Chorionic villus sampling and amniocentesis.

PURPOSE OF REVIEW: The advantages and disadvantages of common invasive methods for prenatal diagnosis are presented in light of new investigations. RECENT FINDINGS: Several aspects of first-trimester chorionic villus sampling and mid-trimester amniocentesis remain controversial, especially fetal loss rate, feto-maternal complications, and the extension of both sampling methods to less traditional gestational ages (early amniocentesis, late chorionic villus sampling), all of which complicate genetic counseling. A recent randomized trial involving early amniocentesis and late chorionic villus sampling has confirmed previous studies, leading to the unquestionable conclusion that transabdominal chorionic villus sampling is safer. The old dispute over whether limb reduction defects are caused by chorionic villus sampling gains new vigor, with a paper suggesting that this technique has distinctive teratogenic effects. The large experience involving maternal and fetal complications following mid-trimester amniocentesis allows a better estimate of risk for comparison with chorionic villus sampling. SUMMARY: Transabdominal chorionic villus sampling, which appears to be the gold standard sampling method for genetic investigations between 10 and 15 completed weeks, permits rapid diagnosis in high-risk cases detected by first-trimester screening of aneuploidies. Sampling efficiency and karyotyping reliability are as high as in mid-trimester amniocentesis with fewer complications, provided the operator has the required training, skill and experience.

The use of non-physiological conditions to isolate fetal cells from maternal blood.

Fetal cells are always present in maternal blood starting in the first trimester of pregnancy, however a rapid, simple, and consistent procedure for their isolation for prenatal non-invasive genetic investigation is still lacking. Sensitivity and recovery of fetal cells is jeopardized by the minute amount of circulating fetal cells and their loss during the enrichment procedure. We report here a single-step approach to isolate fetal cells from maternal blood which relies on the use of non-physiological conditions to modify cell densities before their separation in a density gradient and in a newly developed cell separation device. Isolated fetal cells have been investigated using cytochemistry, Soret band absorption microscopy, monoclonal antibodies for epsilon- and gamma-chain-Hb, monoclonal antibody for i-antigen, and by fluorescence in situ hybridization (FISH). Fetal cells were always detected in all 105 maternal blood samples investigated and fetal aneuploidies were correctly diagnosed by FISH, in a pilot study of pathological pregnancies, in fetal cells isolated from maternal blood obtained either before or after invasive procedure.

First-trimester fetal reduction to a singleton infant or twins: outcome in relation to the final number and karyotyping before reduction by transabdominal chorionic villus sampling.

OBJECTIVE: The purpose of this study was to evaluate fetal outcome and maternal complications of multifetal pregnancy reduction to a single fetus or twins. To evaluate safety and efficacy of transabdominal chorionic villus sampling for karyotyping before fetal reduction. STUDY DESIGN: Four hundred twenty-four consecutive multiple pregnancies were reduced to twins (255 pregnancies) or a single fetus (169 pregnancies) at 8 to 13 weeks of gestation after transabdominal chorionic villus sampling for fetal karyotyping. Fetal and maternal outcome were observed prospectively and compared with control series of twin (147) and singleton (885) pregnancies in which reduction procedures were not performed. RESULTS: Transabdominal chorionic villus sampling was performed successfully in 100% of the cases. The accuracy of karyotyping was 99.2%. The overall pregnancy loss rate after reduction was 3.3%. No differences were observed between study and control series for severe prematurity, low birth weight, and neonatal deaths. Mean gestational age at delivery (35.2% vs 38.1%) and mean birth weight (2180 g vs 2873 g) were significantly lower; preterm delivery (64% vs 11%), neonatal death (3.4% vs 0.6%), and maternal complications (42.8% vs 9.5%) were significantly higher when the reduction was to twins rather than in reduction to a single fetus. Pregnancy loss rate did not differ between study series. The overall rate of chromosomal abnormalities in the study series was higher (relative risk, 2.0) than in singleton control series. CONCLUSION: The outcome of multiple pregnancies that were reduced to a single fetus or twins was similar to that of nonreduced pregnancies; fetal and maternal complications were significantly lower in the series of pregnancies that were reduced to a single fetus. The safety and efficacy of transabdominal chorionic villus sampling and the higher pregnancy rate of chromosomal abnormalities in multiple pregnancies imply that fetal karyotyping should be advised before fetal reduction.

First-trimester prenatal screening for the common 35delG GJB2 mutation causing prelingual deafness.

OBJECTIVE: This study evaluates the prevalence of 35delG GJB2 mutation, the most common genetic mutation causing prelingual deafness, and its screening feasibility and acceptability in pregnant women undergoing first-trimester CVS for chromosomal abnormality investigation. METHODS: Samples were taken from 5786 pregnant women who requested CVS for chromosomal analysis. The samples were split into two aliquots for chromosome and DNA analysis, respectively. The results of foetal karyotyping were provided 7 days after sampling, at which time the fully informed couple decided whether or not to undergo DNA testing. RESULTS: Of the 5449 eligible candidates, 2997 (55.0%) chose to undergo 35delG testing. Among them, 67 proved to be carriers of the mutation, resulting in a prevalence rate of 1:44.7 (2.23%). There were no homozygous foetuses, but two double heterozygous foetuses were found, and in one case the couple chose to terminate the pregnancy. CONCLUSIONS: The results confirm the high frequency of 35delG mutation in the Italian population. The study shows that prenatal screening for GJB2 mutations in pregnant women with no retrospective risk for deafness appears to be feasible and highly acceptable. Consequently, given evidence that early evaluation and treatment significantly improve speech and language skills, as well as social and emotional well-being in affected children, 35delG mutation analysis in pregnant women booking CVS primarily for chromosomal investigation could be considered a useful addition to more comprehensive population screening strategies.

Early second trimester (13 to 20 weeks) transabdominal chorionic villus sampling (TA-CVS): a safe and alternative method for both high and low risk populations.

OBJECTIVE: To assess feasibility, effectiveness and risk of prenatal diagnosis by TA-CVS at 13-14 and 15-20 weeks' gestation. METHODS: CVS was performed transabdominally by free-hand single needle insertion technique under continuous ultrasound visualization on 1844 pregnant women, aged 18 to 48, at 13 to 20 weeks' gestation, whose primary indication was chromosomal anomalies and single gene defects in 85% and 15% of cases, respectively Clinical follow-up of women undergoing TA-CVS at 13 to 20 weeks' was prospectively obtained; the population was split in two groups of 13-14 (series B) and 15-20 weeks' (series C) gestation. Statistical evaluation included a group of TA-CVS cases performed at 11-12 weeks (series A). RESULTS: Sampling was feasible in 98.2%, 99.1% and 95.8% of cases of series A, B and C, respectively. Sampling was successful in all cases of the three series and a second insertion was required in 1.5%, 1.3% and 0.9%, respectively. A trend towards lower fetal loss rate is apparent (1.02%, 0.86%, and 0.46 in series A, B, and C, respectively), although differences were not statistically significant. No post-procedural complications were reported for series B and C, while spotting was present in 1.8% of cases for series A. Karyotyping was totally successful by short term culture and was also available by long term culture in 99% of cases for series A, B and C when the amount of chorionic tissue was more than 15 mg. CONCLUSION: TA-CVS appears highly effective and safe and might be offered as a valuable alternative to early as well as mid-trimester amniocentesis.