In vitro fertilization (IVF) – originally developed for the treatment of absolute tubal factor infertility – brings female and male gametes in close proximity in a petri dish outside the human body. Major steps in IVF include ovarian stimulation (aiming to stimulate maturation of multiple follicles), oocyte retrieval via transvaginal puncture to obtain multiple oocytes, fertilization of oocytes and the subsequent development of embryos under strictly controlled circumstances in the laboratory, the transfer of preferably a single, high-quality embryo into the uterine cavity and the freezing of surplus embryos, creating the possibility for additional chances of pregnancy when transferred in subsequent cycles. IVF success rates vary significantly, but current live birth rates are approximately 30 % per started IVF cycle; this represents a cumulative outcome involving the transfer of fresh and frozen embryos harvested from the same oocyte cohort. Intracytoplasmic sperm injection (ICSI) is the mechanical injection of a single sperm into the cytoplasm of an oocyte. This technology is able to generate pregnancies in couples with very poor sperm quality from their own genetic material. Such a sperm may be obtained from the ejaculate, or epididymal or testicular sperm may be obtained by surgical procedures. Currently, more than 60 % of all IVF cycles worldwide make use of the ICSI procedure. IVF can also be applied in many conditions not related to infertility per se, such as preimplantation genetic testing-diagnosis (PGT-D) of embryos in families with known congenital abnormalities, the preservation of fertility (for medical or non-medical reasons) by the cryostorage of ovarian tissue, oocytes or embryos, the use of donor oocytes or embryos, or the transfer of embryos into the uterus of another person allowing her (the ‘surrogate mother’) to carry the pregnancy.
