Human assisted reproduction

ABSTRACT

Background: Infertility is defined as the failure to conceive after one year of unprotected intercourse, and this time has been lowered to 6 month if the female partner is older than 35 years. Infertile couples are offered to low and high complexity treatments are available according to their cause of infertility. Low complexity treatments comprise timed intercourse, intrauterine insemination with or without controlled ovarian stimulation. High complexity treatments comprise standard in vitro fertilization (IVF) and IVF by intracytoplasmatic sperm injection (ICSI). Additionally to these treatments, infertile patients might be benefited by accessory techniques such as preimplantational genetic screening and diagnosis. These techniques aim to detect the most common human aneuploydies related to abortion and chromosomal syndromes; and to identify embryos carriers of genetic diseases like talassemia, Huntington's disease, fragile-X syndrome among others. Human assisted reproduction is a dynamic branch of Medicine performed by several medical specialists from gynecologists to surgeons, and professional as nurses, biologists and veterinarians. Review Initially, human infertility was treated by intracervical insemination due to the risk of endometrial insemination and the occurrence of pelvic inflammation, but the development of better insemination techniques and instruments led to the report of a safe intrauterine insemination method in 1974. However, insemination was restricted to oligozoospermia or cervical factors and it was not able to overcome ovarian and tubal infertility factors, neither severe male infertility factor. The range of infertility treatment was tremendously broadened in 1978 with the report of the first IVF baby birth. Since then infertile couples due to tubal factors, ovarian and moderate male infertility factors started to be treated with IVF. Several changes in embryo culture conditions and instruments for IVF were developed and the technology was world wide spread. The first IVF baby was a girl born in 1984 in Brazil. Even though, some ovarian conditions and severe male factor infertility couldn't be treated until 1992. This landmark was the report of the first babies originated by in vitro fertilization with ICSI. In parallel to those scientific and medical evolutions, drugs and new protocols of controlled ovarian stimulation increased the number of oocytes available for fertilization and, consequently, the number of exceeding embryos. These spare oocytes and embryos required the development of cryopreservation techniques for long term storage. Slow rate freezing and vitrification of embryos were reported approximately 25 years ago, but just recently vitrification of oocytes and embryos became the first option for fertility preservation and/or embryo storage in humans. Preimplantational genetic screening and diagnosis were complementary techniques developed during the same period. These tests require precise and meticulous micromanipulation techniques and skills for the obtainment of a single blastomere with intact genetic material for screening of aneuploydies by fluorescent in situ hybridization or the detection of a deleterious allele by single cell PCR. New drugs, protocols, instruments and techniques for Human Assisted Reproduction are still under development in many Universities, infertility clinics and private companies aiming to increase the efficiency of infertility treatments. Conclusion: Human assisted reproduction is constantly evolving with the development of more precise diagnostic tests and with the improvement of clinical approaches to infertility and better conditions in embryology laboratories and this constant evolution is the result of the synergic interaction of clinical infertility specialists with researchers of different backgrounds.