In the laboratory, for ICSI treatments, the identified eggs are stripped of surrounding cells (also known as cumulus cells) and prepared for fertilisation. An oocyte selection may be performed prior to fertilisation to select eggs that can be fertilized, as it is required they are in metaphase II. There are cases in which if oocytes are in the metaphase I stage, they can be kept being cultured so as to undergo a posterior sperm injection. In the meantime, semen is prepared for fertilisation by removing inactive cells and seminal fluid in a process called sperm washing. If semen is being provided by a sperm donor, it will usually have been prepared for treatment before being frozen and quarantined, and it will be thawed ready for use.
We don't know what causes most cases of secondary infertility, says Jamie Grifo, M.D., Ph.D., program director of the New York University Fertility Center, in New York City. "The majority of the time, though, it reflects the fact that you're older now, so it's simply more difficult to get pregnant." The reality is that for women, fertility peaks at age 25 and drops by half between ages 30 and 40. As we age, egg quality declines and we're more likely to develop fibroids and endometriosis, which contribute to infertility. Other factors such as adding extra weight, taking new meds, or having surgery since your last pregnancy can be an issue. It may also be that your partner's sperm quality or production is now poor.
The eggs are then fertilized with sperm that has been optimized in the laboratory so that sperm with poor morphology or motility are discarded and the healthiest remain. Fertilization usually takes place through Intracytoplasmic Sperm Injection (ICSI). In this high-precision technique, the best single sperm are selected and individually microinjected into each egg.
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. 
Having no period means ovulation isn’t taking place at all, so a pregnancy can’t happen because no eggs is making itself eligible to be fertilized. Similarly, having irregular periods makes achieving pregnancy difficult, because it’s hard to time intercourse properly -- if sperm and egg aren’t at the same place at the same time, there is no chance of pregnancy.
Unlike the simpler process of artificial insemination -- in which sperm is placed in the uterus and conception happens otherwise normally -- IVF involves combining eggs and sperm outside the body in a laboratory. Once an embryo or embryos form, they are then placed in the uterus. IVF is a complex and expensive procedure; only about 5% of couples with infertility seek it out. However, since its introduction in the U.S. in 1981, IVF and other similar techniques have resulted in more than 200,000 babies.

In December 2015, the Ontario provincial government enacted the Ontario Fertility Program for patients with medical and non-medical infertility, regardless of sexual orientation, gender or family composition. Eligible patients for IVF treatment must be Ontario residents under the age of 43 and have a valid Ontario Health Insurance Plan card and have not already undergone any IVF cycles. Coverage is extensive, but not universal. Coverage extends to certain blood and urine tests, physician/nurse counselling and consultations, certain ultrasounds, up to two cycle monitorings, embryo thawing, freezing and culture, fertilisation and embryology services, single transfers of all embryos, and one surgical sperm retrieval using certain techniques only if necessary. Drugs and medications are not covered under this Program, along with psychologist or social worker counselling, storage and shipping of eggs, sperm or embryos, and the purchase of donor sperm or eggs.[151]
Problems in the quantity or quality of eggs: Women are born with a limited supply of eggs and are unable to create new eggs after birth. As women approach their 40s and beyond, the numbers of eggs left in their ovaries decrease, and the remaining eggs have a higher chance of having chromosomal problems. For women where age isn’t a concern, there are other reasons that they might have a low number of good quality eggs, including autoimmune or genetic conditions and prior surgery or radiation.
A review in 2013 came to the result that infants resulting from IVF (with or without ICSI) have a relative risk of birth defects of 1.32 (95% confidence interval 1.24–1.42) compared to naturally conceived infants.[48] In 2008, an analysis of the data of the National Birth Defects Study in the US found that certain birth defects were significantly more common in infants conceived through IVF, notably septal heart defects, cleft lip with or without cleft palate, esophageal atresia, and anorectal atresia; the mechanism of causality is unclear.[49] However, in a population-wide cohort study of 308,974 births (with 6,163 using assisted reproductive technology and following children from birth to age five) researchers found: "The increased risk of birth defects associated with IVF was no longer significant after adjustment for parental factors." [50] Parental factors included known independent risks for birth defects such as maternal age, smoking status, etc. Multivariate correction did not remove the significance of the association of birth defects and ICSI (corrected odds ratio 1.57), although the authors speculate that underlying male infertility factors (which would be associated with the use of ICSI) may contribute to this observation and were not able to correct for these confounders. The authors also found that a history of infertility elevated risk itself in the absence of any treatment (odds ratio 1.29), consistent with a Danish national registry study [51] and "implicates patient factors in this increased risk." The authors of the Danish national registry study speculate: "our results suggest that the reported increased prevalence of congenital malformations seen in singletons born after assisted reproductive technology is partly due to the underlying infertility or its determinants."
Additionally, couples may turn to assisted reproductive technology, the most common of which is in vitro fertilization (IVF). Other techniques may include special injections or using a donor's eggs or sperm. Complications can sometimes occur, the most common being bleeding or infection; ovarian hyperstimulation syndrome, in which the ovaries become swollen and painful; and multiple pregnancies.
The second study by Huang et al. demonstrated nearly equivalent pregnancy rates between the three medications. Furthermore, the twin risk was not significantly elevated in any of the three groups. The key difference between these studies is that the dose of gonadotropins was higher in the AMIGOS study (150 units) than the Huang study (75 units). A higher dose often means more eggs ovulated and a greater risk of twins or more.
If you're not pregnant, you'll stop taking progesterone and likely get your period within a week. If you don't get your period or you have unusual bleeding, contact your doctor. If you're interested in attempting another cycle of in vitro fertilization (IVF), your doctor might suggest steps you can take to improve your chances of getting pregnant through IVF.
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.