Prenatal diagnosis of sex in bovine fetuses by amniocentesis

The sex of 1, 056 bovine fetuses was diagnosed by cytogenetic analysis of amniotic cells collected surgically from cows made pregnant as a result of embryo transfer. The fetuses ranged in gestational age from 7 to 22 wk at the time of amniocentesis. Amniotic cells were cultured for 5 to 30 d to obtain a sufficient number of cells for cytogenetic analysis. The growth rate of 819 samples was examined in detail. On average, amniotic cells from pregnancies that were 7 or 8 wks old required about 13 d to reach a cell concentration sufficient for analysis, whereas those from pregnancies that were 10 wk old or more required only 10 d or less to reach that concentration. Final disposition of 325 pregnancies subjected to amniocentesis was unequivocally confirmed. Of these, the sex of 302 fetuses (93%) was determined with a male: female ratio of 51:49. The gender of 213 of 220 fetuses (96.8%) was correctly dignosed, as verified by examination of either 33 intentionally induced abortuses or of 187 live calves. Thirteen percent (29) of 216 pregnancies that were allowed to proceed to term ended in spontaneous abortion, a rate only about 5% higher than that reported to occur normally in embryo transfer pregnancies. The remaining 53 pregnancies were induced to abort, but it was not possible to recover and verify the sex of those fetuses. The capability to diagnose fetal sex in utero yielded other useful information as well. For example, the sex ratio of 1,056 fetuses during development from 7 to 15+ wk of gestation was found to be the same (51:49) as it was at calving. Finally, amniocentesis to determine prenatal sex provides time to alter the sex ratio of a calf crop. It may ultimately prove valuable as an adjunct to genetic engineering of cattle to identify presumptive transgenic calves in utero.     

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

Summary 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 twoof 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.     

Prenatal diagnosis of cystic fibrosis by microvillar enzyme assay on a sequence of 258 pregnancies

Summary Prenatal diagnosis of cystic fibrosis by microvillar enzyme assay on amniotic fluid supernatant has been carried out on 258 sequential pregnancies with a 1 in 4 recurrence risk, all with known outcome. In general the three enzymes evaluated, -glutamyltranspeptidase, aminopeptidase M and the intestinal isoenzyme of alkaline phosphatase, showed a high degree of concordance. However, there were two unusual patterns of microvillar enzyme activity; in seven cases a low -glutamyltranspeptidase activity was associated with elevated values of intestinal alkaline phosphatase, and in ten cases there were isolated low values of intestinal alkaline phosphatase. The former pattern was found to be associated with cystic fibrosis in five cases, while the latter was associated with a normal outcome in all ten cases. A retrospective analysis of enzyme values suggested that the optimal system for minimizing false positives and false negatives was to define foetal cystic fibrosis as a sample where two of the three microvillar enzymes were below a cut-off of half the median value for the gestational week. If such scoring were applied to the cases where conventional microvillar enzyme patterns were observed, the false positive rate was 2.3% and the false negative rate 4.4% between 17 and 20 weeks of gestation.     

Prenatal diagnosis in 200 pregnancies with a 1-in-4 risk of cystic fibrosis

Summary Prenatal diagnosis of cystic fibrosis was performed in 200 pregnancies with a 1-in-4 risk, and was based on significant modifications in amniotic fluid taken at 17, 18, 19 weeks of pregnancy, of six enzymatic assays: gamma-glutamyl-transpeptidase, aminopeptidase M, and alkaline phosphatase (total and isoenzymes). On the basis of normal values, normal outcome was predicted in 135 pregnancies reaching term, all the babies were normal. On the basis of significantly abnormal enzymatic values, an affected fetus was predicted in 56 pregnancies, 53 were terminated, and 3 went to term; the infants were affected. There were discrepancies in enzymatic values in nine cases, in eight cases normal outcome was predicted, six babies were normal and two were affected; in one case an affected baby was predicted, the pregnancy went to term and the baby is normal. Criteria giving evidence for cystic fibrosis in fetuses have been described: macroscopic observation of a typical meconium ileus, significant increase of albumin content in the meconium, and PAS-positive mucus-like material in some pancreatic acini. Using these criteria, diagnosis of cystic fibrosis has been confirmed in all the examined fetuses. The recurrence rate of cystic fibrosis was 22.5% in 147 diagnoses in which the index case had cystic fibrosis without a history of meconium ileus at birth, but was 47.5% when the index case had meconium ileus. The results of the study suggest that prenatal diagnosis of cystic fibrosis can be performed with an accuracy of 98%.     

Mosaic small supernumerary marker chromosome 1 at amniocentesis: Prenatal diagnosis,molecular genetic analysis and literature review

We present prenatal diagnosis and molecular cytogenetic analysis of mosaic small supernumerary marker chromosome 1 [sSMC(1)]. We review the literature of sSMC(1) at amniocentesis and chromosome 1p21.1-p12 duplication syndrome. We discuss the genotype–phenotype correlation of the involved genes of ALX3, RBM15, NTNG1, SLC25A24, GPSM2, TBX15 and NOTCH2 in this case.     

Prenatal enzymatic diagnosis and exclusion of Krabbe's disease (globoid-cell leukodystrophy) using chorionic villi in five risk pregnancies

Summary Galactosyl ceramide -galactosidase activity was determined in chorionic villi (CV) samples obtained between the 9th and 11th weeks of gestation from 5 women with pregnancies at risk for Krabbe's disease (globoid-cell leukodystrophy, KD). These enzyme activities were compared with those in controls, as well as with those in cultured amniotic fluid cells (AFC) from one of the five at-risk pregnancies and from 29 KD-risk pregnancies studied previously. The results of these CV enzyme analyses were such that one case of fetal KD was clearly diagnosable, one fetal genotype heterozygous for KD was presumed, and three normal fetal genotypes were suggested. The use of both uncultured and cultered CV can be recommended for prenatal KD testing, but AFC may continue to play an important role, too. Of the 58 prenatal KD tests we have evaluated since 1974, a positive diagnosis of Krabbe's disease was made (and confirmed after termination of pregnancy when feasible) in 23 which is significantly more than 25% of 58.This paper is dedicated to Professor Jürgen Peiffer (Director, Institut für Hirnforschung, University of Tübingen) on the occasion of his 65th birthday     

Prenatal diagnosis of Niemann-Pick type C disease: current strategy from an experience of 37 pregnancies at risk.

Thirty-seven pregnancies at risk for Niemann-Pick type C disease were monitored by study of cultured amniotic fluid cells (8 cases) or chorionic villus cells (29 cases) in 23 couples over the period 1984-91. An early protocol combined determination of sphingomyelinase activity with electron microscopy. The current strategy, based on the demonstration of specific abnormalities in intracellular processing of exogenous cholesterol, combines the study of the early phase (first 6 h) of LDL-induced cholesteryl ester formation and the histochemical evaluation (filipin staining after 24 h of LDL uptake) of the LDL-induced accumulation of unesterified cholesterol. Thirteen fetuses were predicted to be affected. Confirmation of the diagnosis was made by study of cholesterol processing in fetal skin fibroblast cultures and/or by demonstration of a characteristic lipid storage in fetal liver, already present at 14 w gestation. Definition of the biochemical phenotype (classical, variant, or intermediate) of the index case, with regard to cholesterol-processing abnormalities, is an absolute prerequisite to adequate genetic counseling in a given family. Prenatal diagnosis has now proved a safe procedure in the predominant (approximately 85%) group of families with the classical phenotype.     

Cytogenetical prenatal diagnosis by amniocentesis during the II and III gestation trimesters in Costa Rica

The identification of fetal abnormal chromosomes in high risk pregnancies allows proper pediatric and obstetric management of the cases as well as genetic counseling. The results of 842 genetic amniocentesis from 1986 to 1999 are reported. All procedures were performed transabdominally and under ultrasound guidance, in hospitals of the social security system and in private facilities. There were two main reasons for referral: abnormal ultrasound assessment (48% of cases) and advanced maternal age (35%). Most procedures (66%) were performed during the second trimester of pregnancy and 34% during the third trimester. Fetal cells were closed cultured and suspension harvested. Median turn around time was 14 days. In 217 amniotic fluid samples no diagnosis could be obtained, mainly due to absence of cell growth in late gestation samples or because of blood contamination. Of 625 fetal karyotypes 55 (9%) were abnormal, due to 33 trisomies (including a Robertsonian translocation trisomy 13), eight cases of monosomy X, three mosaics (including a mosaic trisomy 22), balanced and unbalanced translocations, extra structurally abnormal chromosomes and other defects. Pseudomosaicism was detected in five cases. Taking into account the reason for referral, cases studied as a result of abnormal ultrasound assessment exhibited 17% abnormal karyotypes, in contrast to 2.5% cytogenetic defects in pregnancies of women 35 years or older. Prenatal cytogenetic and sonographic findings correlated with the phenotype of the newborn in 211 cases available for follow-up. Prenatal diagnosis of fetal defects allowed genetic counseling as well as better obstetric management and pediatric care. Normal results of both tests provided reassurance to prospective parents.     

Prenatal diagnosis of chromosome abnormalities

Prenatal diagnosis of chromosome abnormalities can be performed on three different samples; chorion villi (CVS), amniotic fluid (AFS) and fetal blood (FBS). We are presenting data from our own experience on the chromosome analysis of 957 CVS, 1000 AFS and 927 FBS. A total of 69 chromosome abnormalities have been detected in the CVS, 38 in the AFS and 115 in the FBS. The type of abnormalities and their frequencies are compared between the three sampling methods. Our findings are in agreement with published data, and the higher incidence of chromosomal aberrations in the FBS group reflect the greater efficiency with which aneuploidies associated with more severe congenital malformation can be detected by ultrasound.Finally, we reported 18 cases of mosaicism in CVS, 76 in AFS and 31 in FBS. Of these cases, only 10 represented a true mosaicism of the fetus, 98 cases have been classified as pseudomosaicisms and 7 identified as maternal contamination. We have encountered 9 cases of mosaicism confined to the chorionic villi and 1 case limited to the amniotic fluid cells. There appeared to be a similarity between trisomies involved in chorion confined mosaicisms and pseudomosaicism cases of the AFS.The chromosome complement of the placenta may play an important role in the development of the pregnancy, and although a mosaic result in prenatal diagnosis could present difficulties in the prediction of the ffetal karyotype, it might give important information on the general condition of the fetus.