Demographic Studies from a National Gaucher Disease Screening Program

In May 1993, the National Gaucher Foundation initiated a nationwide Gaucher disease screening program in an attempt to promote recognition of the disease and to detect previously undiagnosed individuals. The program was based on self-selection by clinical symptoms of individuals who wanted to be tested for Gaucher disease. Information about symptoms, age, ancestry, gender, and family history was obtained via a self-report screening form completed by 700 individuals. Individuals designated at "high risk" for Gaucher disease were offered beta-glucocerebrosidase enzyme assay testing. Twenty-four of the respondents (3.4%) had Gaucher disease. The most commonly reported symptoms were fatigue (79.4%), bone pain (73.7%), and tendency to bruise (67.8%). The symptoms which showed a statistical difference between the "high risk" and "low risk" groups were liver enlargement (p < 0.005) and unexplained bone fractures (p < 0.03). The mean number of positive symptoms also showed a statistical difference between the groups (4.38 symptoms vs. 3.86 symptoms; p < 0.02). Due to the small sample size, no statistical comparisons were made on the symptomatology of affected vs. unaffected persons, but a descriptive analysis of these two groups is reported.

Non-invasive prenatal testing for aneuploidy: current status and future prospects

Non-invasive prenatal testing (NIPT) for aneuploidy using cell-free DNA in maternal plasma is revolutionizing prenatal screening and diagnosis. We review NIPT in the context of established screening and invasive technologies, the range of cytogenetic abnormalities detectable, cost, counseling and ethical issues. Current NIPT approaches involve whole-genome sequencing, targeted sequencing and assessment of single nucleotide polymorphism (SNP) differences between mother and fetus. Clinical trials have demonstrated the efficacy of NIPT for Down and Edwards syndromes, and possibly Patau syndrome, in high-risk women. Universal NIPT is not cost-effective, but using NIPT contingently in women found at moderate or high risk by conventional screening is cost-effective. Positive NIPT results must be confirmed using invasive techniques. Established screening, fetal ultrasound and invasive procedures with microarray testing allow the detection of a broad range of additional abnormalities not yet detectable by NIPT. NIPT approaches that take advantage of SNP information potentially allow the identification of parent of origin for imbalances, triploidy, uniparental disomy and consanguinity, and separate evaluation of dizygotic twins. Fetal fraction enrichment, improved sequencing and selected analysis of the most informative sequences should result in tests for additional chromosomal abnormalities. Providing adequate prenatal counseling poses a substantial challenge given the broad range of prenatal testing options now available.

Discordance among blastomeres renders preimplantation genetic diagnosis for aneuploidy ineffective

PURPOSE

To investigate the contribution of discordance among blastomeres from the same embryo in the interpretation of blastomeres biopsied from day 3 embryos.

METHODS

228 IVF embryos had two blastomeres removed and fluorescent in situ hybridization (FISH) was used to detect aneuploidy of chromosomes 13, 15, 16, 18, 21, 22, X and Y. Of the 228 embryos, 102 had complete FISH results for both blastomeres.

RESULTS

When the 2 blastomeres of 102 embryos with successful FISH results were compared, 26 (25.5%) were concordant for all 8 chromosomes and 76 (74.5%) were discordant for one or more chromosomes. Among the 102 embryos, 12 (12%) were disomy in both blastomeres and 37 (36%) were disomic in all 8 chromosomes in one of the two blastomeres.

CONCLUSION

Discordance among blastomeres from the same embryo appears to present a significant problem in interpreting results of embryos biopsied on day 3 and analyzed by FISH especially when most PGD's are done on single blastomeres.

Late first-trimester invasive prenatal diagnosis: results of an international randomized trial

OBJECTIVE

To assess, in a randomized trial, the safety and accuracy of amniocentesis and transabdominal chorionic villus sampling (CVS) performed at 11-14 weeks of gestation, given that this time frame is increasingly relevant to early trisomy screening.

METHODS

We compared amniocentesis with CVS from 77 to 104 days of gestation in a randomized trial in a predominantly advanced maternal age population. Before randomization, the feasibility of both procedures was confirmed by ultrasonography, and experienced operators performed sampling under ultrasound guidance; conventional cytogenetic analysis was employed. The primary outcome measure was a composite of fetal loss plus preterm delivery before 28 weeks of gestation in cytogenetically normal pregnancies.

RESULTS

We randomized 3,775 women into 2 groups (1,914 to CVS; 1,861 to amniocentesis), which were comparable at baseline. More than 99.6% had the assigned procedure, and 99.9% were followed through delivery. In contrast to previous thinking, in the cytogenetically normal cohort (n = 3,698), no difference in primary study outcome was observed: 2.1% (95% confidence interval 1.5, 2.8) for CVS and 2.3% (95% confidence interval, 1.7, 3.1) for amniocentesis. However, spontaneous losses before 20 weeks and procedure-related, indicated terminations combined were increased in the amniocentesis group (P =.07, relative risk 1.74). We found a 4-fold increase in the rate of talipes equinovarus after amniocentesis (P =.02) overall and in week 13 (P =.03, relative risk = 4.65), but data were insufficient to determine this risk in week 14.

CONCLUSION

Amniocentesis at 13 weeks carries a significantly increased risk of talipes equinovarus compared with CVS and also suggests an increase in early, unintended pregnancy loss.

LEVEL OF EVIDENCE

I

Preference assessment of prenatal diagnosis for Down syndrome: is 35 years a rational cutoff?

OBJECTIVE

To compare the perceptions of miscarriage and birth of a child with Down syndrome among pregnant women and to evaluate the implications of these preferences for the traditional 35-year old maternal age risk boundary.

METHODS

An interviewer-administered survey was given to 186 pregnant women receiving antepartum care at a university hospital. Preferences, as reflected by utilities, for birth of a child with Down syndrome and pregnancy miscarriage, stratified by patient characteristics, were assessed.

RESULTS

The utility for the birth of a child with Down syndrome decreased (p < 0.001) as clinical severity increased from mild (0.78) to severe (0.65). Miscarriage of a pregnancy had a mean utility of 0.76 +/- 0.31. Women who desired prenatal diagnosis had a utility value for miscarriage (0.79 +/- 0.28) that was significantly higher than for the birth of a child with Down syndrome of unknown severity (0.73 +/- 0.27). In multivariable logistic regression, desire for prenatal diagnosis was the only factor associated with a preference of miscarriage over birth of an affected child (odds ratio 2.26, 95% confidence interval 1.03, 4.96).

CONCLUSION

Women who desire prenatal diagnosis do not perceive the birth of a child with Down syndrome and a pregnancy miscarriage to be equivalent health states. This finding calls into question the rationale of the 35-year-old maternal age criterion and suggests that actual patient preferences should be better incorporated into the decision to offer definitive prenatal diagnosis.

Assessment of fetal status in multiple gestation pregnancies using interphase FISH

The use of fluorescence in situ hybridization (FISH) for women with multiple gestation pregnancies has been evaluated. Women were referred for chromosome analysis because of advanced maternal age, abnormal ultrasound findings or a positive family history and/or prior to fetal reduction. FISH was successfully applied to all specimens obtained by amniocentesis or chorionic villus sampling (CVS). Based on FISH results, fetal-fetal contamination of specimens following CVS was 11.5% in twin pregnancies and 16% in triplet or higher multiples. FISH detected trisomy 21 in three cases with no false negatives or positives. Whereas FISH may provide rapid and useful assessment of fetal status in decision-making regarding fetal reduction, the present study also highlighted the obstetrical difficulty of ensuring a sample representative of each fetus following CVS in addition to the possibility of not identifying clinically significant chromosome aberrations using currently available FISH probes.

New molecular techniques for chromosome analysis

The advent of molecular genetic technology has significantly advanced knowledge about the structure of chromosomes and their behaviour during meiosis and mitosis, as well as delineating cytogenetic aberrations that cannot be identified by conventional chromosome analysis. Molecular cytogenetics, the visualization of genetic loci using the dynamic recombinant technology of fluorescence in situ hybridization (FISH), now provides the obstetrician and gynaecologist with increasingly important diagnostic and prognostic information heretofore unavailable. The technical principles underlying FISH are briefly discussed. Emphasis is placed on the clinical applications of FISH and technologies derived from FISH, in particular comparative genome hybridization, microdissection FISH and multiplex FISH. These technologies play increasingly significant roles in preimplantation and prenatal genetic diagnosis, in the identification of microdeletion syndromes, cryptic translocations and marker chromosomes, and in defining chromosome mosaicism. FISH and related technologies also constitute essential diagnostic modalities in follow-up of organ transplantation, in a variety of haematological disorders and in determining the amplification of oncogenes associated with specific forms of cancer and neoplasia.

Recurrent triploidy of maternal origin

We report the occurrence of triploid preimplantation embryos following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in a woman with two previously-identified triploid conceptuses which spontaneously underwent fetal demise at 10 and 23 weeks' gestation. An error in maternal meiosis II is proposed as the most likely cause.

The application of fluorescence in-situ hybridization to prenatal diagnosis

Fluorescence in-situ hybridization has become essential in prenatal diagnosis for identifying chromosome aberrations as well as in preimplantation genetic diagnosis and the analysis of fetal cells in maternal blood. Comparative genome hybridization, multicolor fluorescence in-situ hybridization and telomere probes provide technical approaches for the characterization of fetal chromosome anomalies not possible by conventional karyotyping.

The clinical application of interphase FISH in prenatal diagnosis

Fluorescence in situ hybridization (FISH) for five chromosomes (13, 18, 21, X and Y) detected 87 of 107 (81%) of the chromosome aberrations identified by conventional chromosome analysis applied to fetal interphase cells obtained by chorionic villus sampling or amniocentesis. The choice of FISH was solely determined by prospective parents after formal genetic counselling concerning the advantages and disadvantages of FISH analysis. Excluding known familial chromosome aberrations, if FISH analysis revealed normal signals, there was an overall residual risk of 1 in 149 for an undetectable chromosome aberration. This risk varied according to the indication for prenatal diagnosis: 1 in 177 for women of advanced maternal age; 1 in 60 for women at increased risk for Down syndrome based on maternal serum screening; and, 1 in 43 for women whose ultrasound examination revealed fetal anomalies. There were 20 cases of discordance between the FISH results and standard karyotype analysis: four were the outcome of a failure to apply the appropriate FISH probe; 16 were not detectable by the available FISH probes. Of these 16, nine were chromosome abnormalities with clinical significance and seven were familial. If FISH is to become a standard part of prenatal genetic diagnosis, genetic counselling that is sensitive to patient health needs must be based on accurate information about the biological and obstetrical implications of the results of FISH analysis.

The role of the preimplantation geneticist in human cloning

If human cloning is to become a reality, the preimplantation geneticist must be responsible for determining the indications for undertaking cloning and for establishing the risks and benefits of human cloning. The unresolved issue is whether a compelling argument can be made for cloning a human for therapeutic reasons while outweighing legal, moral and ethical objections. At present, 'whole person' cloning does not seem justified under any circumstance, whereas cloning for the replacement of diseased cells, tissues or organ systems, i.e. 'spare parts', seems to be a likely, acceptable application of cloning strategies for humans.

At the crossroads: the intersection of the Internet and clinical oncology

The Internet is rapidly becoming a third party in the doctor-patient relationship. The World Wide Web, electronic mail (e-mail), and discussion groups have dramatically increased the quantity of medical and health information available to patients, who, in turn, vary greatly in their understanding of that newly discovered information. This article reviews the advantages and disadvantages of the Internet for both oncology patients and physicians. This forms the background for a discussion of three steps that clinical oncologists and other health care professionals can take to direct and control the potential of the Internet so as to optimize patient care. These steps include: (1) finding out what type of cancer information is being disseminated on the Web; (2) using Internet-derived material that patients bring to the clinic as a stepping-stone for patient education; and (3) becoming an active participant on the Web. Each of these strategies requires health professionals to be proactive. The appropriate and effective use of the Internet, as well as its boundaries, are rapidly expanding in medicine and are likely to co-evolve with changes in patient-health care provider relationships.

The expression of genes in human preimplantation embryos

The study of gene expression in human preimplantation embryos is establishing itself as a necessary dimension of developmental biology and medical genetics. Transcripts identified in human preimplantation embryos include housekeeping genes, transcription and growth factor genes, sex-determining genes, tissue-specific genes and novel genes, as well as genes of unknown function. Strategies are being developed which will eventually permit the most sophisticated gene expression studies on single human embryos of co-ordinated transcription and translational regulation. There is both a need for international co-operation for the systematic construction of expression maps and a need to establish databases of expression patterns during different stages of human development. Understanding how genes are regulated in humans is essential for understanding both normal development and disease. Until recently, studies of gene expression and regulation during embryogenesis were almost exclusively limited to prokaryotes and to eukaryotes other than man. The introduction of artificial reproductive technologies in conjunction with the development of recombinant molecular technologies applicable to single cells has made possible the study of human development at its earliest stages (Pergament and Bonnicksen, 1994). Although there are still enormous technical challenges, robust strategies have been, and continue to be, developed for connecting DNA sequence to such endophenotypes as timing and level of genes expression at the single cell level. Questions currently being asked in human developmental genetic studies concern the pronucleus, the zygote and the preimplantation embryo: what genes are expressed? When are they expressed? What functions do they perform and how, in sequence or in combination? And, what elements control and regulate their expression? This review provides an overview of current knowledge about the expression of different embryonic genes during early human development and discusses future prospects, which includes a need for international co-operation similar to the Human Genome Project.

Factors associated with maternal cell contamination in amniocentesis samples as evaluated by fluorescent in situ hybridization

OBJECTIVE

To determine which patient- and procedure-related factors contribute to maternal cell contamination in uncultured amniocentesis fluid.

METHODS

One hundred thirty amniotic fluid (AF) samples were obtained by three operator groups: maternal-fetal medicine faculty (n=50), general obstetrician gynecologists (n=50), and obstetrics and gynecology residents supervised by maternal-fetal medicine faculty (n=30). These groups were designated "most," "intermediate," and "least experience," respectively. Study variables were recorded at the time of the procedure. Amniotic fluid cells from male fetuses underwent fluorescent in situ hybridization. Maternal cell contamination was calculated by analyzing 100 cells and determining the number of XX and XY cells. A control system was created to validate the methods used for AF processing and cell counting.

RESULTS

Median maternal cell contamination was 2.0%. Maternal cell contamination did not vary with body mass index (r=-.13, P=.14), gestational age (r=.08, P=.35), or placental location (P=.55). Maternal cell contamination was significantly elevated with placental penetration (6.0% compared with 1.0%, P < .001), two passes (27.5% compared with 2.0%, P=.002), blood-tinged fluid color (14.0% compared with 2.0%, P < .001), and operator inexperience ("intermediate experience" compared with "most experience," 4.5% compared with 1.0%, P=.026). Maternal cell contamination did not differ between the "most experience" and "least experience" groups (1.0% compared with 2.0%, not significant). Concordance between detected and actual maternal cell contamination in the control system was extremely high (concordance coefficient=0.98, P=.008), confirming the validity of the techniques used.

CONCLUSION

Our techniques of cell counting and maternal cell contamination calculation are accurate. Maternal cell contamination is increased with placental penetration, two passes, and operator inexperience. However, with expert supervision, inexperienced physicians can perform amniocentesis without an increase in maternal cell contamination.

Hybridization of chromosome 18 alpha-satellite DNA probe to chromosome 22

Fluorescence in situ hybridization (FISH) of uncultured chorionic villus diploid cells with a chromosome 18 alpha-satellite DNA probe (D18Z1) revealed a third small signal in addition to two large signals. FISH analysis of diploid metaphase cells from cultured chorionic villus cells and from maternal lymphocytes revealed that the third signal resulted from hybridization to the centromere of chromosome 22. This is the first report of a variant involving D18Z1 detected by FISH and of hybridization of alpha-satellite from a sub-metacentric chromosome to the centromere of an acrocentric chromosome. We propose that this inherited variant resulted from insertion of chromosome 18 specific alpha-satellite DNA sequences into the centromeric region of chromosome 22.

Insulin receptor substrate-1 is expressed at high levels in all cells of the peri-implantation mouse embryo

Insulin and insulinlike growth factors are important for embryonic growth and metabolism. Intracellular transduction for these factors has not been studied in the preimplantation mouse embryo. Peri-implantation mouse embryos synthesize insulinlike growth factor (IGF)-II ligand, insulin receptor, IGF-I receptor, and IGF-II receptor and respond to IGF-II, IGF-I, and insulin metabolically and mitogenically. Maternal tissues in the oviduct and uterus are also sources of IGF-I and insulin. Signaling of IGFs occurs through insulin receptor substrate (IRS)-1 and IRS-2. This paper shows that IRS-1 mRNA and protein are highly expressed in preimplantation mouse embryos, in embryonic cell lines, and in cultured blastocyst outgrowths. IRS-1 mRNA and protein are detected in embryo-derived cell lines cultured to produce the three cell lineages (stem cells, endoderm, and trophoblast cells). IRS-1 mRNA is detected by reverse transcription-polymerase chain reaction (RT-PCR) in the E3.5 blastocyst before implantation and in F9 teratocarcinoma stem cells and parietal endoderm cells. IRS-1 mRNA is detected by Northern blot hybridization at high levels in stem cells and in differentiated progeny of F9 cells and C3H/NE trophectoderm cells. IRS-1 protein was detected in these cell lines and in an overexpressing CHO-IRS-1 fibroblast cell line by immunocytochemistry. Cultured blastocyst outgrowths are a model for implantation events of the trophoblast/placenta lineage and endoderm/yolk sac lineage. In the blastocyst outgrowth, IRS-1 protein is detected in inner cell mass cells (ICM cells), primitive endoderm, parietal endoderm, and trophectoderm cells. These data suggest that IRS-1 is expressed in all cell lineages of the peri-implantation mouse embryo and mediates some effects of insulin and IGFs at this stage.

Urorectal septal defects in a female and her offspring

We report on a patient with an ectopic urethra opening into a septate vagina which was distended with urine. The anus and rectum were normal but separated from the urogenital sinus by a thin septum. After surgical repair the patient did well with the exception of recurrent urinary tract infections. At 16 years, she delivered a healthy boy by Cesarean section but miscarried a subsequent pregnancy 3 years later. The 12-13 week female fetus lacked a urethra and had an atretic vagina and cloacal anomalies consistent with a urorectal septum developmental defect. This report provides evidence that cloacal anomalies resulting from the improper development of the urorectal septum may have a genetic cause. Furthermore, we support the proposition previously set forth by Allen and Husmann [J Urol 145:1034-1039, 1991] that such anomalies be referred to as urorectal septal defects rather than cloacal anomaly variants. This terminology accurately represents the developmental defect and clearly distinguishes them from cloacal exstrophies, which are due to the abnormal development of the cloacal membrane and the subumbilical ventral abdominal wall.

Isolated hypoplastic left heart syndrome in three siblings

BACKGROUND

Reports of recurrent isolated hypoplastic left heart syndrome have been infrequent, and the genetic basis of this occurrence is not well understood.

CASE

A 32-year-old woman with a noncontributory medical and family history terminated her first pregnancy after the fetus was diagnosed with hypoplastic left heart syndrome. Chromosomes were normal and no extracardiac anomalies were found at autopsy. In one subsequent pregnancy, a healthy live-born neonate was delivered, but in two other pregnancies isolated hypoplastic left heart syndrome was diagnosed again.

CONCLUSION

Parents with an infant affected with hypoplastic left heart syndrome have been quoted a recurrence risk of 2%. The occurrence of isolated hypoplastic left heart syndrome in three siblings suggests that this anomaly has an autosomal recessive mode of inheritance. Consequently, the possibility of a recurrence risk higher than 2% should be included during counseling.

Isolated fetal pyelectasis: assessment of risk for postnatal uropathy and Down syndrome

Eight-two consecutive fetuses with ultrasound evidence of isolated pyelectasis (defined as dilation in the antero-posterior renal pelvic dimension of > or = 4 mm) were prospectively followed to determine the risk of postnatal uropathy and Down syndrome. In 98 (60%) kidneys, isolated pyelectasis was shown to be the first manifestation of a pathophysiological process that evolved into a gamut of postnatal uropathies (defined as urological conditions requiring remedial surgery or extended medical surveillance). Data quantifying the risk for postnatal uropathy in fetuses with varying degrees of isolated pyelectasis, at different gestational ages, are presented in figure format to facilitate prenatal counselling. Bivariate analysis showed that the evolution of isolated pyelectasis to uropathy was statistically significant when in utero progression was noted or in conjunction with other findings including contralateral pyelectasis (p < 0.01), male gender (p < 0.01) and increased kidney length (p < 0.001). Importantly, 55% of the infants requiring corrective surgery demonstrated in utero progression of pyelectasis (p < 0.002). Serial ultrasound examinations were necessary to evaluate progression or regression in the extent of pyelectasis. Finally, isolated pyelectasis was associated with an increase risk for Down syndrome, beginning at maternal age of 31 years, in the interval of 16-20 week's gestation.

Current practices of commercial cryobanks in screening prospective donors for genetic disease and reproductive risk

OBJECTIVE

To determine how the screening practices of commercial semen banks vary from published guidelines, which factors influence cryobanks to exclude prospective semen donors for genetic reasons, and the current role of clinical geneticists/genetic counselors in evaluating prospective semen donors.

DESIGN

The genetic screening of prospective donors by commercial semen banks was evaluated using written questionnaires completed by bank directors. Responses were analyzed to determine exclusion criteria, adherence to published guidelines, and contribution of genetic professionals.

SETTING AND PARTICIPANTS

Semen banks were selected on the basis of membership in the American Association of Tissue Banks and commercial use of semen for artificial insemination by donor.

MAIN OUTCOME MEASURE

Semen bank practices as reported by commercial semen bank directors.

RESULTS

Of 37 eligible banks, 16 responded. All screen prospective donors by medical/family history and physical examination, 94% have upper age limits; 63% examine for minor physical defects; 56% routinely karyotype; 81% screen men of ethnic groups at risk for Tay Sachs disease, sickle cell disease and thalassemia; 19% screen all donors; 25% screen all donors for cystic fibrosis and 50% only screen if family history positive. Donor rejection was based on three criteria: mode of inheritance of familial disorder, severity of disease, and availability of carrier/confirmatory testing of donor genotype. Ten of 16 banks have no genetic professional on staff.

CONCLUSION

Commercial semen banks primarily rely on family history as the major exclusion criterion in genetic screening of donors. Considerable differences exist among semen bank practices in accordance with guidelines published by national agencies. Genetic professionals have a minimal effect overall on evaluation of semen donors.

Isolated hyperechoic fetal bowel: significance and implications for management

OBJECTIVE

The objective of this study was to determine the significance of isolated hyperechoic fetal bowel.

STUDY DESIGN

Forty-five cases with prospective, ultrasonographic diagnosis of isolated hyperechoic fetal bowel were reviewed. Fetal variables, including aneuploidy, deoxyribonucleic acid studies for cystic fibrosis, congenital infection, growth retardation, and intrauterine death were reported.

RESULTS

Thirty-four of the 45 cases (76%) resulted in live-born infants without detected abnormalities. However, hyperechoic bowel was associated with cystic fibrosis in two cases (4%), congenital infection in two cases (4%), and fetal alcohol syndrome in one case. Termination of pregnancy was elected in three cases and intrauterine fetal death occurred in three cases (7%). Growth retardation was observed in five of 39 (13%) live-born infants.

CONCLUSION

Isolated hyperechoic fetal bowel is associated with significant pathologic disorders. Women whose fetuses are diagnosed as having isolated hyperechoic bowel should be offered additional prenatal diagnostic options, including maternal serologic studies for congenital infection, fetal karyotype, and deoxyribonucleic acid testing for cystic fibrosis. In addition, continuing ultrasonographic evaluation of fetal growth and antenatal biophysical assessment should be considered.

Expression of transcription regulating genes in human preimplantation embryos

Utilizing a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay system, the time course of mRNA expression of two transcription regulators, OCT4 and OCT6, was assessed in individual preimplantation human embryos. Examination of ova with three pronuclei and 1-cell through blastocyst stage embryos revealed that OCT4 mRNA was continuously expressed between the time of fertilization and 10+ cell stages, whereas OCT6 mRNA expression was not observed until the 10+ cell stage. The difference in the time of expression of OCT4 mRNA and OCT6 mRNA indicates that the two genes play differential roles in human embryogenesis. Nucleotide sequence homology for OCT4 and OCT6 among mammalian organisms supports the concept that genetic elements determining developmental events during embryogenesis are conserved in evolution.

Adverse pregnancy outcome after a false-positive screen for Down syndrome using multiple markers

OBJECTIVE

To assess the relative risk of an adverse pregnancy outcome in women whose multiple-marker screening (maternal serum alpha-fetoprotein [MSAFP], unconjugated estriol [E3], and hCG levels, and age) indicating an increased risk for Down syndrome (more than 1:250) was not confirmed by amniocentesis.

METHODS

Fifty-eight women with false-positive screens for Down syndrome were matched with a control group of 116 women whose screens indicated a risk for Down syndrome of less than 1:250. The risk for adverse pregnancy outcome was compared for the two groups, and the roles of MSAFP, unconjugated E3, and hCG as predictors of adverse pregnancy outcome were determined.

RESULTS

Women with false-positive screens for Down syndrome were significantly different from their matched controls in the incidence of preterm delivery (20.6 versus 8.6%, respectively), preeclampsia (6.9 versus 0%), small for gestational age newborns (5.2 versus 0%), and fetal demise after 20 weeks' gestation (5.2 versus 0%). An adverse outcome occurred in 19 of 58 pregnancies (32.8%) in the study group and in 14 of 116 matched control pregnancies (12%) (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.6-7.8; P < .01). Unconjugated E3 of 0.75 multiples of the mean (MoM) or less was significantly associated with adverse pregnancy outcome after controlling for the effects of MSAFP and hCG (OR 2.5, 95% CI 1.13-5.55; P < .02).

CONCLUSION

One in three women with a false-positive screen for Down syndrome may experience an adverse pregnancy outcome. In this study, unconjugated E3 of 0.75 MoM or less appeared to be a better predictor of adverse pregnancy outcome than were MSAFP and hCG levels.

Expression of SRY transcripts in preimplantation human embryos

We have examined the expression of SRY mRNA in individual in vitro fertilized preimplantation human embryos; because of ethical constraints, these studies were confined to embryos with one and three pronuclei. Using a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we observed SRY mRNA at the one-cell through the blastula stages but not in spermatozoa. These results indicate that the de novo transcription of this sex-specific gene occurs at a developmental time considerably earlier than that of gonadal differentiation. Our results also indicate that in vitro fertilized embryos with one pronucleus are likely to be diploid.

Isolated choroid plexus cyst(s): an indication for amniocentesis

OBJECTIVE

Our purpose was to prospectively evaluate the risk of chromosomal abnormalities associated with isolated choroid plexus cyst(s) in gravid women undergoing second-trimester ultrasonographic examination.

STUDY DESIGN

During a 24-month period 9100 pregnant women underwent midtrimester ultrasonographic evaluation. Women with a fetal diagnosis of choroid plexus cyst(s) were offered amniocentesis and a repeat examination in 4 to 6 weeks.

RESULTS

A diagnosis of choroid plexus cyst(s) was made in 102 fetuses (1.1%). In four of these fetuses multiple congenital anomalies were noted. Three of the four fetuses had a chromosomal abnormality, two trisomy 18 and one unbalanced translocation, t(3;13). In the remaining 98 fetuses the choroid plexus cysts were isolated findings, that is, there were no other ultrasonographically detected anomalies. Seventy-five of these 98 fetuses underwent amniocentesis. An abnormal karyotype was identified in four fetuses: three had Down syndrome (two trisomy 21 and one unbalanced translocation, t[14;21]), and one trisomy 18. The offspring of the 23 patients in which amniocentesis was declined were phenotypically normal.

CONCLUSIONS

In our prospective study the risk of chromosomal abnormality with isolated choroid plexus cyst(s) was 1:25, a risk that exceeds the 1:200 risk of pregnancy loss after amniocentesis and the 1:126 and 1:260 risk for aneuploidy and Down syndrome, respectively, in a 35-year-old pregnant women during the midtrimester. These findings indicate that amniocentesis should be offered to pregnant women in the presence of isolated fetal choroid plexus cyst(s).

Sexual differentiation and preimplantation cell growth

Growth rates of human preimplantation embryos fertilized in vitro were assessed and compared to the sex of the pregnancy outcome. The likelihood of a liveborn male was significantly greater than that of a female if the mean number of cells/embryo was four or greater at the scheduled time of transfer (odds ratio of 6:1). This finding suggested that the Y chromosome expresses factors which influence embryonic growth rates immediately after fertilization.

Preimplantation genetics: a case for prospective action

Preimplantation genetics describes a newly-emerging field in medical genetics, the consequence of the implementation of clinical preimplantation diagnosis and the likely future development of germ-line gene therapy. Given the existing clinical and laboratory difficulties already demonstrated in preimplantation diagnosis and the sensitive ethical issues surrounding genetic manipulation of human embryos, there is a need for 1) critical and objective evaluation of developments in this field by human and medical geneticists and 2) development of guidelines for research and clinical practice in the years ahead. We propose a course of prospective action for preimplantation genetics implemented through the newly-formed American College of Medical Genetics in order to address the ethics, safety, accuracy, cost, and overall merit of preimplantation genetics.

Characterization of marker chromosomes by microdissection and fluorescence in situ hybridization

We characterized by microdissection and fluorescence in situ hybridization (FISH) two marker chromosomes: (1) a de novo, acrocentric marker chromosome detected in 88 per cent of the amniotic fluid cells of one of two physically and developmentally normal twins; and (2) a metacentric marker chromosome present in a phenotypically normal female. Analysis of FISH probes developed from the marker chromosomes indicated that the marker chromosomes in cases 1 and 2 were del(14)(q11) and a derivative chromosome from a Robertsonian translocation, respectively. Microdissection in combination with FISH may prove to be a valuable technique in determining the chromosomal origin of de novo marker chromosomes and unbalanced structural rearrangements detected during prenatal diagnosis.

Cell-type-specific adhesion mechanisms mediated by fibronectin adsorbed to chemically derivatized substrata

Plasma fibronectin (pFN) adhesion mechanisms on inert substrata were evaluated for murine fibroblasts (3T3) and human neuroblastoma (Platt) cells using glass coverslips chemically derivatized with a self-assembled monolayer of aliphatic chains terminated with a specific endgroup to interact with adsorbed pFN: [CH3], [SH], [SCOCH3], [NH2], [SO3H], or underivatized glass [SiOH]. All surfaces bound similar amounts of pFN and facilitated attachment of both cell types within narrow ranges. However, spreading/differentiation responses of cells differed considerably among the surfaces. While 3T3 cells spread and developed microfilament stress fibers comparably on all surfaces, inclusion of an RGDS-containing synthetic peptide in the medium revealed variation in resistance to stress fiber formation mediated by an RGDS-recognizing integrin: [NH2] greater than [CH3] much greater than [SiOH],[SH],[SCOCH3]. Different patterns of neurite formation were observed for neuroblastoma cells: [SiOH], [SO3H] greater than [SCOCH3],[SH] much greater than [CH3] greater than [NH2]. Similarity in cell responses to both [CH3] and [NH2] surfaces argues against a pattern dependent upon the hydrophobicity of substrata. When pFN was diluted to a subsaturable concentration with albumin for adsorption, neuroblastoma responses changed significantly from those observed on pFN-saturated surfaces, for both spreading and neurite generation: [NH2],[SO3H] much greater than [SH], [SCOCH3] greater than [SiOH],[CH3]. Responses to the pFN: albumin mixture were markedly improved from responses after sequential adsorptions, demonstrating "optimization" of pFN conformation (not merely binding) by coadsorption of albumin molecules. In most cases, the [NH2] surface yielded responses distinctively different from the other surfaces. Overall, these data suggest many variations in the conformation of pFN molecules adsorbed to specific inert surfaces, as well as variations in the responses of cell surface receptors to conformationally specific pFNs. They also reveal cell-type-specific changes in differentiated cell responses on derivatized substrata, mediated by different classes of cell surface receptors for the two cell types, and provide optimism for regulating FN-dependent adhesion mechanisms in either positive or negative contexts on biomaterial surfaces derivatized with one or more of these chemical end-groups.

A randomized comparison of transcervical and transabdominal chorionic-villus sampling. The U.S. National Institute of Child Health and Human Development Chorionic-Villus Sampling and Amniocentesis Study Group

BACKGROUND

Chorionic-villus sampling is done in early pregnancy to obtain fetal cells for the prenatal diagnosis of genetic and chromosomal defects. Transcervical chorionic-villus sampling has been shown to be safe and effective in national trials. Recently, an alternative transabdominal technique has been suggested as potentially easier and safer.

METHODS

From April 1987 through September 1989, we prospectively compared transcervical and transabdominal chorionic-villus sampling in 3999 women with singleton pregnancies in whom the risk of a genetically abnormal fetus was increased. Women between 7 and 12 weeks of gestation underwent ultrasonographic evaluation of placental and uterine position. Those with active vaginal infections, active bleeding, or cervical polyps were excluded. If the obstetrician thought either sampling procedure was acceptable, the woman was asked to consent to random assignment to one of the two procedures. Both groups were followed to determine the outcome of pregnancy and the rate of spontaneous fetal loss after chorionic-villus sampling.

RESULTS

Among the 3999 women who entered the study, sampling was attempted in 3873 (97 percent), 1944 of whom had been assigned to undergo transcervical sampling and 1929 to undergo transabdominal sampling. Of these 3873 women, sampling was eventually successful in 3863. Sampling was successful after a single insertion of the sampling instrument in 94 percent of the transabdominal procedures and 90 percent of the transcervical procedures. Among the women with cytogenetically normal pregnancies who had sampling because of maternal age, the rate of spontaneous fetal loss through 28 weeks of pregnancy was 2.5 percent in the transcervical-sampling group and 2.3 percent in the transabdominal-sampling group (difference, 0.26 percent; 95 percent confidence interval, -0.5 to 1.0 percent).

CONCLUSIONS

Transabdominal and transcervical chorionic-villus sampling appear to be equally safe procedures for first-trimester diagnosis of fetal abnormalities.

The risk and efficacy of chorionic villus sampling in multiple gestations

Chorionic villus sampling (CVS) in the first trimester of pregnancy provides a safe and effective method for the early prenatal diagnosis of cytogenetic abnormalities in multiple gestations. In this multicentre study involving 126 twin and 2 triplet gestations primarily at risk because of advanced maternal age, the overall success rate of obtaining an adequate villus sample from each fetus was 99.2 per cent. For women of advanced maternal age, the rate of combined losses of chromosomally normal fetuses due to spontaneous abortion, stillbirths, and neonatal deaths was 5.0 per cent, compared with a 4.0 per cent total loss rate following CVS in singleton pregnancies derived from the same population (Rhoads et al., 1989). There was a 100 per cent success rate in obtaining a cytogenetic analysis; a cytogenetic abnormality was present in five of the multiple gestations (3.9 per cent) and involved seven fetuses (2.7 per cent). There were no diagnostic errors and no cases of normal cytogenetic diagnosis followed by the birth of a cytogenetically abnormal newborn. Based on cases of XX/XY admixture, cell contamination derived either from maternal decidua or the other twin occurred in 6 of 256 samples (2.3 per cent), giving an overall estimate of the frequency of cell contamination of 4.6 per cent; these cases did not present a diagnostic problem. However, there were two cases (0.8 per cent) in which the fetal sex was incorrect, due either to complete maternal cell contamination or to the possibility that in error one twin was sampled twice.