New frontiers of assisted reproductive technology (Chien Tien Hsu Memorial Lecture 2007)

Many significant advances have been made in assisted reproductive technology since the birth of the first baby conceived with in vitro fertilization and embryo transfer. The development of recombinant gonadotropins and gonadotropin releasing hormone antagonists helps to simplify the ovarian stimulation. Excessive ovarian stimulation should be avoided because of the risks of ovarian hyperstimulation syndrome and reduction in endometrial receptivity. Maturation of oocytes in vitro has been developed in some centers. It is still uncertain whether techniques such as assisted hatching, blastocyst transfer and pre-implantation aneuploidy screening can improve the live birth rates in assisted reproduction. The introduction of pre-implantation genetic diagnosis for selection of human lymphocyte antigens (HLA) compatible embryos for treatment of siblings has raised ethical concerns. There is a higher risk of obstetric complications and congenital abnormalities even in singleton pregnancies achieved with assisted reproduction. Because of the risks of multiple pregnancies, elective single embryo transfer is increasingly used in good-prognosis patients. With a good freezing program, the cumulative pregnancy rate (including the pregnancies from subsequent replacement of frozen-thawed embryos) is not adversely affected. Improvement in cryopreservation techniques has made it possible to cryopreserve slices of ovarian tissue or oocytes, thus helping women who have to receive sterilizing forms of anti-cancer treatment to preserve their fertility. It is important that the development of the new techniques should be based on good scientific evidence. Ethical, legal and social implications should also be considered before the introduction of new techniques.