Extracorporeal Embryos

Science fiction fantasies about the artificial uterus notwithstanding, only the very first stages of human development can occur outside the female body. Since 1978, in vitro fertilization followed by embryo transfer has been a common treatment of fertility problems. The growth of ovarian follicles is stimulated by the administration of gonadotropins. Oocytes are then collected by laparoscopy and placed in an appropriate culture medium. Sperm is added and cleavage occurs in culture until the blastocyst is transferred in the uterus.

With in vitro fertilization, the early embryo became much more accessible to human intervention, and this has raised ethically perplexing possibilities. Interventional research on early embryos has become possible, raising the question of whether it is ethical to produce human embryos for research purposes, or whether research should be done, if at all, only on "spare" embryos. These occur when some embryos are no longer needed for fertility treatment, even though they resulted from in vitro fertilization performed with therapeutic intent. Additionally, progress in genetic testing techniques using very small amounts of DNA has made preimplantation diagnosis of genetic abnormalities possible. Single blastomeres are removed from in vitro blastocysts, their DNA amplified by polymerase chain reaction (PCR), and subjected to genetic tests with appropriate DNA probes. (Thanks to regulative development, the missing blastomere is soon compensated for.) In this way, embryos can be screened for certain genetic defects and only those free of defects chosen for embryo transfer. This procedure is sometimes suspected of being eugenic, and the controversy around it has led to it being outlawed in certain countries including Germany and Switzerland.

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