Terminal transverse limb defects and early chorionic villus sampling: evaluation of 4,300 cases with completed follow-up

Synthesis of evidence from epidemiological studies with interval-censored exposure due to grouping

We describe a method for assessing dose-response effects from a series of case-control and cohort studies in which the exposure information is interval censored. The interval censoring of the exposure variable is dealt with through the use of retrospective models in which the exposure is treated as a multinomial response and disease status as a binary covariate. Polychotomous logistic regression models are adopted in which the dose-response relationship between exposure and disease may be modeled in a discrete or continuous fashion. Partial conditioning is possible to eliminate some of the nuisance parameters. The methods are applied to the motivating study of the relationship between chorionic villus sampling and the occurrence of terminal transverse limb reduction.

Malformations reported in chorionic villus sampling exposed children: a review and analytic synthesis of the literature

PURPOSE

To determine whether the frequency of vascular disruption defects, other than limb defects, is increased in reports of chorionic villus sampling (CVS) exposed children compared with an unexposed population.

METHODS

Only studies that reported the total number of CVS-exposed pregnancies and details of pregnancy outcome, including all the malformations, were included. Twenty-five articles met these criteria.

RESULTS

The frequencies of gastroschisis, intestinal atresias, and clubfoot were significantly increased among the CVS-exposed infants as compared with the baseline unexposed population. The frequencies of other vascular disruption defects, including Poland sequence, amniotic band sequence, and cleft lip/cleft palate, were not increased.

CONCLUSION

CVS-exposed children have an increased frequency of intestinal atresia, gastroschisis, and clubfoot compared with the nonexposed population. The fact that an increased frequency of other defects attributed to vascular disruption was not found may be due to under-ascertainment, misclassification, or "lumping" of the defects identified in previous studies.

Noninvasive means of identifying fetuses with possible Down syndrome: a review

Women who are 35 years or older are offered invasive prenatal testing because of the increased risk of chromosomal abnormalities, especially Down syndrome. In an attempt to increase the number of Down syndrome fetuses being detected and decrease the number of invasive procedures being performed on pregnancies not affected with a chromosome abnormality, both biochemical and ultrasound screening methods are being studied and are summarized in this article. The ultrasound markers reviewed include increased nuchal thickness, increased nuchal lucency, shortened femur, shortened humerus, pyelectasis, hypoplastic ears, echogenic intracardiac focus, hypoplasia of the fifth middle phalanx, and echogenic bowel.

Adverse effects of chorionic villus sampling: a meta-analysis

Meta-analysis is a popular tool for combining evidence from several related studies. The technique is usually used to combine randomized clinical trials, case-control studies or prospective studies where each study has its own exposed and unexposed groups. By including separate 'study effects' (either fixed or random), one can combine information about differences between control and exposed groups, while still allowing for study heterogeneity. In this paper, we extend existing methods to combine studies of disparate designs, where some studies do not include concurrent controls. We apply the methods to a meta-analysis of the association of prenatal testing via chorionic villus sampling with the occurrence of terminal transverse limb defects.

Transcervical recovery of fetal cells from the lower uterine pole: reliability of recovery and histological/immunocytochemical analysis of recovered cell populations

The aim of this work was to isolate, enumerate and attempt the identification of fetal cells recovered from the lower uterine pole. Immediately before elective termination of pregnancy at 7-17 weeks gestation, samples were recovered by transcervical flushing of the lower uterine pole (n = 108) or transcervical aspiration of mucus from just above the internal os (n = 187), and their contents examined using histological, immunohistochemical and molecular techniques. Syncytiotrophoblasts were identified morphologically in 28 out of 89 (31%) and 50 out of 180 (28%) flushings and aspirates respectively (mean 29%). Immunocytochemistry with monoclonal antibodies (mAbs) recognizing trophoblast or epithelial cell antigens on a smaller number of samples (n = 69) identified putative placental cells in 13 out of 19 (68%) and 25 out of 50 (50%) flushings and aspirates respectively (mean 55%). These included groups of distinctive cells with a small, round, hyperchromatic nucleus, strongly reactive with mAbs PLAP, NDOG1 and FT1.41.1. Smaller groups of larger, amorphous cells, usually containing multiple large, pale staining nuclei, reactive with mAb 340 and to a lesser degree with mAb NDOG5 were also observed. Taking cellular morphology and immunophenotype into consideration, the smaller uninucleate cells were likely to be villous mesenchymal cells, while the larger cells were possibly degrading villous syncytiotrophoblast. There was no significant difference in the frequency of fetal cells obtained by the two recovery methods. Squamous or columnar epithelial cells, labelled strongly with antibodies to cytokeratins or human milk fat globule protein, were observed in 97% (29 out of 30) of aspirates. The use of cervagem in a small number of patients prior to termination of pregnancy did not appear to influence the subsequent recovery of placental cells. Y-specific DNA was detected by polymerase chain reaction (PCR) in 13 out of 26 (50%) flushings and (99 out of 154) 64% aspirates analysed (mean 62%). In-situ hybridization (ISH) revealed Y-specific targets in 40 out of 69 (60%) of aspirates analysed. A comparison of PCR data obtained from transcervical recovered samples and placental tissues showed a concordance of 80% (76 out of 95), with 10 false positives. Comparing the PCR data from tissues with data derived by ISH from 41 aspirates gave a concordance of 90% with two false positives. Although syncytiotrophoblasts were much more likely to be present in samples containing immunoreactive placental cells, the detection rates of fetal-derived DNA were similar regardless of the morphological and/or immunological presence of placental cells. We conclude that the transcervical recovery of fetal cells, while promising, requires considerable additional effort being expended in further research and development, particular in the sampling procedure.

Cytogenetic evaluation of 1000 cases of chorionic villus sampling

BACKGROUND

Chorionic villus sampling (CVS) is used routinely as a first trimester diagnostic procedure for fetal karyotyping in at-risk pregnancies. The success of the procedure is dependent on the experience of the operator performing it. The objective of this study was to determine the relationship between an operatorcontrolled clinical and laboratory setting and the safety and reliability of CVS service.

PATIENTS AND METHODS

One thousand patients had a CVS procedure for a variety of indications, such as advanced maternal age, previous child with chromosome abnormality, etc. Both transcervical and transabdominal procedures were performed, according to placental location and uterine environment. For cytogenetic diagnosis, direct and short-term cultures were set up according to standard laboratory protocol.

RESULT

Cytogenetic results were obtained in 99.6% of studies with 94.5% normal (46,XX or 46,XY), with the remaining having a variety of numerical and structural chromosomal abnormalities. Maternal cell contamination was found in 2% of the first 262 cases, while the overall rate observed in the 1000 samples was 0.5%. Level II mosaicism was observed in 0.8% and level III mosaicism observed in 0.9% of cases, respectively. The overall rate of pregnancy loss of chromosomally normal pregnancies within 28 weeks of gestation was 2.8%. No limb reduction defects were seen in any infant post-CVS.

CONCLUSION

Our record demonstrates that experienced operators can deliver a safe and reliable CVS service.

Trends in the use of prenatal diagnosis in New York State and the impact of biochemical screening on the detection of Down syndrome: 1984-1993

Our purpose was to examine trends over time in the use of prenatal cytogenetic diagnosis by New York State women from 1984 to 1993 in the context of new technologies in prenatal diagnosis and pregnancy management. Data are from the New York State Chromosome Registry and represent 95-98 per cent of all New York State women tested. Utilization rates were calculated separately for women under 35 years of age and for those aged 35 years and over. Analysis of longitudinal trends also utilized data from 1979 to 1983. Utilization by women under age 35 increased steadily over time but levelled off after 1986 among older women. Each year, there was an increase in the proportion of tests performed during the first trimester. The proportion of first-trimester tests performed with chorionic villus sampling (CVS) decreased from a maximum of 68 per cent in 1987 to 10 per cent in 1993. The percentage of tests performed due to 'advanced maternal age' decreased over time while 'suspected fetal pathology' categories increased in frequency. The increase in prenatal diagnosis tests performed because of abnormal maternal serum markers was associated with an increase over time in the number and proportion of Down syndrome fetuses detected prenatally and a slight decrease in the prevalence of Down syndrome among live births. The trends reported here parallel improvements in biochemical screening for Down syndrome and published suggestions that all women aged 30 and over are offered prenatal diagnosis.

Chorionic villus sampling

Chorionic villus sampling (CVS) has been used a successful and safe first-trimester prenatal diagnostic technique for over 12 years. Developed to avoid the medical and psychological complications of later prenatal diagnosis by amniocentesis, CVS rapidly has become a primary tool for the diagnosis of fetal cytogenetic, molecular, and biochemical disorders. In addition, its development has led to an improved understanding of several biological processes, including confined placental mosaicism and uniparental disomy.

Chorionic villus sampling and end-artery disruption of the fetus

A fetus with transverse limb reduction defects and jejunal atresia after exposure to chorionic villus sampling (CVS) at 9 weeks of amenorrhoea is described. A theory involving disruption of end-arteries due to the CVS procedure is suggested.

Pregnancy outcome after transcervical CVS with a flexible biopsy forceps: evaluation of risk factors

The pregnancy outcome of 1936 women who had transcervical chorionic villus sampling (CVS) with a flexible biopsy forceps was evaluated. Follow-up until 4 weeks after delivery was 99.4 per cent. Various patient- and procedure-related risk factors for spontaneous loss (fetal or neonatal death) were analysed using stepwise logistic regression analysis. The overall spontaneous loss rate was 4.5 per cent. Factors found to be significantly associated with spontaneous loss were quantity of villi < or = 15 mg (relative risk (RR) 2.13), a history of first-trimester miscarriage (RR 1.87) or delivery between 16 and 27 weeks (RR 3.87), cervical culture positive for anaerobes (RR 4.52) or group B streptococcus (RR 3.62), post-procedural bleeding > 3 days (RR 1.99), and multiple insertions (RR 2.64). Significant differences in loss rates between individual operators were found. A learning effect was not present. There were no infants born with terminal transversal limb anomalies in our series. We conclude that knowledge about significant risk factors for spontaneous loss after CVS is important both for obstetricians carrying out CVS procedures and for women seeking prenatal diagnosis.

Fetal ductus venosus flow velocity waveforms and maternal serum AFP before and after first-trimester transabdominal chorionic villus sampling

Doppler flow velocity waveform recording in the fetal ductus venosus and umbilical artery as well as maternal blood sampling for serum alpha-fetoprotein (MSAFP) was performed before and after transabdominal chorion villus sampling (TACVS) in 36 women of advanced maternal age (> or = 36 years). Gestational age ranged between 11 and 13 weeks. No chromosomal anomaly was detected. No statistically significant difference was observed in ductus venosus velocity parameters or in the umbilical artery pulsatility index (PI) before and after CVS in 35 women with a normal pregnancy outcome. One case resulted in fetal loss. Post-CVS median MSAFP levels at 12 weeks (25 kIU/l) and 13 weeks (35 kIU/l) were significantly higher than pre-CVS levels. In three cases, post-CVS MSAFP levels were higher than 600 kIU/l, correlating with feto-maternal transfusions of approximately 1.0-1.4 ml, i.e., of around 40 per cent of feto-placental blood volume. One of these cases displayed absence of fetal peripheral blood flow velocities and fetal bradycardia following TACVS, resulting in fetal loss 1 week later. The remaining two cases had a normal pregnancy outcome, but showed a more than 50 per cent reduction in ductus venosus velocity after TACVS, whereas umbilical artery PI remained unchanged. However, similar velocity changes were associated with only small feto-maternal transfusions. Umbilical artery PI values remained unchanged.

Increased risk for transverse digital deficiency after chorionic villus sampling: results of the United States Multistate Case-Control Study, 1988-1992

Although numerous infants have been reported with transverse limb deficiencies after their mothers had undergone chorionic villus sampling (CVS), it has been unclear whether the procedure caused these defects. We report the results of the first multistate case-control study to assess and quantify the risk for specific limb deficiencies associated with CVS. Case subjects were 131 infants with nonsyndromic limb deficiency ascertained from 7 population-based birth defect surveillance programs, and born from 1988-1992 to mothers 34 years of age or older. Control subjects were 131 infants with other birth defects. We ascertained exposure to CVS from medical records and maternal and physician questionnaires. We assessed rates and timing of exposure to CVS, and estimated relative and absolute risks for anatomic subtypes of limb deficiency. The odds ratio for all types of limb deficiency after CVS from 8-12 weeks' gestation was 1.7 (95% confidence interval, 0.4-6.3). For specific anatomic subtypes, the strongest association was for transverse digital deficiency (odds ratio = 6.4; 95% confidence interval, 1.1-38.6). The risk for transverse digital deficiency increased with earlier gestational exposure (P < 0.01 for trend). We estimated that the absolute risk for transverse digital deficiency in infants after CVS was 1 per 2,900 births (0.03%). Exposure to CVS was associated with a sixfold increase in risk for transverse digital deficiency. The causality of this association is supported by its strength, specificity, biologic plausibility, and consistency with the results of previous studies. Although some centers already inform patients about risk for limb deficiency, this study quantifies the magnitude of risk associated with CVS from 8-12 weeks' gestation.

Chorionic villus sampling and transverse limb deficiencies: maternal age is not a confounder

Advanced maternal age is a frequent indication for performing chorionic villus sampling (CVS) and it might be a confounder of the association between transverse limb deficiencies (TLD) and early CVS. We have first analyzed the maternal age-specific rates of TLD in the population monitored by the Italian Multicentric Birth Registry; then we updated a case control study controlling for maternal age. The rate of all limb deficiencies (LD) was 5.9 per 10,000 births. No trend for an excess risk for TLD or other LD with advancing maternal age was found. The relative risk for women 35 years of age and older vs. those under 35 was 0.92 (95% CI, 0.72-1.19) for any LD and 0.99 (95% CI, 0.71-1.39) for TLD. In the case control study, 11 mothers of case patients with a TLD had been exposed to CVS out of a total of 206 (5.3%), compared to 54 mothers of control patients with defects other than TLD out of a total of 12,140 (0.4%). The risk estimate for TLD associated with CVS was high in the overall analysis (OR, 12.63) and did not decrease after stratification, both in the overall sample (Mantel-Haenszel OR, 14.01) and in each gestational age stratum. Thus, advanced maternal age does not explain the association between CVS and TLD found in this study and it is unlikely to explain that observed in the several other positive studies. We recommend that any study addressing the relationship between CVS and LD should include a careful evaluation of the type of LD and the timing of CVS, and present the results for specific gestational age periods.