Amniocentesis and chorionic villus sampling.

Amniocentesis and chorionic villus sampling have been shown through prospective, multicenter trials to be safe and effective methods of prenatal diagnosis; accordingly, a knowledge of these tests is important for those physicians who care for women during their childbearing years. We review the indications, techniques, safety, accuracy, and efficacy of amniocentesis and chorionic villus sampling and compare the advantages and disadvantages of each diagnostic test. This review should enable physicians to provide appropriate counseling and information to women at increased risk for fetal abnormalities detectable by either of these procedures.     

Investigations of chorionic villi after chorionic villus sampling (CVS)

Summary This report documents the first 262 cases of chorionic villus sampling (CVS) performed in parallel with cytogenetic and morphological investigations. Histomorphological examination of these CVS specimens gave suitable results in about 96% (251 cases). Of the latter, 201 samples (80.1%) exhibited villi and 176 (70.1%), maternal tissue. Viability and maturation of the chorionic villi were determined light microscopically even in cases with few villus trees. Smooth avascular villi with poorly defined margins observed under an inverted microscope, less than 10 mitoses after short-term incubation, and reduced growth of cell cultures were significantly correlated with sampling at the chorion laeve by means of histomorphologic criteria. Villi from cases exhibiting cytogenetically proved chromosomal abnormalities were characterized by molar degeneration or stromal fibrosis, or both, in 4 out of 9 cases, including 3 mosaics. In early abortions (within 3 weeks after CVS), an unexpectedly high rate of pathohistological changes within maternal tissue was evident. These results need further confirmation by investigation of a greater number of samples with immunohistochemical and morphometric methods.     

Health-related quality-of-life assessment of prenatal diagnosis: chorionic villi sampling and amniocentesis

This study assesses the health-related quality-of-life (HRQL) effects of chorionic villi sampling (CVS) and genetic amniocentesis (GA), including both process and outcomes of prenatal diagnosis. The HRQL of 126 women participating in a randomized controlled clinical trial of CVS versus GA in Toronto and Hamilton, Ontario, was assessed in four interviews at weeks 8, 13, 18, and 22 of pregnancy. Statistical analyses included analysis of variance, repeated measures analysis of covariance, chi-square, Fisher's exact test, Student's t-tests, and paired t-tests. Utility scores for patients undergoing CVS exceeded those for GA patients at week 18 (p = 0.04). Utility scores for hypothetical health states did not differ significantly by trial arm. CVS results in slightly improved HRQL during prenatal diagnosis. This advantage needs to be weighed against the high disutility patients attach to infrequent outcomes associated with pregnancy losses, equivocal diagnoses, and diagnostic inaccuracy.     

No effect of maternal smoking in early pregnancy observed on chromosome aberrations in chorionic villus samples

The effect of maternal smoking on first trimester chorionic villus samples (CVS) was studied by analysing the frequency of chromosome aberrations (CAs) among 20 non-smoking and 20 smoking mothers. The aberrations were classified as chromosome- and chromatid-type breaks and gaps. No statistically significant differences were found in the frequencies of CAs between non-smoking mothers (5.4% or 2.0% gaps excluded) and smoking mothers (3.5% or 1.0% gaps excluded).     

Level of alpha-fetoprotein in maternal serum before and after chorionic villus sampling

To evaluate incidence and severity of feto-maternal transfusion post-chorionic villus sampling (CVS), maternal serum AFP (MSAFP) were determined for 88 patients before and 15 minutes after CVS. To know whether MSAFP elevation could have clinical implications, a questionnaire was sent to the patients researching if they have had haemorrhages, temperature, spontaneous abortion or premature delivery in the period post CVS. Results of the present study indicate that 44.7% of patients present MSAFP significative elevation (greater than or equal to 8 micrograms/l), a variable elevation (from 8 to 423 micrograms/l). There is no relation between MSAFP elevation and unfavourable events post CVS.     

Transabdominal chorionic villus biopsy in second and third trimesters of pregnancy to determine fetal karyotype.

Transabdominal chorionic villus biopsy is an established method of obtaining material for analysing fetal chromosomes in the first trimester of pregnancy but has not been widely used for karyotyping in the second and third trimesters, when rapid results are required. The technique was evaluated in two groups of patients, comprising 106 at risk of having a fetus with chromosomal anomalies (105) or X linked disease (one) studied between 13 and 22 weeks (median 15 weeks) of gestation (group 1) and 21 with abnormal fetal findings on ultrasonography studied between 13 and 38 weeks (median 27 weeks) (group 2). Chorionic tissue was collected at the first attempt in 109 patients and at the second attempt in a further 17 independent of the position of the placenta. In one case from group 1 sufficient material for analysis could not be obtained. Seven abnormal karyotypes (six in group 1 and one in group 2) were diagnosed. Karyotyping was unsuccessful in two cases in group 1 (at 17 and 18 weeks'' gestation) and in two in group 2 (at 29 and 38 weeks'' gestation). Follow up of group 1 four weeks after sampling showed no signs of adverse fetal development apart from one unexplained intrauterine fetal death. The findings suggest that chorionic sampling is a safe and valuable additional technique for the late detection of chromosomal defects.     

Ultrastructure of the chorionic villus of the human placenta of the second and third trimester pregnancy.

38 human placentae of the 14th week of normal gestation were studied ultrastructurally. The thickness of the syncytial layer of villi varied markedly, and the syncytial cytoplasm showed marked vacuolization, which increased in the course of pregnancy in association with intensification of processes of resorption and absorption and hormonal function of the syncytium. Toward the end of the 2nd and at the beginning of the 3rd trimester of pregnancy, hypertrophic cytotrophoblastic cells appeared, whose ultrastructural character indicated functional stimulation. This observation contradicts the widely held view that cytotrophoblastic cells undergo gradual reduction in the course of pregnancy.     

A meta-analysis of case-control and cohort studies with interval-censored exposure data: application to chorionic villus sampling

Chorionic villus sampling (CVS) is a valued method of prenatal diagnosis that is often preferred over amniocentesis because it can be performed earlier, but which has also raised concern over a possible association with increased risk of terminal transverse limb deficiency (TTLD). We present and apply a meta-analytic method for estimating a combined dose-response effect from a series of case-control and cohort studies in which the exposure variable is interval-censored. Assuming coarsening at random for the interval-censoring, and calling upon the familiar result of Cornfield to pool case-control and cohort information on the association between a rare binary outcome and a multilevel exposure variable, we form a likelihood-based model to assess the effect of gestational age at the time of CVS on the presence or absence of a rare birth defect. Effect estimates are computed with a variant of the EM algorithm termed the method of weights, which enables the use of standard weighted regression software. Our findings suggest that CVS exposure at early gestational age leads to an increased risk of TTLD.     

Genetic counselling, carrier detection, and prenatal diagnosis in hemophilia. A service experience

Our experience over three years (1984-1986) is described in carrier detection and prenatal testing for hemophilia. We have analysed 50 families: 37 hemophilia A and 13 hemophilia B, 22 isolated cases and 28 familial. Eighty-three women belonging to this panel asked for a genetic risk. Pedigree and coagulation studies were performed to estimate genetic risks according to the Bayesian method. At this point, 40% of the females at risk were recognized carriers before the DNA analysis. Molecular biology allowed the detection of only 7% more carriers and the exclusion of 34%. In 19% of the cases, it was impossible to estimate the genetic risk because the families were uninformative for the DNA polymorphisms used. Twenty-two prenatal diagnoses were performed; 3 affected male fetuses were recognized by DNA analysis and pregnancies were terminated. Eleven healthy boys were born.     

Protein measurements in the early prenatal diagnosis of spina bifida.

Measurement of beta-lipoprotein concentration in amniotic fluid is introduced as a new parameter for the early prenatal diagnosis of spina bifida. It was successful in 15 cases of spinal bifida, but failed in 5 cases of open spina bifida and 2 cases of closed spina bifida. All assays were performed before the end of the second trimester and most between 15 and 20 weeks of pregnancy. beta-lipoprotein was compared with alpha-fetoprotein and alpha2-macroglobulin in its effectiveness in diagnosing spina bifida at an early enough date to allow a termination of pregnancy.     

Effect of sampling on variability and plateau in oxygen uptake

To evaluate the effect of the gas exchange sampling interval on variability and plateau in O2 uptake (VO2), 10 subjects underwent steady-state treadmill exercise at 50% maximal VO2 and 6 subjects underwent maximal testing using a ramp protocol. During steady-state exercise, gas exchange data were acquired by using 10 different sampling intervals. The variability in VO2 was greater as the sampling interval shortened (SD = 4.5 ml.kg-1.min-1 for breath-by-breath vs. 0.8 ml.kg-1.min-1 for 60-s samples). The breath-by-breath data suggested a Gaussian distribution, and most of the variability was attributable to tidal volume (51%). During ramp testing, the slope of the change in VO2 (for each sample) was regressed with time. Considerable variability in the slopes was observed throughout exercise, and in each subject the slopes varied about zero, demonstrating both positive and negative values throughout submaximal effort. These observations were made despite the use of large sampling intervals. Shortening the sample resulted in even greater variability. We conclude that 1) the sampling interval can have a major impact on gas exchange data during exercise and 2) considerable variability exists in the slope of the change in VO2 with a consistent change in external work regardless of the sample used, suggesting that a plateau (defined as the slope of a VO2 sample at peak exercise that does not differ significantly from a slope of zero) in VO2 is not a reliable physiological marker for maximal effort.     

Method of sampling chorionic villi in first trimester of pregnancy under guidance of real time ultrasound.

Samples of chorionic villi were obtained in the first trimester by aspiration using a cannula passed transcervically under the guidance of real time ultrasound. In initial studies in 47 anaesthetised patients immediately before therapeutic abortion a method was developed giving a success rate of 89%. In 10 patients successful sampling was performed as an outpatient procedure without anaesthesia. In all, seven diagnostic procedures were undertaken and four of the five unaffected pregnancies continued. The technique of chorionic villous sampling using real time ultrasound is simple to learn and yields material for biochemical analysis and chromosomal study without the need for tissue culture. The exact obstetric risk, however, remains to be defined.     

Prenatal detection of chromosome aneuploidies in uncultured chorionic villus samples by FISH.

We developed a 1-d FISH assay for detection of numerical chromosome abnormalities in uncultured chorionic villus samples (CVS). Probes specific for chromosomes 13, 18, 21, X, and Y were used to determine ploidy by analysis of signal number in hybridized nuclei. Aneuploidy detection using this assay was directly compared with the results obtained by conventional cytogenetic analysis in a consecutive, clinical study of 2,709 CVS and placental samples. The FISH assay yielded discrete differences in the signal profiles between cytogenetically normal and abnormal samples. On the basis of these results, we generated FISH-assay cutoff values that discriminated between karyotypically normal and aneuploid samples. Samples with mosaicism and a single sample with possible heritable small chromosome X probe target were exceptions and showed poor agreement between FISH results and conventional cytogenetics. We conclude that the FISH assay may act as a more accurate and less labor-demanding alternative to "direct" CVS analysis.     

Thyroid-stimulatory effects of human chorionic gonadotrophin in early pregnancy. In vivo and in vitro studies

Human chorionic gonadotrophin (hCG) shares structural similarity with pituitary thyrotrophin (TSH) and may act as a thyroid stimulator. We have studied serum hCG levels, thyroid function tests and the ability of serum to stimulate cultured thyroid cells in 40 subjects between 6 and 12 weeks of pregnancy. Serum free tri-iodothyronine was increased and serum TSH reduced in pregnancy samples (both p less than 0.05). hCG was detectable in all pregnancy sera with a mean level of 105.6 X 10(3) U/l. Serum from 24 of the 40 (60%) patients stimulated iodide uptake into cultured FRTL-5 thyroid cells. The potency of sera in stimulating cells correlated with the hCG level (r = 0.710, p less than 0.01). The stimulatory activity in some, but not all, sera could be specifically neutralized with antiserum to hCG. Partially purified hCG stimulated iodide uptake and growth of thyroid cells at concentrations of 50 X 10(3) U/l and above. In these experiments, 25 X 10(3) U/l of hCG produced equivalent stimulation to 1 mU/l of TSH. In 8 patients tested before and after termination of pregnancy, the thyroid-cell-stimulatory activity of serum declined rapidly in parallel with serum hCG. hCG may stimulate the thyroid gland at concentrations which prevail in normal pregnancy. Its potential as a physiological regulator of the thyroid gland is not widely appreciated and requires further study.     

First-trimester prenatal diagnosis of mucolipidosis II (I-cell disease) by chorionic biopsy

We investigated the possibility of mucolipidosis type II (ML II) prenatal diagnosis by lysosomal enzyme determination on trophoblast biopsy obtained at 10 weeks of gestation in two pregnancies at risk. Diagnosis of ML II was made in both cases on fresh chorionic villi on the basis of depressed beta-galactosidase activity, and after abortion, the diagnosis was confirmed on fresh fetal tissues and on cells cultured from trophoblast and fetuses. We stress the importance of culturing cells from the trophoblast biopsy to ensure a reliable diagnosis.