Prospective study of amniocentesis performed between weeks 9 and 16 of gestation: its feasibility, risks, complications and use in early genetic prenatal diagnosis

Genetic amniocentesis using atraumatic 29 gauge needle in patients having a chorioamniotic separation

OBJECTIVES

Chorioamniotic separation (CAS) at the time of standard amniocentesis (AC) is a risk factor for postprocedural complications and should be avoided. The aim of this study was to quantify procedure-related risks after AC with a 29G-needle in cases of CAS, and evaluation of perinatal outcome in CAS after 15 weeks' gestation (GW).

METHODS

Retrospective analysis of genetic AC with a pencil-point 29G needle after 15 completed GW in pregnancies, in which the fetal membranes were not yet fused. Included into the study were women aged 16-44 years with at least 15 completed GWs referred for second trimester AC to identify fetal chromosomal aberrations.

RESULTS

437 ACs were made in total with the 29G-needle. The median maternal age was 30 (16-44) years. 145 cases showed CAS where the distance between chorion and amnion was 0.10-10.02 mm at AC. 38 pregnancies were terminated, 37 of which had a genetic disorder. The risk of aneuploidy increases by a factor of 2 (95% CI 1.4-2.8) for every 1 mm of CAS enlargement. No procedure-related complications were found up to two weeks after the AC.

CONCLUSIONS

CAS seems to be massively underreported. Early diagnosis in case of CAS is something to strive for as CAS could be an indicator of genetic abnormalities - a "soft marker". With the atraumatic 29G needle, the risk of complications after AC in CAS seems to be very low.

Amniopatch treatment of iatrogenic preterm premature rupture of membranes (iPPROM) after fetoscopic laser surgery for twin-twin transfusion syndrome

OBJECTIVES

Amniopatch is a proposed treatment of iatrogenic preterm premature rupture of membranes (iPPROM). We studied characteristics associated with successful amniopatch treatment of iPPROM after fetoscopic laser surgery for twin-twin transfusion syndrome.

METHODS

Patients with iPPROM within 15 days of laser surgery treated with an amniopatch were studied. Factors associated with amniopatch success (i.e. cessation of leakage with normalization of amniotic fluid volume) were tested univariately and in multivariate logistic regression models. Continuous variables are expressed as median (range).

RESULTS

Of 1124 patients undergoing laser surgery, 19 (1.7%) had iPPROM and subsequent amniopatch. Twelve (63.2%) were successful. Latency in days from iPPROM to delivery was greater in the successful group (114.0 [87.0-141.0]) versus (44.0 [3.9-88.0], p = 0.0005), which translated into greater gestational age (GA) (weeks) at delivery (35.1 [30.9-39.4] versus 28.1 [22.0-31.0], p = 0.0005). The 30-day survival of the affected recipient twin was improved (100% versus 57.1%, p = 0.0361). After multivariate testing, GA < 20 weeks at the time of the amniopatch placement was the only variable that remained associated with successful sealing of the membranes.

CONCLUSIONS

Treatment of iPPROM via amniopatch was successful in almost two-thirds of cases and was associated with higher GA at delivery and improved perinatal survival.

Rapid and novel prenatal molecular assay for detecting aneuploidies and microdeletion syndromes

OBJECTIVES

To develop a targeted aneuploidy and microdeletion detection platform for use in the prenatal setting, to assess the integrity of the platform with a robust validation system, and to prospectively determine the performance of the platform under routine clinical conditions.

METHODS

To generate proxies for the various disorders assessed by the assay for analytical validation purposes, cells from ten microdeletion syndromes as well as from common aneuploidies were spiked into cleared amniotic fluid. Genomic DNA was isolated, labeled, and hybridized to microbeads that have been coupled to DNA derived from Bacterial Artificial Chromosome (BAC) from the relevant regions targeted by the array. Beads were read using a flow cytometric multiplex bead array detection system. In the prospective part of the study, 104 amniotic fluid samples were collected and analyzed.

RESULTS

All microdeletion syndromes and aneuploidies were validated in a blinded fashion. In the prospective study, the total number of readable samples was 101 of 104 (97%). All sample results were confirmed independently.

CONCLUSION

The bead array approach is a rapid and reliable test for detecting aneuploidies and microdeletions. This assay has the potential to provide the benefit of expanded molecular cytogenetic testing to pregnant women undergoing invasive prenatal diagnosis. This approach may be especially useful in parts of the world where cytogenetic personnel and facilities may be limited.

Early amniocentesis

Although amniocentesis was first reported in 1882, the technique was not in widespread clinical practice until the 1970's. The reason for this slow uptake was that there were few indications for performing the procedure until fetal karyotyping from amniotic fluid cells became possible in 1966. Currently fetal karyotyping is the commonest indication for the technique and amniocentesis has become the mainstay of antenatal diagnosis.

Overview of clinical cytogenetics

This unit provides an introduction to clinical cytogenetics. It opens with indications for prenatal and postnatal chromosome analysis, followed by a brief discussion of the applications of fluorescence in situ hybridization (FISH). It suggests tissue sources for prenatal and postnatal analysis, and closes with a review of numerical and structural chromosome abnormalities. This unit provides an introduction to clinical cytogenetics.

[Amniocentesis practice assessment of the south-west Francilian network during 2003]

OBJECTIVES

To assess amniocentesis practice of a network during one year.

MATERIALS AND METHODS

In a retrospective multicenter study of the south-west Francilian network, we have enrolled 2400 patients who underwent amniocentesis, from 1 January 2003 to 31 December 2003.

RESULTS

The rate of amniocentesis was 9.5%. The most frequent indication was a positive maternal serum screening test result (44%). The rate of global fetal losses (spontaneous miscarriage and intrauterine death) was 1.4%. Once the fetuses with aneuploidy and lethal pathology excluded, the rate of global fetal losses potentially related to amniocentesis was 1.21%. The rate of premature rupture of the membranes was 1.12% and prematurity affected 6.5% of the living births.

CONCLUSION

Our study has highlighted several practices of amniocentesis within the network. Overall, amniocentesis potentially induces 1.12% of fetal losses. Screening tests are currently used sequentially, which leads to an increase number of amniocentesis and to an increase number of losses of "a priori" healthy fetus. Only the use of a combined screening could lower the frequency of amniocentesis without decreasing the detection rate of chromosome abnormalities.

Quality aspects of prenatal cytogenetic diagnosis: determining the effect of various factors involved in handling amniotic fluid and chorionic villus material for cytogenetic diagnosis

OBJECTIVES

To investigate the effect of factors involved in cell culturing and slide preparation of amniotic fluid (AF) and chorionic villus biopsies (CVB) for prenatal cytogenetic diagnosis.

METHODS

The effect on the outcome of our standard AF cell culture procedure of volume and appearance of the submitted AF specimen, gynaecologist performing the amniocentesis, week of gestation in which the specimen was taken and culture medium was retrospectively investigated. In a prospective study controlled experimental variation was introduced in composition of fixative, relative humidity, temperature and airflow during slide preparation from primary CVB and AF in situ cultures. For evaluation, analysis of regression or variance was used.

RESULTS

Provided that at least 0.8 mL AF per culture dish was admitted, none of the investigated factors appeared as critical resulting in unacceptable variation in outcome. Variation in appearance of the AF had a relatively major impact: bloody or brown AF resulted in a 3 days longer culture time. To a limited degree, metaphase quality of AF and CVB cells was affected by composition of fixative, relative humidity, ambient temperature and airflow during slide preparation.

CONCLUSION

Current prenatal cytogenetic practice as described here appears in general to be robust and reliable. The investigated conditions are not critical within the investigated range. Expensive measures for fine control of these conditions are, therefore, not required.

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.

Diagnóstico pré-natal

O presente artigo apresenta uma descrição de todos os métodos de diagnóstico pré-natal de anormalidades genéticas e cromossômicas, bem como dos relativos a doenças infecciosas na gravidez. O autor discute as diferenças entre eles, e as novas ferramentas da biologia molecular que são aplicadas nesses diagnósticos. Ao final é feita uma descrição da técnica de diagnóstico pré-implantação e de seu uso in vitro em laboratórios de fertilidade situados a mais de dois mil quilômetros um do outro.

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.

First trimester prenatal diagnosis: amniocentesis

Twenty years after midtrimester genetic amniocentesis was first used, first trimester invasive prenatal procedures were introduced. Chorionic villous sampling presents some disadvantages that entitled many centers to look into an alternative for first trimester diagnosis. Early amniocentesis (EA) can be performed effectively, as shown over the years in many observational studies and partially randomized and randomized trials. Recently, a multicenter randomized trial (Canadian Early and Midtrimester Amniocentesis Trial) reported a higher total pregnancy loss, a significant increased incidence of musculoskeletal foot deformities, a significant increased culture failure rate, and an increased postamniocentesis rate of leakage in the EA group compared with midtrimester amniocentesis. These results concerning EA procedures from 11w(+0) to 12w(+6) should be included in any pre-EA counseling. However, further trials have started to evaluate EA procedures between 13w(+0) to 14w(+6).

Early pregnancy prenatal diagnostic testing: risks associated with chorionic villus sampling and early amniocentesis and screening options

Routine amniocentesis is an established test for the prenatal diagnosis of chromosome abnormalities and many single-gene conditions. Chorionic villus sampling and early amniocentesis, which are available in some centers, enable families to receive prenatal test results earlier in the pregnancy. There are concerns regarding the safety of early pregnancy testing because of increased risks for pregnancy loss and possible risks for birth defects. The use of first trimester testing has changed because of these concerns, and alternative methods of screening pregnancies at risk for a chromosome abnormality are being investigated.

Technical factors in early amniocentesis predict adverse outcome. Results of the Canadian Early (EA) versus Mid-trimester (MA) Amniocentesis Trial

The purpose of this study was to identify risk factors for fetal loss and other pregnancy complications associated with genetic amniocentesis. Data were acquired in the Canadian Early Amniocentesis Trial (CEMAT), a multicentered (12) prospective, randomized trial comparing continuous ultrasound-guided early amniocentesis (EA) and mid-trimester amniocentesis (MA) (CEMAT Group, 1998). Details of the procedure were recorded and analysed by allocation (EA versus MA), operator and centre, and correlated with pregnancy outcome. A total of 62 spontaneous pregnancy losses occurred between the procedure and 20 weeks' gestation among the 3691 patients who received their procedures within the allocated window (EA=53/1916, MA=9/1775). Technical factors correlating with these losses included procedures 'judged to be difficult' by the operator, and post-procedure amniotic fluid leakage or bleeding. Maternal risk factors included maternal hypertension (fetal loss 11. 1 per cent, compared with non-hypertensive women, 2.6 per cent) increased body mass index (BMI) and gravidity of three or greater. Allocation to EA was predictive of fetal loss, as well as failed procedure, multiple needle insertions, amniotic fluid leakage, failed culture and talipes equinovarus, in excess compared with MA. In conclusion, in this large prospective randomized trial evaluating amniocentesis, specific maternal, fetal and procedural variables were found to be predictive of fetal loss and adverse pregnancy outcome. Performing amniocentesis before 13 weeks' gestation (EA) was the major predictive factor for adverse outcome. These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype.

Amniotic fluid alpha-fetoprotein testing in native Japanese women

Owing to differences in maternal serum alpha-fetoprotein, human chorionic gonadotrophin and oestriol levels between native Japanese and Caucasian women screened in this laboratory, a study was conducted to measure amniotic fluid alpha-fetoprotein (AFAFP) levels in native Japanese pregnancies. When the native Japanese AFAFP levels were compared with a United States (non-Black) population, the Japanese medians did not decrease as rapidly over the 14 to 22 weeks of gestation period investigated. At 14 weeks, the difference was negligible, graduating to a difference of 20 per cent by 22 weeks' gestation. Native Japanese pregnancy AFAFP levels should be interpreted based upon population data from that group alone. From these findings, prenatal screening laboratories should be encouraged to collect preliminary data for comparison before screening is initiated for a defined ethnic group.

Cytogenetic aspects of the Canadian early and mid-trimester amniotic fluid trial (CEMAT)

Cytogenetic results from a large multicentre randomized controlled study of 2108 amniotic fluids obtained at 11+0-12+6 weeks (EA) and 1999 fluids at 15+0-16+6 weeks (MA) were compared. There was no statistically significant difference in the rate of chromosome abnormalities (EA =1.9 per cent; MA=1.7 per cent) or level III mosaicism (EA=0.2 per cent; MA= 0.2 per cent) between the groups. Level I and Level II mosaicism occurred more frequently in MA. Maternal cell contamination was not significantly different between the groups, but maternal cells only were analysed from one bloody EA fluid. The number of repeat amniocenteses because of cytogenetic problems was 2.2 per cent in the EA group compared with only 0.3 per cent in the MA group. On average, culture of EA fluids required one day more than MA fluids. Although both culture success (97.7 per cent) and accuracy (99.8 per cent) were high for patients randomized to the EA group, routine amniocentesis prior to 13 weeks' gestation is not recommended for clinical reasons including an increased risk of fetal loss and talipes equinovarus.

Comparison of cell cultures, chromosome quality and karyotypes obtained after chorionic villus sampling and early amniocentesis with filter technique

548 cell cultures and karyotypes obtained by early amniocentesis with filtration technique (EAF) at a mean gestational age of 12 1/2 weeks were compared with 555 obtained by transabdominal chorionic villus sampling (CVS) at a mean gestational age of 11 weeks. The number of abnormal karyotypes, culture failure rate and harvest time were evaluated. The results were then compared with three similar studies from the literature evaluating early amniotic fluid cultures obtained with conventional techniques compared with chorionic villus cultures. Further, the quality of the chromosome preparations from chorionic villi and early amniotic fluid respectively was compared. More abnormal karyotypes were found among the CVS cultures, which was expected due to earlier sampling and presence of confined placental mosaicism. No ambiguous results were present after EAF. The lowest culture failure rate of 0.2 per cent was found after EAF compared with 0.9 per cent among CVS. EAF also showed a significantly lower culture failure rate when compared with the literature, where early amniocentesis (EA) had been carried out by standard techniques. The time from sampling to harvest was longer in the EAF group (mean 9.5 days) compared with CVS (mean 6.1 days), in accordance with the literature. Nevertheless, the culture time of EAF was significantly shorter than the mean of EA from the comparative studies, whereas CVS culture times showed no differences. Rates of pseudomosaicism, maternal cell contamination, single cell aberrations, number of chromosome bands, mitoses counted and number of primary cultures needed for each karyotype were also compared. We concluded that EAF carried out around 12 1/2 weeks of gestation is a successful method with a lower culture failure rate compared with CVS cultures from 11-week gestations and with a significantly lower culture failure rate when compared with EA from similar studies. EAF provides chromosome preparations of high quality, and the risk of ambiguous karyotypes is very low.

Randomised study of risk of fetal loss related to early amniocentesis versus chorionic villus sampling

BACKGROUND

Several cohort studies have shown the feasibility of early amniocentesis (between 11 and 13 weeks of gestation) as an alternative to chorionic villus sampling (CVS) for karyotyping, but the only completed randomised study of fetal safety showed a significant fetal-loss risk related to first-trimester amniocentesis. We assessed fetal safety in early amniocentesis and CVS.

METHODS

We assessed early amniocentesis at 11-13 weeks gestational age compared with the fetal risk associated with CVS at 10-12 weeks. 1160 pregnant women were randomly assigned one procedure (581 early amniocentesis, 579 CVS) after a baseline ultrasound examination at 10 weeks' gestation and were followed up until birth. Total fetal loss and neonatal morbidity were the primary outcome measures. Sampling success and pregnancy complications were secondary outcomes. We used a filter to increase the cell yield in the early amniotic-fluid samples. CVS was transabdominal.

FINDINGS

We found a significantly increased occurrence of talipes equinovarus in the early amniocentesis group (p < 0.01), the risk of which was associated with sampling at the earliest gestational ages and with temporary leakage of amniotic fluid after sampling. Therefore, the trial was stopped early, which reduced the power of the safety study. 4.8% (27) of fetuses in the CVS group and 5.4% (30) in the early amniocentesis group were lost after randomisation (p = 0.66). More detailed survival analysis did not show any significant differences in fetal loss rates. Leakage of amniotic fluid after sampling occurred significantly more frequently after early amniocentesis than after CVS (p < 0.001), but we found no other major differences in pregnancy complications. Significantly more CVS than early amniocentesis procedures were repeated or failed to produce a karyotype (p < 0.01).

INTERPRETATION

Even though the numbers were small, we found an association between early amniocentesis and talipes equinovarus. We believe this association to be true, since it supports a trend in a similar randomised study. Our results show that early amniocentesis, when done with the filter technique, is associated with an abortion risk similar to CVS, although the limited size of our study population reduced the strength of this conclusion.

A prospective comparative study on transabdominal chorionic villus sampling and amniocentesis performed at 10-13 week's gestation

Women with single, viable pregnancies at 10 + 5 to 13 + 6 weeks, gestation who requested fetal karyotyping for maternal age, parental anxiety, or a previous history of chromosomal aberration were offered participation in this study. With a transabdominal ultrasound-guided technique, early amniocentesis (EA) was performed on 147 women and chorionic villus sampling (CVS) on 174. Spontaneous fetal loss occurred in 6.8 per cent in the EA group and 1.7 per cent in the CVS group. This difference was significant with a confidence interval (CI) of 0.6-9.6 per cent. There was also a significant difference in the need for repeat testing between the groups. In the EA group a repeat test was required in 19.0 per cent due to culture and sample failures, while 5.2 per cent of the women in the CVS group needed repeat testing because of ambiguous results. This prospective study comparing EA and CVS shows that the risk of fetal loss is higher and repeat testing is needed more after EA.

The moral aspects of prenatal diagnosis

The incidence of significant birth defects or genetic disorders in pregnancy is approximately 3%. Some will be found to have a congenital or genetic defect during childhood or early adulthood. The demands of modern society are for a healthy 'perfect' baby. Recent technological advances have enabled the development of techniques aimed at early diagnosis of the abnormal fetus, at a point where parents who wish to do so may terminate the pregnancy. Some of these techniques render the woman and fetus at risk of harm, whereas in others, efficacy has not yet been established. The implementation of these techniques raises several ethical questions which will be discussed in this article. We will also give a concise scientific background to the available techniques.

Early filtration amniocentesis for further investigation of mosaicism diagnosed by chorionic villus sampling

In 44 pregnancies where chorionic villus sampling (CVS) had shown mosaicism, early amniocentesis using a filter technique was carried out with the purpose of clarifying the fetal karyotype and reducing the waiting time for a final karyotype. Since the filter technique increases the cell yield of the amniotic fluid sample, it was hypothesized that this technique could be applied as soon as the mosaic CVS result was available, without compromising the culturing of the amniotic fluid cells. The mean gestational age at amniocentesis was 12.5 weeks and the mean gestational age at the time of the final karyotype was 13.9 weeks. All amniotic fluid sampling procedures and cultures were successful. Four pregnancies were terminated due to abnormal karyotypes (9.1 per cent). Two spontaneous abortions occurred in the second trimester (5.0 per cent), and one infant was lost at term due to unexplained intrapartum death. The total fetal loss rate was 7.5 per cent. This loss rate is concordant with other reported series where the outcome of pregnancies with placental mosaicism has been evaluated. We conclude that early amniocentesis with the filtration technique is a useful method for follow-up on CVS, mosaicism, providing results prior to 14 weeks of gestation.

Early amniocentesis at 10-12 weeks' gestation

In this study we report the results of 181 ultrasound-guided genetic amniocenteses performed at 10-12 weeks of gestation and describe the indication, technical problems, amniotic fluid volume, culture success and timing, abortion and fetal loss rate, and perinatal results. Amniotic fluid was obtained in 98.4 per cent of the cases; at the first attempt, in 167 out of 181. The culture success rate was 94.5 per cent, and the fetal loss rate within 2 weeks was 0.5 per cent (one case with a sonographic abnormality). The total fetal loss rate during pregnancy was 1.6 per cent. A comparison of our data and those of other published series shows no significant differences, either with respect to this period of gestation (10-12 weeks) or with respect to the traditionally called early amniocentesis' (12-14 weeks) or conventional amniocentesis (15 weeks or more). The mean culture time was just a few days longer in some of the series, and in some cases, there was also a lower success rate after culture, particularly when amniocentesis was carried out at 10 weeks or less. We conclude that amniocentesis performed at 10-12 weeks is feasible, safe, and easy to perform, and provides a real benefit to the pregnant woman.

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.

Early amniocentesis: a clinical review

Early amniocentesis at less than 14 weeks gestation is becoming more common in prenatal diagnosis populations. Randomized studies are minimal and have not had the power to determine the accuracy and safety of the procedure compared to chorionic villus sampling or mid-trimester amniocentesis. Procedures at 11+0-12+6 weeks should be considered experimental. This clinical review considers the ethics, embryology, and clinical experience (cytogenetics, AFP, AChE, procedure and cytogenetic failures, spontaneous and therapeutic pregnancy losses, congenital anomalies) of early amniocentesis.

The origin of alpha-fetoprotein in first-trimester anembryonic pregnancies

OBJECTIVE

Our purpose was to evaluate the origin of alpha-fetoprotein in the maternal circulation and coelomic fluid of pregnancies with an empty gestational sac on first-trimester ultrasonographic examination.

STUDY DESIGN

The alpha-fetoprotein level and the affinity of alpha-fetoprotein for concanavalin A Sepharose was measured between 8 and 11 weeks of gestation in the maternal serum and coelomic fluid of nine pregnancies complicated by an empty gestational sac and of 27 normal pregrancies.

RESULTS

The maternal serum alpha-fetoprotein level in patients with an empty gestational sac was high in seven cases and normal in two cases. In these cases the median level was significantly (p < 0.01) higher in the serum and lower in the coelomic fluid compared with normal pregnancies. In eight cases of the nine pregnancies with an empty sac, > 50% of alpha-fetoprotein molecules in the coelomic fluid were of the concanavalin A nonreactive fraction, whereas in one case the coelomic fluid sample contained < 5% of this fraction. A similar distribution was found in the corresponding serum samples.

CONCLUSION

Normal or high maternal serum AFP levels and alpha-fetoprotein molecules predominantly of yolk sac origin in the coelomic fluid of pregnancies with an empty gestational sac on ultrasonography provide further evidence that the most likely explanation for this feature is the early death of the embryo with persistence of the placental tissue.

Risk assessment of amniocentesis between 11 and 15 weeks: comparison to later amniocentesis controls

We studied 693 consecutive early amniocenteses (prior to 15 weeks) and found a spontaneous abortion rate to 28 weeks' gestation of 1.5 per cent. A control group of women having standard amniocentesis (15-20 weeks) experienced a 0.6 per cent fetal loss in the same period. There were no other apparent differences between the two groups. Early amniocentesis results are generally available 4-6 weeks before standard amniocentesis and 1-3 weeks after chorionic villus sampling (CVS). Alpha-fetoprotein (AFP) can be accurately assayed in 11- to 15-week amniotic fluid samples but additional studies are necessary to determine the accuracy of neural tube defect (NTD) detection. Including the present study, over 5800 early amniocenteses have been reported and the results suggest that this is a relatively safe prenatal diagnostic test and an alternative to CVS and later amniocentesis.

True trisomy 15 mosaicism, detected by amniocentesis at 12 weeks of gestation and fetal echocardiography

A case of mosaicism of trisomy 15, with two-thirds of the cells trisomic, was detected at 12 weeks of gestation in amniotic fluid cell cultures obtained with the filtration technique. Ultrasound examination at 13 weeks showed a nodule protruding into the amniotic cavity which was speculated to be remnants of a co-twin, causing the trisomic cell line. At 20 weeks of gestation, a malformation scan (level III) was normal, but supplementary fetal echocardiography revealed a severe cardiac defect (mitral atresia and a ventricular septal defect). Fetal lymphocytes obtained by cordocentesis showed trisomy 15 mosaicism, but only in 5 per cent of the mitoses. After termination, the same percentage of trisomy 15 mosaicism was found in cells from skin and tendon as in the original early amniocentesis. No sign of earlier twinning was found in the placenta or membranes. We conclude that mosaicism in early amniotic fluid obtained by the filter technique in this case reflected the true karyotype accurately and that supplementary echocardiography added significantly to the interpretation of the clinical implications.

Early amniocentesis--a cytogenetic evaluation of over 1500 cases

We report our cytogenetic experience of 1554 early amniocenteses between weeks 11 and 14 of gestation, of which 44 per cent were performed prior to week 14. The mean culture time was 14.5 days. Karyotyping was successful in 99.7 per cent of cases. In 9.9 per cent of cases, there was pseudomosaicism with a high rate of loss of an X-chromosome and structural aberration of chromosome 1, which may be due to the Chang medium. The mosaic rate was 0.5 per cent. The overall aberration rate was 2.8 per cent. Our data confirm the reliability of early amniocentesis, which is a serious alternative to standard amniocentesis and chorionic villus sampling (CVS).

Comparison of first-trimester transvaginal amniocentesis with chorionic villus sampling and mid-trimester amniocentesis

Between August 1989 and December 1991, 356 patients underwent first-trimester transvaginal amniocentesis (10-12 weeks). The same number of patients referred in the same period for mid-trimester amniocentesis (14-21 weeks) was matched also for maternal age and indication. A third group consisted of the first 356 cases in which chorionic villus sampling (CVS) was attempted. The overall success rate was 99.7 and 100 per cent for early and mid-trimester amniocentesis, respectively, and 97.2 per cent for CVS. The mean harvesting time was 12.8, 11, and 7.9 days, respectively. The percentage of patients rescheduled was 3.4 per cent in first-trimester amniocentesis, 1.7 per cent in mid-trimester amniocentesis, and 6.2 per cent in the CVS group. The early (less than 2 weeks) pregnancy loss was 1.7 and 0.6 per cent in early and mid-trimester amniocentesis, respectively, and 1.7 per cent in CVS. The total pregnancy loss was 3.2, 0.9, and 2.9 per cent, respectively. The rate of preterm birth was 6.0, 5.2 and 6.9 per cent, respectively. The results indicate that CVS has the shortest procedure-result interval, but the highest rescheduling rate. First-trimester amniocentesis has a higher procedure and laboratory success rate but, until otherwise proved, mid-trimester amniocentesis is the most efficient and safest procedure.

Filtration and recirculation of early amniotic fluid. Evaluation of cell cultures from 100 diagnostic cases

Due to the low cell concentration, cultures from early amniotic fluid specimens usually require 2-3 weeks in culture prior to karyotyping. The purpose of this study was to evaluate the culture quality of amniotic fluid cells from early pregnancy, obtained by a new filter technique. The hypothetical advantage of the technique was that the increased cell yield might reduce the culture time before karyotyping. Culture quality was assessed by the number of colonies, the percentage of colonies containing mitoses in filter and control cultures, and the culture time. The setting was a consecutive clinical trial. One hundred samples were obtained from ongoing pregnancies at 11-14 weeks of gestation (mean 12.8 weeks). By circulating a mean of 26 ml of amniotic fluid through a cell filter system leading the cell-free fluid back to the amniotic cavity, the cell yield was increased in the sample of 7 ml corresponding to the dead space of the filter system. The culture results were compared with control cultures from 5 ml samples drawn from the same pregnancies prior to recirculation. The cultures from the first flushing of the filter system yielded 2.6 times more colonies and in total 4.2 times more colonies were found in the three cultures grown from each filter sample when compared with the control cultures. Moreover, the filter cultures showed significantly more colonies with mitoses. The mean culture time was 8.0 days for the filter cultures, from which the karyotypes were analysed. The controls would have needed more time in culture to fulfil the diagnostic criteria for karyotyping. One case of 47,XY,+21 was found; the rest had normal karyotypes. We conclude that the filter technique improves the culture quality of early amniotic fluid samples and allows early arrest of the cultures.

Antenatal diagnosis of pediatric surgical anomalies. Counseling the family

Improvements in screening and diagnostic techniques now mean that hundreds of congenital anomalies can be antenatally diagnosed. It is, however, impossible and inappropriate to submit all pregnant women to a barrage of investigations. Screening is necessary before specific invasive investigations are initiated. These include history, physical examination, MS-AFP screening, estriol and hCG screening, and a Level II ultrasonography scan. Once at-risk pregnancies have been identified, a multidisciplinary team approach is commenced and further studies including Level II ultrasonography, amniocentesis, chorionic villus sampling, or cordocentesis can be performed so that an accurate diagnosis is available. Counseling of the parents throughout is essential so that appropriate decisions regarding this and further pregnancies can be made.

Testing for fetal abnormality in routine antenatal care

The detection of fetal abnormality is a major component of routine antenatal care. A variety of techniques are now in use, although these are constantly being modified in the pursuit of more accurate and earlier detection. In this paper we draw attention to the distinction between screening and diagnostic tests, and describe the techniques which have been most commonly used in the UK: serum-screening for neural tube defects; screening for Down's syndrome; ultrasound scanning; amniocentesis and chorionic villus sampling.

Cytogenetic analysis of 1375 amniotic fluid specimens from pregnancies with gestational age less than 14 weeks

Our laboratory has received 1375 early amniotic fluid (EA) specimens during the past 5-year period for cytogenetics analysis. The gestational ages of the EA specimens were less than 14 weeks as estimated by ultrasound. The average volume of specimen received was 16 ml. Specimens were typically received in two collection tubes and cultured in Chang A and in supplemented MEM media using the in situ technique. Of the 1375 EA specimens received, 1356 were successfully cultured and yielded results. Abnormal results were found in 67 (4.9 per cent) of the cases. Nineteen specimens (1.4 per cent) failed to yield a result. The mean turn-around time (TAT) for all EA specimens was 8.28 days. In 1991, the average TAT for the EA specimens was 8.00 days compared with a TAT of 6.59 days for all specimens received over 14 weeks gestational age. The number of EA specimens received has increased from 1.5 per month in 1986 to 57 per month in 1991. In summary, our experience with EA specimens for cytogenetic analysis has demonstrated that the success rate is 98.6 per cent and that an increasing number of obstetricians are performing early amniocentesis as they seek to provide their patients with earlier results and an alternative to chorionic villus sampling.

Cytogenetic analysis of 2928 CVS samples and 1075 amniocenteses from randomized studies

We report cytogenetic results from a randomized Danish chorionic villus sampling (CVS) and amniocentesis (AC) study including 2928 placental and 1075 amniotic fluid specimens processed in the same laboratory. The results are presented in groups comparing CVS with amniocentesis and transabdominal (TA) CVS with transcervical (TC) CVS as randomized. More abnormalities and more ambiguous diagnostic problems were found in placental tissues than in amniotic cells. There were no diagnostic errors and no incorrect sex predictions. Mosaicism was detected in 1 per cent of all cases of CVS (discordancies included). When confirmation studies were done, 90 per cent were found to be confined to the placenta. Eight cases (0.7 per cent) of mosaicism/pseudomosaicism were seen in amniotic fluid specimens, and two cases of five with confirmation studies were confirmed in the fetus. The rate of mosaicism/pseudomosaicism in CVS and AC specimens differed (p < 0.05). The rate of pseudomosaicism in cultures of villi and amniotic fluid cells was 0.5 and 0.6 per cent, respectively. Single-cell aneuploidy was observed in 1.8 per cent of villi and 1.4 per cent of amniotic fluid cell specimens. Maternal cell contamination (MCC) was seen more often after TC sampling (4.5 per cent) compared with TA sampling (1.5 per cent), but posed no problems in interpretation. Compared with the processing of cultured specimens, the short-term method of preparation of villi in our laboratory doubled the technicians' workload. For practical and economic reasons we have ceased the routine use of short-term preparations.

Evaluation of amniotic fluid cell filtration: an experimental approach to early amniocentesis

Prior to a prospective application of amniotic fluid (AF) cell filtration to early amniocentesis, we tested the technique on a surplus from mid-trimester samples. By using the same sample size of 5 ml in experiments with a filter and in routine diagnostic procedures (control), we evaluated an optimal filter system. The prolonged culture time of filtered cells and the reduced number of clones are most probably due to mechanical stress (filtration pressure), whereas loss of the cells by adhesion to the filter system, and an AF-free culture medium (growth factors) are suggested to be less important. The AF cells are very sensitive to mechanical stress. Slow filtration (< or = ml AF/min) through filters with a high porosity and the largest possible pore size should be preferred. A mixed cellulose ester filter membrane with a pore size of 5.0 microns proved to be the most efficient, allowing harvest of the filtered cells after only a slight prolongation of the culture time (+2.4 days) compared with unfiltered aliquots. A filter set with a bypass connected by three-way taps allows cell filtration during either aspiration or reinjection of the AF. Cell filtration after amniocentesis and consecutive reverse flushing of the membrane with the appropriate amount of culture medium proved to be the best with regard to easy handling and reducing the risk of bacterial contamination.

Early genetic amniocentesis--4 years' experience

Four hundred and thirty early amniocenteses (EAC) from 10 to 14 weeks' gestation were compared with 300 routine amniocenteses (RAC) from 15 weeks' gestation (control A) and 733 routine amniocenteses from 16 to 18 weeks' gestation (control B) with regard to success rates, various growth parameters, and cytogenetic results. Using both in situ and trypsinization techniques, the success rate was 99.8 per cent for EAC versus 100 per cent for RAC. The average turn-around time for establishing a diagnosis was 8.4 days in EAC versus 8.3 days in 15 weeks' specimens (n.s.) and 7.7 days in 16 to 18 weeks' specimens (p < 0.0001) for the last 200 samples. The banding quality of early specimens compared favourably with that of controls (both 500-550 bphs) and was much better than that in long-term cultured chorionic villus sampling (CVS) (350-400 bphs). For level I and level II mosaicism, no statistically significant differences were noted between EAC and control group A. Comparing EAC with control group B, a significant increase in the number of numerical and structural single cell aberrations was observed (p < 0.025 and p << 0.001, respectively), whereas for multiple cell aberrations only the increase in numerical aberrations was statistically significant (p << 0.001) (chi 2-test). Clinical problems arising from the detection of mosaicism were solved in all cases by investigating parallel cultures. It is concluded that early amniocentesis is a reliable procedure which permits prenatal diagnosis of numerical and structural chromosome aberrations to a high standard.

Introduction of early amniocentesis to routine prenatal diagnosis

With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria 'number of colonies' and 'culture duration until harvest', early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis.

First trimester amniocentesis between the seventh and 13th weeks: evaluation of the earliest possible genetic diagnosis

Amniocentesis performed at the 12th week and later gives reliable results. The procedure can be performed using regimens developed for mid-trimester amniotic fluid (AF) cells. Extension to the 10th-11th week is, in principle, feasible. However, the high cytogenetic failure rate is a difficulty and despite a high clone count, the culture time is prolonged. The problem of the relatively high loss of AF could be overcome by cell filtration techniques and replacement of the fluid. Because of the short turnover rate of the AF, this may be unnecessary or replacement with an isotonic solution may be sufficient. (Pseudo)mosaicism appears to occur more frequently in early than in late amniocentesis. As yet, data are too sparse to allow a comparison with chorionic villus sampling. There are no reliable follow-up data from which to estimate the abortion rate and the number of embryonic malformations.

Diagnosis of abnormalities of the human fetus during the first, second, and third trimesters

Clinical teratologists will have new challenges during the 1990s as birth defects are diagnosed more frequently than in previous decades. Malformations and genetic disorders will be diagnosed in utero during all three trimesters of pregnancy. The teratologist may participate in or lead a multispecialty group to give the involved family optimal interpretation of test results, counseling, and recommendations regarding subsequent clinical management.

Early amniocentesis: outcome, risks, and technical problems at less than or equal to 12.8 weeks

OBJECTIVE

It is the purpose of this report to evaluate our experience with amniocentesis at less than or equal to 12 weeks' gestation.

STUDY DESIGN

Medical records of 936 patients at less than or equal to 12.8 weeks' gestation undergoing genetic amniocentesis between Oct. 1, 1986, and June 30, 1990, were evaluated for gestational age, indication, frequency of needle insertion, amniocentesis complications, and pregnancy outcome.

RESULTS

There were seven miscarriages within 2 weeks of amniocentesis (0.7%), 21 miscarriages before 28 weeks (2.2%), and four stillbirths or neonatal deaths (0.4%), resulting in a total postprocedural loss rate of 3.4%. There were 26 chromosomally abnormal fetuses (2.8%). The spontaneous abortion rate in ultrasonographically normal pregnancies at less than 14 weeks, not undergoing amniocentesis, has been estimated at 2.1% to 3.2%.

CONCLUSION

Amniocentesis at 12 weeks is a viable option for patients desiring earlier prenatal genetic diagnostic information.