State of the art of assisted human reproduction

Background: Infertility is a disease observed in approximately 10% of the reproductive age population (20-44 years old), and is defined as the failure to conceive after twelve months of regular sexual intercourse, without contraception; in women older than 35 years old, this period is reduced to 6 months. The main causes of infertility are tubal, ovarian and uterine and sperm abnormalities, endometriosis, and those with undetermined causes. Over the past 30 years, several techniques were developed to overcome these factors including gamete cryopreservation, controlled ovarian stimulation, intra-uterine insemination, in vitro fertilization, intracytoplasmatic sperm injection). Review: Despite advances in assisted reproductive technologies (ART), treatment success is still strongly dependent on oocyte and sperm quality, and resulting embryo viability. The most promising advance on oocyte quality assessment is the evaluation of the ovarian reserve by the quantification of the anti-müllerian hormone (AMH). Since ovarian reserve is closely related to oocyte quality, AMH levels could be an indicator of both oocyte production capacity and the potential of these oocytes to generate a viable embryo. On the other hand, despite the development of techniques to overcome male factor infertility, attention has been paid on the semen evaluation, since routine sperm evaluation techniques are known to be ineffective, especially in those cases of unexplained infertility. Therefore, techniques were developed to assess acrosome and membrane integrity, mitochondrial potential, DNA integrity, and fertilizing capacity of sperm. However, further studies are necessary to evaluate sperm DNA integrity without damaging the cell, allowing the injection of a spermatozoon with an intact DNA when using ICSI. Regarding embryo quality, even with a good quality oocyte (as assessed by the current techniques) and an apparently normal sperm, there are still chances of generating an embryo with genetic abnormalities. In such cases, and in cases of recurrent failures, women over 35 years of age, and couples with a pre-existing genetic risk, the preimplantation genetic diagnosis (PGD) appears to be an important tool to improve the odds of pregnancy and avoid abortions or the conception of fetuses with genetic abnormalities. The technique of PGD, usually performed with PCR or FISH, has gained a powerful tool with the development of the Comparative Genomic Hybridization (CGH). However, recent studies aiming to identify markers of oocyte and sperm quality and embryo viability are in course using mass spectroscopy. With this sensitive technique applied to body fluids (i.e., blood, follicular fluid, seminal plasma), granulosa cells, sperm, and culture media, researches are being conducted to non-invasively identify biomarkers that will help understand reproductive mechanisms and to efficiently predict the outcome of ARTs. Conclusion: Significant advances in ART have been observed in the last few years, yet, failures still occur with high frequency. This review will focus on techniques to assess oocyte quality, sperm function and embryo viability, aiming to provide tools for a precise prognosis when treating infertile couples.

Human assisted reproduction

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.