Genetic diagnosis of the preimplantation embryo

Novel uterine lavage system for recovery of human embryos fertilized and matured in vivo

Purpose: In this paper we describe a novel uterine lavage system for the recovery of in vivo preimplantation embryos. Currently, no other method exists to retrieve preimplantation embryos except for in vitro fertilization (IVF).

Methods: A single center, prospective feasibility study was conducted to test a novel uterine lavage system for the recovery of in vivo preimplantation embryos in egg donors and patients seeking pregnancy. Subjects were placed on controlled ovarian hyperstimulation followed by intrauterine insemination (IUI) and uterine lavage performed approximately 4–6 days after IUI. Subjects were followed up for 30 days after the procedure to monitor for safety events.

Results: A total of 134 uterine lavage cycles were performed on 81 subjects (average: 1.7 cycles/subject). Ova (oocytes or embryos) were collected in 53% (71/134) of the cycles with steady improvement of recovery efficiency over the course of the study, and embryos collected in 42% (56/134) of cycles. Embryos of many stages were collected, but 71% (96/136) of embryos collected were blastocyst stage embryos which are at the most advanced stage of embryogenesis. Embryos recovered were of good quality based on blastocyst gradings in which 74% (70/95, 1 blastocyst not graded) of the blastocysts were good quality as determined by the Gardner Scale of Morphology. The procedure was well tolerated with minor side effects. In 8% of cycles a positive hCG was observed after the lavage indicating some embryos were not recovered by the lavage system.

Conclusion: Through this work the system has been shown to recover embryos from the uterus in a safe and effective manner, thus opening the possibility that uterine lavage may serve as an alternative to IVF where patient indications allow.

Review: preimplantation diagnosis of inherited disease

Preimplantation diagnosis of inherited diseases has become possible with the techniques of in vitro fertilization, blastomere biopsy of the 6- to 10-cell embryo and DNA analysis of the single blastomeres. Disease-free embryos are selected for transfer to the uterus, thereby avoiding the need for termination of a fetus diagnosed as affected in prenatal diagnosis in the first or early-second trimester of pregnancy. The genetic indications for preimplantation diagnosis are theoretically the same as for prenatal diagnosis, but the defects must be detectable by the polymerase chain reaction. For X-linked recessive diseases, fluorescence in situ hybridization can be used as an alternative for the selection of female embryos. So far almost 40 healthy children have been born worldwide after preimplantation diagnosis for genetic disease. The possibilities and limitations of preimplantation diagnosis, especially in prevention of inherited disease, are discussed in this review.

Assisted reproductive technologies: genetic and nursing implications

The convergence of the fields of clinical genetics and assisted reproductive technologies is providing couples at risk for transmitting a genetic disorder to their children with new reproductive alternatives. The ability to test the preimplantation embryo for genetic anomalies, sort for X- and Y-bearing sperm, and improve genetic screening of gamete donors and couples at risk for a genetic disorder, are examples of these alternatives. The scope of nursing practice will be affected by the integration of these technologies into the health care offered to consumers. Opportunities also will exist for nurses to assist in the redefinition of health and illness that will be the serendipitous outcome of these scientific advances.

Superovulation fails to increase human blastocyst yield after uterine lavage

Uterine lavage affords the potential for non-invasive human blastocyst recovery, with obvious potential for preimplantation genetic diagnosis. In an effort to duplicate in women the multiple blastocyst recovery per cycle that can be achieved in several other species, we initiated a programme in which fertile women underwent superovulation, followed by lavage and embryo collection. We superovulated 15 fertile women, aged 21-40, in 29 cycles using one of four regimens. Insemination was by either intercourse or artificial intracervical donor insemination with cryopreserved sperm from men of proven fertility. In 28 of 29 cycles, the uterus was lavaged daily for 1, 2, or 3 days between 5 and 10 days after human chorionic gonadotropin (hCG) administration or luteinizing hormone (LH) surge. Almost total fluid volume was recovered in every lavage. There were no retained pregnancies and no complications. Surprisingly, only two morulae, one blastocyst, and four unfertilized ova were recovered. Thus, alterations in ovulation induction, insemination timing, or lavage techniques must be contemplated in order to increase the blastocyst yield and thus fulfil the potential of uterine lavage for preimplantation diagnosis.

Human gene therapy: ethics and public policy

The first three human gene transfer/therapy clinical protocols are now underway after having been subjected to an extensive review process by the Recombinant DNA Advisory Committee (RAC) and its Human Gene Therapy Subcommittee. The "Points to Consider" document developed by the RAC established the framework for evaluating genetic intervention protocols. This review process is taking place in a broader social context. Public attitude surveys in this country have indicated a general lack of knowledge in the area of genetic engineering but an acceptance of somatic-cell gene therapy as treatment for disease. Internationally, numerous policy statements on human genetic intervention have been published, all of which support the moral legitimacy of somatic-cell gene therapy for the cure of disease. The debate over the ethical issues related to somatic-cell gene therapy has evolved over a ten-year-period. The time has now come to begin a formal public process for the ethical assessment of germ-line genetic intervention.

Antenatal diagnosis of beta-thalassemia in Sardinia

This paper reviews the characteristics and the results of 15 years of experience with a preventive program, based on carrier screening and prenatal diagnosis, designed to control thalassemia major in the Sardinian population. The education of the population about thalassemia and the modalities for its prevention was accomplished via the mass media. Carrier screening was carried out voluntarily on couples of child-bearing age. Prenatal diagnosis was initially carried out by fetal blood analysis; since 1983, it has been done by DNA analysis on non-amplified or amplified DNA. Different chorionic villous sampling procedures have been used. Nowadays, we have adopted the transabdominal approach because, in our experience, it seems to be associated with a low risk (2%) of fetal mortality. At the present time, the beta-thalassemia mutations are detected directly by dot-blot analysis of amplified DNA with 32P- or horseradish peroxidase-labeled allele-specific oligonucleotide probes. Two oligonucleotide probes, one complementary to the codon-39 nonsense mutation, which accounts for 95.7% of the beta-thalassemia chromosomes in the Sardinian population, and the other complementary to the frameshift at codon 6, which is the second most common mutation in our population (2.1%), allow us to make prenatal diagnosis in the large majority of cases. Notwithstanding a careful dissection of maternal decidua from chorionic villi, co-amplification of maternal sequence was detected in 4 out of 425 cases tested by this procedure. In order to avoid this pitfall, the simultaneous amplification of highly polymorphic VNTR (variable number of tandem repeats) segments could be used. On the whole we have so far carried out 2711 prenatal tests: 1130 by fetal blood analysis, 1156 by oligonucleotide hybridization on electrophoretically separated DNA fragments, and 425 by dot-blot analysis on amplified DNA with allele-specific oligonucleotide probes. Two errors occurred by fetal blood analysis and none by DNA analysis. The incidence of thalassemia major declined from 1:250 live births in the absence of prevention to 1:1000 after the establishment of this program, indicating that carrier screening and prenatal diagnosis are effective means for preventing thalassemia major at the population level.