Outcome of first-trimester chorionic villus sampling for genetic investigation in multiple pregnancy.

OBJECTIVES: To evaluate the efficacy of and risk associated with chorionic villus sampling for genetic investigations in multiple pregnancies, and to evaluate the accuracy of the ultrasonographic detection of chorionicity during the first trimester. PATIENTS AND METHODS: A total of 198 sets of twins and nine sets of triplets from 10 087 consecutive first-trimester pregnancies undergoing chorionic villus sampling were considered. Gestational age ranged from 7 to 12.6 weeks. Assessment and confirmation of chorionicity was based on a multiplicity of features. Dichorionicity was established in 169 sets of twins (85.3%) and trichorionicity in all triplet cases, while 29 twins were considered monochorionic. Chorionic villus sampling was performed transabdominally in all but one case, and identification of the placental insertion of the umbilical cord was the main benchmark for sampling. Sampling risks were evaluated by comparing clinical outcome with that of a control population of 63 dichorionic twin pregnancies which underwent no invasive procedure. RESULTS: Determination of the presence or absence of the lambda sign led to a correct assignment of chorionicity in all cases, while the presence of a membrane thickness of 2 mm or more reflected a 100% specificity with a 22% false negative rate. Sampling was successfully performed in all cases and in only four cases (1.0%) were two needle insertions needed. At follow-up no evidence of incorrect sampling was reported. Karyotyping was provided to all patients, and in 94.1% of cases both short and long-term culture methods were carried out. No difference in fetal and perinatal losses between the study and control populations was found, but a higher rate of deliveries before 37 weeks and of low birth weight babies was noted amongst controls. CONCLUSIONS: Chorionicity in twin pregnancy can be determined with certainty between 7 and 12 weeks of gestation; in cases of confluent placentas reliability is provided by determining the presence or absence of the lambda sign. This study indicates that first-trimester transabdominal chorionic villus sampling is a highly efficient, reliable, and relatively safe approach for genetic diagnosis in twin pregnancies. Although a precise evaluation of the relative risks of chorionic villus sampling and mid-trimester amniocentesis in twins must await randomized control studies, the advantages of a first-trimester diagnosis to enable early decision-making about selective fetal reduction are obvious.

RhD genotyping by quantitative fluorescent polymerase chain reaction: a new approach.

OBJECTIVE: To develop a new method of RhD/d genotype determination using a quantitative fluorescent PCR (QF-PCR) assay. METHODS: Polymerase chain reaction amplification (PCR) of fragments of exon 7 of both the RHD and RHCE genes was performed from 32 amniotic fluid and 26 chorionic villus samples known to be heterozygous for the RHD gene, 74 peripheral blood samples of RhD-positive blood donors (homozygous or heterozygous) estimated by serologic typing and 24 RhD-negative fetal samples. The number of copies of the RHD gene in RhD-positive samples was determined by comparing the fluorescent intensities of the amplification products specific for the RHD and the RHCE genes. RESULTS: A ratio of fluorescent intensities of 1:1 clearly indicated D/D homozygous individuals whereas a ratio of 1:2 was demonstrated in samples from D/d heterozygous individuals. The mean fluorescent intensity ratio of the peak areas of homozygous samples was 1.12 (SD 0.128), the mean ratio of the peak areas of heterozygous samples was 0.51 (SD 0.060). Complete agreement was obtained between RhD/d typing by QF-PCR and RhD genotypes assessed by family studies and serological methods. CONCLUSIONS: The fluorescent PCR-based DNA test allows easy, rapid and accurate determination of the zygosity for the RHD gene. This new technique provides useful information for the clinical management of pregnancies of sensitised RhD-negative mothers.

Rapid detection of chromosome aneuploidies by quantitative fluorescence PCR: first application on 247 chorionic villus samples.

We report the results of the first major study of applying quantitative fluorescence polymerase chain reaction (QF-PCR) assays for the detection of major chromosome numerical disorders. The QF-PCR tests were performed on a total of 247 chorionic villus samples, which were analysed blind, without any knowledge of the results obtained using conventional cytogenetic analysis. The aims of this investigation were to evaluate the detection power and accuracy of this approach by testing a large number of fetal samples and to assess the diagnostic value of each of the chromosome specific small tandem repeat (STR) markers used. In addition, we introduced three more markers specific for chromosomes 13, 18, and X to allow an accurate analysis of samples homozygous for a particular STR. Fluorescent labelled primers were used to amplify 12 STRs specific for chromosomes 21, 18, 13, X, and the amylogenin-like DNA sequence AMXY, expressed on the X and Y chromosomes. In this blind study of 247 fetal samples, 222 were correctly diagnosed by QF-PCR as normal for each of the five chromosomes investigated; 20 were diagnosed by QF-PCR as trisomic for chromosomes 21, 18, or 13, in agreement with the cytogenetic tests. Only one false negative result was observed, probably owing to the mishandling of the sample, which had been transferred through three laboratories before being analysed by QF-PCR. The 247 samples also included four cases of mosaicism or translocation; one case of mosaic trisomy 21 was detected by QF-PCR and the other cases were not identified by QF-PCR. The results of this investigation provide clear evidence that the QF-PCR assays are powerful adjuncts to conventional cytogenetic techniques and can be applied for the rapid and accurate prenatal diagnosis of the most frequent aneuploidies.

Comparison of urinary free beta (hCG) and beta-core (hCG) in prenatal screening for chromosomal abnormalities.

To evaluate the potential utility of free beta (hCG) and beta-core (hCG) in a prenatal screening protocol for Down syndrome we analysed these markers in dried maternal urine specimens from 163 control, 13 Down syndrome and 5 trisomy 18 pregnancies from 8 to 25 weeks' gestation. All results are reported after normalization for urinary creatinine determined by modified Jaffe reagent assay. The correlation of urinary free beta (hCG) and urinary beta-core (hCG) was 0.61 in controls and 0.93 in Down syndrome. Median MoM values in Down syndrome were 2.42 for urinary free beta (hCG) and 2.40 for beta-core (hCG). In trisomy 18 the Median MoM was 0.35 and 0.34 for free beta (hCG) and beta-core (hCG), respectively. The degree of elevation observed in DS cases with urinary free beta (hCG) is consistent with previous reports. Studies of beta-core (hCG) in Down syndrome have yielded discrepant results. In this study, beta-core (hCG) in Down syndrome is lower than values observed in early reports but consistent with more recent reports.

First 10,000 chorionic villus samplings performed on singleton pregnancies by a single operator.

Chorionic villus sampling (CVS) was performed in 10,000 consecutive singleton pregnancies by a single principal operator, working in two institutions. The procedure was performed between 8 and 32 gestational weeks: transabdominal (TA) sampling was carried out in 8479 cases and transcervical (TC) in 1521. Patients were referred for chromosomal risk in 89.1 per cent of cases, Mendelian disorders in 10.5 per cent, and DNA investigations for paternity or infectious agents in 0.4 per cent of cases. The sampling success rate for both TA and TC techniques by the second insertion was 99.8 and 99.2 per cent, respectively. TA sampling succeeded in a higher number of cases at the first insertion (98 per cent vs. 86.8 per cent) and was associated with smaller samples (< 10 mg) in fewer cases (3.2 per cent vs. 4.9 per cent). Cytogenetic analysis was highly successful (99.4 per cent) and accurate; however, in one case a de novo structural rearrangement of chromosome I was not recognized. Mosaicism or rare trisomies were reported in 1.30 per cent of cases. Five diagnostic errors in DNA investigation (0.51 per cent) ended with the birth of affected fetuses. Fetal loss through 28 weeks' gestation in the pregnancies intended to continue was 2.58 per cent; the rate increased with maternal age (1.22 per cent at less than 30 years to 3.8 per cent at 40 years or more), while gestational age affected the abortion rate only at 8 weeks (odds ratio=2.22, P<0.05). Rates of premature delivery, low birth weight, and perinatal mortality did not differ from the Italian standards. By comparison with the Italian Birth Defects Registry data, no differences were found for the major malformations, including transverse limb reduction defects (TLRDs) (4.34 vs. 3.28 x 10,000). Total malformations and TLRDs did not show any pattern relation to either maternal age or gestational age.

Prenatal cystic fibrosis screening in a low-risk population undergoing chorionic villus sampling for fetal karyotyping.

Screening for cystic fibrosis (CF) has been offered to pregnant women seeking chorionic villus sampling (CVS) for prenatal chromosomal abnormality investigation. The mutation panel has increased over the years to include 8 mutations and can detect 65% of abnormal CF genes in the Italian population. Testing was offered to a total of 2214 consecutive pregnant women; 45 of them declined screening (take up rate: 98%). In 1055 of the 2169 pregnancies screened, the test was at first done on the fetus, while in the remaining cases both parents were investigated. Among parents 46 carriers were identified (2.1%), in 41 of whom the mutation was delta F508. In two couples both parents were heterozygous, and in one the fetus was affected and the pregnancy was terminated. Although CF testing offered to pregnant women undergoing invasive investigation such as CVS may not be the model for a mass screening, its very high effectiveness can represent an advantageous component of more comprehensive strategies.

Prenatal diagnosis by chorionic villus sampling.

Chorionic villus sampling (CVS) retains its great advantage over mid-trimester amniocentesis by producing early results. Moreover, rapid analytical techniques reduce significantly the waiting time between sampling and diagnosis, while recombinant DNA technology and human gene mapping progress amplify enormously the spectrum of the indications. The recent inclusion in the prenatal diagnosis package of screening tests based on DNA analysis for the major genetic diseases (i.e. cystic fibrosis, fragile-X mental retardation syndrome) may efficiently contribute to prevent the genetic disease. The role of CVS in twin pregnancy has been investigated and compared to amniocentesis. Although these techniques are equally safe, CVS should be considered the approach of choice for a number of technical advantage and in relation to selective fetal reduction in discordant twins. Recent reports have substantially contributed on the hypothetical relationship between limb reduction defects (LRDs) and chorion biopsy. The analysis of LRDs among more than 130,000 CVS reported to WHO CVS-Registry has been unable to find out any relationship between sampling and fetal malformations, including LRDs. In conclusion, first trimester CVS should be considered the gold standard procedure for prenatal diagnosis of genetic diseases.

International, collaborative experience of 1789 patients having multifetal pregnancy reduction: a plateauing of risks and outcomes.

OBJECTIVE: To develop the most up-to-date, complete data base of multifetal pregnancy reduction (MFPR) from cases, and to provide the best counseling for couples with multifetal pregnancies. METHODS: From nine centers in five countries, 1789 completed MFPR cases were collected and outcomes evaluated. Pregnancy losses were defined as through 24 weeks and deliveries categorized in groups of 25-28, 29-32, 33-36, and 37 or more weeks. RESULTS: Overall, the pregnancy loss rate was 11.7% but varied from a low of 7.6% for triplets to twins and increased with each additional starting number to 22.9% for sextuplets or higher. Early premature deliveries (25-28 weeks) were 4.5% and varied with starting number. Loss rates by finishing number were highest for triplets and lowest for twins, but gestational age at delivery was highest for singletons. CONCLUSIONS: Multifetal pregnancy reduction has been shown to be a safe and effective method to improve outcome in multifetal pregnancies. Outcomes are worse with higher-order gestations and support the need for continued vigilance of fertility therapy.

First trimester fetal reduction: its role in the management of twin and higher order multiple pregnancies.

Multiple pregnancy may be the result of stimulated or non-stimulated, and of assisted or natural conception. As observed in the past decade, assisted conception technologies have significantly increased the prevalence of multiple pregnancy. The increase has been much more marked for triplets and higher order births. Rates of perinatal mortality and fetal and maternal complications are higher in twins than in singletons, and the adverse outcome rises with increasing number of multiples. Unplanned multiple pregnancy may be felt to be emotionally and physically so stressful an experience as to drive patients to refusal of pregnancy itself, or to want to reduce the number of fetuses to an acceptable standard. Fetal reduction techniques have emerged as a very effective medical approach to improve pregnancy outcome and a key option of patients trying to carry a pregnancy to term. Multiple fetuses are most frequently heterozygotes; therefore the risk of each of them being affected by a Mendelian disease or sporadic chromosomal aberration is an independent probability. Thus, the incidence of genetic defects in at least one fetus is increased and directly related to the order of multiples, and this makes it worthwhile to offer karyotyping of the fetus(es) to be spared, before the reduction procedure takes place. When a multiple pregnancy is established, one may conclude selective reduction is the most effective therapeutic approach for reducing risks.

Genetic analysis prior to selective fetal reduction in multiple pregnancy: technical aspects and clinical outcome.

Multiple pregnancies resulting from ovarian stimulation are at a higher risk of carrying at least one fetus affected by Mendelian or chromosomal anomalies, the incidence of which is directly related to the order of multiples. Genetic analysis before fetal reduction was offered to both high- and low-risk pregnant women carrying two or more fetuses after ovulation induction. Chorionic villus sampling (CVS) and fetal reduction were achieved by transabdominal needling. The use of short-term culture, the polymerase chain reaction and fresh tissue enzymatic analyses have made it possible for genetic diagnosis to be available in a few days. A total of 100 patients had multifetal pregnancy reduction performed by a single operator; all of them completed pregnancy and none was lost at follow-up. The total fetal loss before 24 weeks was 7% and no statistically significant relationship was found with the final number of fetuses and CVS. Perinatal losses (3.9%) were only present in the series with a final number of two fetuses. Pregnancy duration and birthweight were significantly higher in singletons than in twins, but were not related to CVS. The rate of chromosomal disorders was higher (7.2%) in the study series than in singleton pregnancies not undergoing fetal reduction. Diagnostic error due to incorrect sampling was reported in 1.5% of cases. These data support fetal reduction as a valuable strategy to improve the outcome of multiple pregnancy. The outcome of pregnancies reduced to singletons was significantly better than of those reduced to twins, and was not related to CVS.(ABSTRACT TRUNCATED AT 250 WORDS)

First-trimester Down's syndrome screening using nuchal translucency: a prospective study in patients undergoing chorionic villus sampling.

The value of the measurement of nuchal translucency thickness for predicting fetal Down's syndrome and other aneuploidies was prospectively evaluated at 8-15 weeks of gestation in 1819 consecutive pregnancies scheduled for karyotyping by chorionic villus sampling. In 43 cases, a chromosomal unbalanced aberration was found. Two teams of ultrasonologists who examined patients attending either National Health Service (Series 1) or private practice clinics (Series 2) were involved in the study. The same type of ultrasound machine and standardized approach were used in both study groups. In those cases in which the maximum subcutaneous thickness of the translucency was 3 mm or greater, the incidence of chromosomal aberration was 18.6% compared to 1.7% in the cases in which this was below 3 mm. The sensitivity, specificity and relative risk for all aneuploidies were 30%, 96% and 10.83, respectively, and no difference was found between trisomy 21 and other types of aneuploidy. The sensitivity and specificity and relative risk were significantly higher at 9-10 weeks than between 11 and 15 weeks. The results were concordant in the two series; however, the overall values for sensitivity (20% vs. 39%), specificity (94% vs. 98%) and relative risk (4.13 vs. 24.20) were clearly higher in the group of private patients. The results obtained confirm the potential application of the measurement of nuchal translucency thickness for fetal aneuploidy screening before the end of the first trimester and suggest that a multiplicity of individual, structural and organizational factors may interact and play a crucial role in determining the actual efficiency of ultrasound screening programs.

Serum PAPP-A and free beta-hCG are first-trimester screening markers for Down syndrome.

Serum measurements of pregnancy-associated plasma protein A (PAPP-A) and the free beta-human chorionic gonadotrophin (hCG) subunit were made in 13 women with Down syndrome (DS) pregnancies and six other women with fetal aneuploidy ascertained at chorionic villus sampling (CVS), as well as 89 women with contemporaneous normal control pregnancies. Median serum PAPP-A measurements (0.31 MOM, 95 per cent confidence interval (CI) 0.22-0.65 vs. normal 1.06, 95 per cent CI 0.89-1.20) were lower and free beta-hCG subunit measurements (1.13 MOM, 95 per cent CI 0.93-2.63 vs. normal 0.91, 95 per cent CI 0.79-1.03) were higher at statistically significant levels. Receiver operator characteristics (ROC) curves showed that the highest sensitivity for detection, 71.2 per cent (95 per cent CI 54.7-87.6 per cent), was for depressed PAPP-A levels; the combination of low serum PAPP-A levels, maternal age, and elevated free beta-hCG levels yielded a detection rate of 78.9 per cent (95 per cent CI 64.9-92.8 per cent) of the affected pregnancies at 8-12 weeks' gestation.

Multiple pregnancy induction and selective fetal reduction in high genetic risk couples.

Couples at risk for an inherited disorder often have several pregnancy interruptions because of affected fetuses and difficulty in achieving their desired family. We evaluated the efficiency and acceptability of selective fetal reduction after chorionic villus sampling (CVS) of multiple pregnancy induced by ovarian stimulation and gamete intra-Fallopian transfer (GIFT). This approach has been offered to nine patients at risk of Mendelian diseases and one patient carrier of reciprocal translocation. The acceptance has been very high (90%). One patient at risk of an autosomic recessive disease opted for artificial donor insemination, one conceived spontaneously, and one was a poor responder to ovarian stimulation. Seven patients actually underwent a single GIFT procedure with six achieving pregnancy (86%), all but two being a multiple pregnancy (67%). All pregnancies concluded uneventfully at term and newborns were alive and healthy. Prenatal diagnosis, including fetal karyotyping in all cases, was performed at 8.5-11.5 weeks of gestation and confirmed either on amniotic fluid aspirated at reduction or at birth. The number of fetuses was reduced to one or two because the genetic disease was present and/or to reduce the risk of premature delivery and improve the likelihood of successful pregnancy. The new approach seems to be highly effective and might be considered a practical and useful alternative to preimplantation genetic diagnosis.

Low maternal serum levels of pregnancy associated plasma protein A (PAPP-A) in the first trimester in association with abnormal fetal karyotype.

OBJECTIVE: To assess the relation between maternal serum pregnancy associated plasma protein A (PAPP-A) in the first trimester and the outcome of pregnancy by karyotype. DESIGN: A retrospective study of PAPP-A levels in blood samples collected prior to chorionic villus sampling. SETTING: Milan, Italy. SUBJECTS: Five hundred twenty-two women aged 20 to 47, at 7 to 11 weeks gestation, prior to undergoing chorionic villus sampling. Four hundred forty-five women had a pregnancy with a normal karyotype; in 30 pregnancies the karyotype was abnormal (including 14 cases of Down's syndrome and 7 of trisomy 18). MAIN OUTCOME MEASURES: Normal or abnormal fetal karyotype. Serum PAPP-A at 6 to 11 weeks gestation measured by radioimmunoassay. RESULTS: The median value of PAPP-A in the abnormal group was 0.27 multiples of the normal median (MoM). This is significantly lower than the median value in the normal group (1.01 MoM) (95% CI for the difference 0.46-0.84 MoM; P < 0.00001 Mann-Whitney test). CONCLUSIONS: There is an association between low levels of PAPP-A in the first trimester with chromosome anomalies. Screening by measurement of PAPP-A might detect 60% of cases of Down's syndrome in the first trimester with a false positive rate of 5%.

Genetic diagnosis by chorionic villus sampling before 8 gestational weeks: efficiency, reliability, and risks on 317 completed pregnancies.

Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6-7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent of cases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS.

First-trimester genetic diagnosis in multiple pregnancy: principles and potential pitfalls.

Both the principles of first-trimester genetic diagnosis in multiple pregnancy and the special considerations required to avoid potential diagnostic pitfalls are presented. The experience consisted of 65 cases of twins and one case of quadruplets. Dichorionic twins were recognized by sonography in 54 cases. Transabdominal aspiration was generally preferred to transcervical for obtaining chorionic tissue, although in two cases both approaches were used. Diagnostic error following erroneous sampling was reported in 3 out of 54 sets of dichorionic twins (5.5 per cent). When like-sex dichorionic twins cannot be differentiated by cytogenetic or DNA polymorphism studies, amniocentesis should be recommended to confirm the reliability of the result on chorionic tissue.