal diagnosis of carbamoyl-phosphate synthetase deficiency by fetal liver biopsy

In a pregnancy at risk for carbamoyl-phosphate synthetase (CPS) deficiency, prenatal diagnosis was attempted by fetal liver biopsy, performed at 18 weeks of gestation. CPS activity was absent and the diagnosis was confirmed after termination of the pregnancy. The technique employed for fetal liver biopsy is described together with an evaluation of its possible role in prenatal diagnosis.     

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

First trimester prenatal cytogenetic diagnosis was attempted in 350 pregnancies after trans-abdominal 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.