There can be medical causes of SI, says West. "The thyroid is always something we check. Birth can put the thyroid out of kilter." Anwen, a woman in her 40s, tried for five years to have a second child. "I had my daughter when I was 30," she says, "which, at the time, seemed very early. I was the first among all our friends to have a baby." She decided to try for a second when her daughter was three. "But a year went by and nothing happened. I went to the GP and he told me not to worry. 'If you've already given birth, there won't be a problem,' he said. But my daughter turned five and I still wasn't pregnant." Eventually, Anwen persuaded her GP to refer her to a fertility consultant who, after some simple investigations, informed her she had polycystic ovarian syndrome. "He said I'd probably had it all my life and that my daughter was an amazing one-off. I had no idea that anything was wrong." She was given a prescription for the fertility drug Clomid; two months later, she conceived her son.

This chart is US national average data on success rates per IVF cycle by female age for 2014. The dark blue line (triangles) shows pregnancy rates per cycle by age. The orange line (circles) shows live birth rates per cycle by age. The rate of singleton live births per cycle is shown by the light blue line. The difference between "pregnancy" rate and "live birth" rate is due to miscarriages.
Fertilization. An embryologist (a scientist who specializes in eggs, sperm, and embryos) will examine your eggs before combining them with your partner's sperm and incubating them overnight. Fertilization usually happens during this time, but eggs that aren't normal may not be fertilized. (If sperm quality is poor, or if fertilization was unsuccessful during previous IVF cycles, your doctor may recommend using a technique called intracytoplasmic sperm injection (ICSI). With ICSI, a single sperm is injected directly into each mature egg.)
For most couples having difficulty achieving a pregnancy their chance of achieving a pregnancy is not zero, it is just lower than the average rate of conception—unless both Fallopian tubes are completely blocked, there is no sperm, or the woman never ovulates. Ovulation induction (or superovulation) with IUI helps patients to achieve pregnancy rates closer to the natural per cycle chance of pregnancy for women in their age group who do not have infertility (see fig 1). 

Complexity. IUI refers to one procedure. Prepared sperm is placed directly in the patient’s uterus when she is ovulating in order to aid fertilization. IUI may be performed in sync with a woman’s natural cycle or timed with fertility medications to stimulate ovulation. IVF, on the other hand, is a process which consists of several stages and requires more than one procedure: first the ovaries are stimulated using a series of fertility medications, then the patient undergoes egg retrieval in a day procedure under a mild anesthetic, then after embryos have been created and incubated in the lab, they are placed directly into her uterus in the embryo transfer procedure. Even with the use of fertility drugs, going through IUI is less physically demanding than undergoing IVF.
The major complication of IVF is the risk of multiple births. This is directly related to the practice of transferring multiple embryos at embryo transfer. Multiple births are related to increased risk of pregnancy loss, obstetrical complications, prematurity, and neonatal morbidity with the potential for long term damage. Strict limits on the number of embryos that may be transferred have been enacted in some countries (e.g. Britain, Belgium) to reduce the risk of high-order multiples (triplets or more), but are not universally followed or accepted. Spontaneous splitting of embryos in the womb after transfer can occur, but this is rare and would lead to identical twins. A double blind, randomised study followed IVF pregnancies that resulted in 73 infants (33 boys and 40 girls) and reported that 8.7% of singleton infants and 54.2% of twins had a birth weight of less than 2,500 grams (5.5 lb).[35]
The Rand Consulting Group has estimated there to be 400,000 frozen embryos in the United States in 2006.[83] The advantage is that patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy. Spare oocytes or embryos resulting from fertility treatments may be used for oocyte donation or embryo donation to another woman or couple, and embryos may be created, frozen and stored specifically for transfer and donation by using donor eggs and sperm. Also, oocyte cryopreservation can be used for women who are likely to lose their ovarian reserve due to undergoing chemotherapy.[84]
Sunni Muslim nations generally allow IVF between married couples when conducted with their own respective sperm and eggs, but not with donor eggs from other couples. But Iran, which is Shi'a Muslim, has a more complex scheme. Iran bans sperm donation but allows donation of both fertilised and unfertilised eggs. Fertilised eggs are donated from married couples to other married couples, while unfertilised eggs are donated in the context of mut'ah or temporary marriage to the father.[176]
Ovary stimulation. For eight to 14 days near the beginning of your menstrual cycle, you take a gonadotropin, a type of fertility drug that stimulates your ovaries to develop multiple mature eggs for fertilization (instead of just one). You also need to take a synthetic hormone like leuprolide or cetrorelix to keep your body from releasing the eggs too early.
Risk of multiples. IUI with fertility medication carries a significant risk of multiple pregnancies, including higher-order multiples (triplets or more). A good clinic will carefully monitor your follicles to make sure that only a safe number are mature before the IUI, but they cannot entirely eliminate the risk. Recent advances in IVF (including blastocyst transfer) mean that most modern fertility clinics now transfer only one or two embryos per IVF cycle. As a result, the risk of multiple pregnancies for IVF patients is much lower than it used to be.
Israel has the highest rate of IVF in the world, with 1657 procedures performed per million people per year. Couples without children can receive funding for IVF for up to two children. The same funding is available for women without children who will raise up to 2 children in a single parent home. IVF is available for women aged 18 to 45.[153] The Israeli Health Ministry says it spends roughly $3450 per procedure.
Regardless of pregnancy result, IVF treatment is usually stressful for patients.[42] Neuroticism and the use of escapist coping strategies are associated with a higher degree of distress, while the presence of social support has a relieving effect.[42] A negative pregnancy test after IVF is associated with an increased risk for depression in women, but not with any increased risk of developing anxiety disorders.[43] Pregnancy test results do not seem to be a risk factor for depression or anxiety among men.[43]

The treatment options for unexplained infertility are several and the treatment results are promising. Expectant management can be recommended if the woman is under 28-30 years of age and the infertility duration is less than 2-3 years. In vitro fertilization (IVF) has revolutionized the treatment of infertile couples, as well as profoundly increasing the basic understanding of human reproduction. IVF can be used as both a diagnostic and a therapeutic tool in couples with unexplained infertility. The pregnancy rates with IVF are good, at 40% per treatment cycle. In addition, the outcome of pregnancies among women with unexplained infertility is generally comparable to that of spontaneous and other pregnancies using assisted reproductive technologies.