Most invertebrates, like sea urchins, and non-mammalian vertebrates, such fish and amphibians, have spermatozoa that are fully capable of fertilizing eggs when they leave the testis. Mammalian testicular spermatozoa, on the other hand, lack this capability. They become more capable of fertilising as they move through the epididymis. The maturation of spermatozoa in the epididymis is referred to as this process, which appears to be "unique" to mammals. However, spermatozoa still need to go through a further stage of maturation or capacitation within the female genital canal before they may fertilise eggs. IVF was initially created as a way to get around a simple mechanical fallopian tube blockage, which prevents sperm from getting to the oocytes and, as a result, prevents embryos from getting to the uterus for implantation. Mature oocytes were removed from the ovaries by laparoscopy, cultured, and fertilized in vitro, and the resulting embryos were then transferred back to the patient's uterus for potential implantation. But by the early 1980s, it was clear that the methods might also be applied to treating infertility brought on by a variety of factors, such as male subfertility. The development of vaginal ultrasound-guided oocyte recovery techniques and improved superovulation medicines allowed the treatment cycle to be transformed into an outpatient procedure that may be performed safely and sucessfully
