Transverse limb reduction defects after chorion villus sampling: a retrospective cohort study. GIDEF--Gruppo Italiano Diagnosi Embrio-Fetali

Chorionic villus sampling: A distinctive teratogenic effect on fingers?

BACKGROUND

An increased frequency of major limb malformations, especially terminal transverse limb defects, have been described in several studies of birth defects in children who had been exposed to the prenatal diagnosis procedure known as chorionic villus sampling (CVS). Vascular disruption has been proposed as the mechanism behind the fetal effect. We postulate that this mechanism is more likely to affect one or two middle fingers, rather than all five fingers. A recent report of the frequency of defects in any or all fingers in an unexposed control population enabled us to assess whether CVS is associated with an increased frequency of defects involving one or two fingers, as well as terminal transverse limb defects.

METHODS

The frequency of limb-reduction defects affecting one or more fingers or toes, including those with constriction rings and tissue loss, in published studies of 20,236 children who had been exposed to CVS was compared with the frequency in 161,252 newborn infants who had not been exposed to CVS. Children with recognized genetic disorders were excluded.

RESULTS

Several aspects of the limb deficiencies were more common in the CVS-exposed infants than in unexposed controls. The former were more likely to have: 1) any type of limb deficiency involving one or more fingers (p < .001); 2) absence/ hypoplasia of two fingers (p < .001); and 3) absence/hypoplasia of all five fingers (p = .015). The absence of the distal portion of the third finger was a distinctive type of limb-reduction defect in CVS-exposed infants.

CONCLUSIONS

The occurrence of deficiencies in one or two fingers, including those designated as "amniotic band deformities," are as common as terminal transverse limb defects in CVS-exposed infants, and both are much more common than in unexposed infants. The absence of the distal portion of the third finger, with tapering and stiff joints, appears to be a distinctive effect of exposure to CVS.

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.

What invasive procedure to use in early pregnancy?

As scientific knowledge and medicine advance so do the expectations of the general public. Advances in molecular biology, ultrasonography, access to the early gestational sac and prenatal diagnosis have helped both drive and meet these expectations. We discuss the use, advantages, potential risks and complications of invasive prenatal diagnostic procedures in early pregnancy. All invasive procedures should be performed under continuous ultrasound guidance by experienced operators. Within this context, mid-trimester amniocentesis remains the safest invasive procedure. Chorionic villus sampling (CVS) and early amniocentesis (EA) are associated with a higher risk of subsequent pregnancy loss. There is also a 10-fold increase in the risk of mosaicism with CVS compared to amniocentesis. Both CVS and EA can induce fetal structural defects and should be abandoned as routine invasive tests. Patient counselling should include an evaluation of the risk associated with each individual procedure but also the operator's personal complication rate.

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.

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.

CVS-exposed limb deficiency defects with or without other birth defects: presentation of six cases born during a period of nine years

We report on six cases with CVS-exposed limb-"reduction" defects born in our hospital during a period of 9 years (1986-1994). Four cases were associated with other birth defects. One had an oromandibular-limb hypogenesis syndrome with a cleft lip and jejunal atresia, a second had an oromandibular-limb hypogenesis (Hanhart) syndrome, a third had severe flexion deformity at the hips and hyperextension at the knees with meconium peritonitis and intestinal obstruction, and a fourth had Poland anomaly. Detailed clinical descriptions, prenatal diagnosis, photographs, and radiographs are presented. Our presentation adds to the information on severe limb abnormalities after CVS and suggests CVS-exposed limb defects may be associated with other birth defects resulting from vascular insufficiency or intrauterine compression. We suggest that detailed post-CVS sonographic followups are necessary for each CVS-exposed case to identify not only the possible fetal limb reduction, but also vascular disruption-type malformations and compressive deformities.

Chorionic villus sampling and transverse digital deficiencies: evidence for anatomic and gestational-age specificity of the digital deficiencies in two studies

Several but not all studies indicate that chorionic villus sampling (CVS) is associated with an increased risk for transverse limb deficiencies, including digital deficiencies. It has been suggested that variations in results regarding the transverse digital deficiencies (TDDs) may be due to the use of different classification criteria. We present the combined analysis of two case-control studies, the U.S. Multistate CVS (US) study and the Italian Multicentric Birth Defects (IP-IMC) study, using two different definitions of TDDs. We compared the frequency of CVS exposure in control infants with that among those infants with any number of affected digits (any TDD), and those with all five digits of at least one limb affected (extensive TDDs). The estimated relative risk (RR) for any TDD following CVS was 10.6 (IPIMC) and 6.6 (US). For the extensive TDDs, the RR was 30.5 (IPIMC) and 10.7 (US). In both studies, extensive TDDs were less than 25% of all TDDs. Compared to all TDDs, extensive TDDs were more likely to occur after CVS performed earlier in the first trimester (before 10-11 weeks' gestation). These findings suggest a relationship between the timing of CVS and the severity of TDDs; indicate that using a restrictive definition of TDDs (all five digits affected) may limit the ability to evaluate the association between CVS and TDDs in populations in whom CVS is usually performed at or after 10 weeks' gestation; and highlight the necessity to consider gestational age in any evaluation of the relative risk for limb deficiencies associated with CVS.

Immediate changes in umbilical blood flow after transcervical chorionic villus sampling performed by biopsy forceps

Transvaginal ultrasonography with colour Doppler was used to evaluate the immediate changes on the fetal heart rate (FHR) and the fetal umbilical artery pulsatility index (PI) after chorionic villus sampling (CVS). This prospective study included 279 consecutive singleton pregnancies, between 10 and 13 weeks, of women who underwent transcervical CVS in our institution. All Doppler measurements were obtained transvaginally before and immediately after CVS. Structural malformations detected by ultrasound were excluded. Student's t- and Wilcoxon texts were performed for statistical analysis. The results showed no significant decrease in FHR (mean 1.04 beats, t = 1.68, P = 0.94) and a significant elevation of umbilical artery PI (mean 0.12, t = - 6.51, P < 0.001) post-CVS. This difference was only significant in procedures performed at less than 11 weeks' gestation, since there was no significant change for those procedures performed thereafter. These preliminary data suggest that acute fetal haemodynamic changes are induced by CVS and may have clinical effects. Hypotheses on possible vascular mechanisms are discussed. Colour Doppler could widen the possibilities for more accurate in vivo assessment and research on CVS-related placental injury.

Limb defects and chorionic villus sampling: results from an international registry, 1992-94

BACKGROUND

Several reports of limb defects occurring among infants exposed to chorionic villus sampling (CVS) during pregnancy resulted in concern about the safety of this procedure for prenatal diagnosis. To avoid publication bias and evaluate the true risk of limb defects in a CVS cohort, the World Health Organization initiated international registration of post-CVS limb defects in 1992.

METHODS

From May, 1992, to May, 1994, 77 infants or fetuses with limb defects from 138 996 pregnancies having CVS were reported to the WHO CVS Registry. These cases were analysed by standardised methods-ie, exclusion of syndromes, inherited disorders, and defects occurring in previable fetuses. The included limb deficiencies were studied by pattern analysis.

FINDINGS

Defects of the upper limbs were reported in 64.6%, of the lower limbs in 12.5%, and of both upper and lower limbs in 20.8% of cases. These figures are in agreement with the distribution of limb defects in several large population-based studies. Transverse limb defects occurred in 40.8% and longitudinal defects in 59.2%, compared with 42.7% and 57.3% in an unexposed population.

INTERPRETATION

The analysis of this cohort did not show any differences from the background population in the overall frequency or pattern distribution of limb deficiencies. There was also no correlation between gestational age at CVS and severity of defects. Therefore these results do not indicate any increased risk of limb defects after CVS.

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.