If neither surgery nor medical treatment can resolve the fertility barrier, assisted reproductive technology can be chosen to complete conception. 1. Intrauterine insemination Intrauterine insemination (IUI) is the placement of washed semen directly into the uterine cavity across the cervical barrier The main indications for IUI are cervical factor infertility, as well as oligospermia, immune infertility and semen delivery disorders (e.g. hypospadias). To ensure efficacy, IUI requires a minimum of 5-40X106 motile sperm in the semen. The success rate of intrauterine insemination varies widely and is directly related to the reproductive potential of the female partner. For male infertility, pregnancy rates range from 8-16% per IUI treatment cycle. The use of ultrasound and urinalysis to monitor ovulation can improve the success rate of IUI. 2. In vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) In vitro fertilization is a more complex technique than IUI, removing more of the hardships and obstacles that sperm encounter in the female reproductive tract. ivf involves controlled ovulation promotion and ultrasound-guided transvaginal acquisition of follicles prior to normal ovulation. The eggs are inseminated by 5×105-50×105 sperm in a covered Petri dish. This technique addresses fertility barriers in moderate and severe infertility with low sperm density. More recently, there has been a revolutionary advancement in IVF, namely microinjection of sperm, or ICSI. The number of live sperm required to fertilize an egg has been reduced from hundreds of thousands to 1. The introduction of ICSI has facilitated the development of sperm retrieval for patients with azoospermia. The technology has also pushed urologists to go beyond semen and explore the male reproductive tract for sperm to assist patients in completing biologically meaningful pregnancies. Currently, the sources of sperm cover the vas deferens, epididymis and testes. Two points to note are: (1) IVF and ICSI may avoid many of the barriers of natural selection in natural fertilization, allowing abnormal defects that cause infertility to be passed on to offspring. This is a big ethical issue, especially since X-linked disorders such as Klinefelter syndrome may be reproduced in their grandchildren, leading to treatable male infertility. (2) Recent data show that the rate of abnormal sex chromosomes in offspring born using this technique is four times higher than in offspring of natural pregnancies. 3. Pre-implantation genetic diagnosis Pre-implantation genetic diagnosis is a highly specific test that can precisely determine the genetic norm of the embryo. In some patients, heritable and life-threatening diseases may be passed on to offspring through IVF and ICSI techniques. For pre-implantation genetic diagnosis, individual cells are obtained from early embryos in a covered culture dish. The genetic material obtained from the cells is then tested to determine if the embryo under test carries abnormal chromosomes or genes. With the help of pre-implantation genetic diagnosis, early embryos resulting from IVF and ICSI can be individually examined for the presence of suspicious genetic characteristics. Due to their real-time nature, it is possible to determine within 24h whether to proceed with embryo transfer to ensure that lethal diseases are not passed down the line. It is clear that obtaining several cells from an embryo will not compromise the survival and normal development of most embryos.