IVF may be used to overcome female infertility when it is due to problems with the fallopian tubes, making in vivo fertilisation difficult. It can also assist in male infertility, in those cases where there is a defect in sperm quality; in such situations intracytoplasmic sperm injection (ICSI) may be used, where a sperm cell is injected directly into the egg cell. This is used when sperm has difficulty penetrating the egg. In these cases the partner's or a donor's sperm may be used. ICSI is also used when sperm numbers are very low. When indicated, the use of ICSI has been found to increase the success rates of IVF.
Regarding potential spread of HIV/AIDS, Japan's government prohibited the use of IVF procedures for couples in which both partners are infected with HIV. Despite the fact that the ethics committees previously allowed the Ogikubo, Tokyo Hospital, located in Tokyo, to use IVF for couples with HIV, the Ministry of Health, Labour and Welfare of Japan decided to block the practice. Hideji Hanabusa, the vice president of the Ogikubo Hospital, states that together with his colleagues, he managed to develop a method through which scientists are able to remove HIV from sperm.[39]
Intercourse must take place frequently, particularly before and around the time of ovulation, and the couple must have been trying to conceive for at least one year (6 months if the woman is over 35 years old). Using these criteria, about 10-20% of all infertile couples have unexplained infertility. However, the percentage of couples classified as having unexplained infertility will depend upon the thoroughness of testing and the sophistication of medical technology. 
Fertility expert Zita West has noticed this increase at her London clinic. "The main reason," she explains, "is age. Women are having babies later." Exhaustion also plays a part. "The sleeplessness of life with a small child can't be underestimated," she says. "You might still be breastfeeding, you might be sharing a bed with a toddler, you might be holding down a job at the same time. Basically, there's not a lot of sex happening."
Intrauterine insemination (IUI) and in vitro fertilization (IVF) have been the therapeutic mainstays for those with unexplained infertility. The former involves inserting sperm directly into the uterus, while the latter works by uniting the sperm and the egg cells in a laboratory dish. IVF is expensive, but has a higher success rate. However, some patients continue to struggle and suffer the associated financial burden of repeated cycles.
In the natural process of conception without treatment, a woman’s ovaries produce a mature egg each month, which leaves the ovary and travels along the fallopian tube towards the uterus. Sperm that has been deposited in the vagina through intercourse travels through the cervix through the uterus and up the fallopian tube toward the egg. Millions of sperm are lost in the cervix and do not travel to the fallopian tube. When the two meet, they join to form the early stage of an embryo which then travels down the fallopian tube into the uterus. If all goes well, it will implant in the lining of the womb and pregnancy begins.
The Fallopian tubes are the site for fertilization before the embryo makes its way to the uterine cavity for implantation. If the Fallopian tubes are damaged, fertilization may not occur. If one Fallopian tube is blocked, it may be due to inherent disease involving both Fallopian tubes; even if the other Fallopian tube is open, it may not be able to provide the appropriate nurturing environment for fertilization and early embryo growth to take place.
^ Tan K, An L, Miao K, Ren L, Hou Z, Tao L, Zhang Z, Wang X, Xia W, Liu J, Wang Z, Xi G, Gao S, Sui L, Zhu DS, Wang S, Wu Z, Bach I, Chen DB, Tian J (March 2016). "Impaired imprinted X chromosome inactivation is responsible for the skewed sex ratio following in vitro fertilization". Proceedings of the National Academy of Sciences of the United States of America. 113 (12): 3197–202. Bibcode:2016PNAS..113.3197T. doi:10.1073/pnas.1523538113. PMC 4812732. PMID 26951653.
Previous tests should be carefully reviewed to ensure that the diagnosis is, in fact, "unexplained," and that no test has been omitted or missed. It may sometimes be necessary to repeat certain investigations. For example, if a previous laparoscopy has been done by a single puncture and reported as normal, it may be necessary to repeat the laparoscopy with a double puncture, to look for early endometriosis. 
Apart from poor egg quality at advanced maternal age, older women are also less likely to respond to ovarian stimulation hormones that cause the release of multiple eggs. Being able to produce a dozen of eggs significantly increases the odds of success. It allows your fertility practitioner to choose the egg with normal genetic makeup and best likelihood of implantation. In both nature and IVF, not all eggs are suitable to produce a pregnancy. Ideally, you would produce 8-15 eggs after ovarian hyperstimulation so that some of them are genetically normal and perfectly matured.
Success rates for IVF also vary according to individual circumstances, with the most significant factor again being the age of the woman. At RMA, the likelihood of live birth after transfer of a single, genetically normal blastocyst is 60-65% on average. It is a legal requirement in the US for success rates of fertility clinics to be reported to the CDC. This includes live birth rates and other outcomes. The Society for Assisted Reproductive Technology also reports on these statistics. All of our RMA clinics report their results individually and you can check them in the published data. You should remember that results for different clinics are not always comparable with each other because of differences in the patient base.
Repeated failed rounds of IVF can help identify causes of infertility. For example, if sperm and egg quality are normal, then the conception issue may be rooted at the embryonic or implantation level. In other words, if IVF fails to result in pregnancy despite successful fertilization, embryonic development or implantation may be to blame. Still this is a very expensive way to start getting answers.