There is a risk of multiples, which includes twins, triplets, or more. Multiple pregnancies can be risky for both the babies and the mother. It's important to discuss with your doctor how many embryos to transfer, as transferring more than necessary will increase your risk of conceiving twins or more. When embryos have been tested with PGT, typically only a single embryo is transferred.

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.
Injectable medication cycle with IUI: If pregnancy doesn't result from ovulation induction with oral medications, the next step is to use injectable medications. These medications stimulate the ovaries to produce two to four eggs; when combined with IUI, you have an increased possibility of conception. Essentially, the sperm is given more targets to hit. You will come into the office for four to eight monitoring appointments to track egg development and cycle timing.
If you fit one of these profiles, your fertility team may agree that it makes sense to attempt IUI before considering IVF. Before you begin IUI, it’s good to have a conversation with your partner and doctor about how many cycles you want to attempt. Many people place a limit of three failed IUI cycles, but others may try up to six before moving on.
Obesity: The obesity epidemic has recently become is a serious issue, particularly in industrialized nations. The rising number of obese individuals may be due in part to an energy-rich diet as well as insufficient physical exercise.  In addition to other potential health risks, obesity can have a significant impact on male and female fertility. BMI (body mass index) may be a significant factor in fertility, as an increase in BMI in the male by as little as three units can be associated with infertility. Several studies have demonstrated that an increase in BMI is correlated with a decrease in sperm concentration, a decrease in motility and an increase DNA damage in sperm. A relationship also exists between obesity and erectile dysfunction (ED). ED may be the consequence of the conversion of androgens to estradiol. The enzyme aromatase is responsible for this conversion, and is found primarily in adipose tissue. As the amount of adipose tissue increases, there is more aromatase available to convert androgens, and serum estradiol levels increase. Other hormones including inhibin B and leptin, may also be affected by obesity. Inhibin B levels have been reported to decrease with increasing weight, which results in decreased Sertoli cells and sperm production. Leptin is a hormone associated with numerous effects including appetite control, inflammation, and decreased insulin secretion, according to many studies. Obese women have a higher rate of recurrent, early miscarriage compared to non-obese women.
Treatment with Clomid tablets plus IUI improves fertility rates. For unexplained infertility, studies have shown that for women under 35, monthly success rates for Clomid plus insemination are about 10% per cycle. This pregnancy rate holds up for about 3 tries and the success rate is considerably lower after that. More about success rates with IUIs is on the insemination page and on the Clomid for unexplained infertility page. The insemination component boosts fertility more than the Clomid does - but success rates are higher when both are used together.
Psychological factors: Studies on infertile groups of men and women have produced contradictory findings of the importance of psychological factors in causing infertility. Emotional disturbances undoubtedly appear to have some significance. This is only reasonable if you realize that the whole hormonal cycle, with its delicate adjustments, is controlled from the brain. This is an area which needs further investigation.
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.
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The Catechism of the Catholic Church, in accordance with the Catholic understanding of natural law, teaches that reproduction has an "inseparable connection" to the sexual union of married couples.[128] In addition, the church opposes IVF because it might result in the disposal of embryos; in Catholicism, an embryo is viewed as an individual with a soul that must be treated as a person.[129] The Catholic Church maintains that it is not objectively evil to be infertile, and advocates adoption as an option for such couples who still wish to have children.[130]

The cost of an IUI is almost certainly less on a per cycle basis, but because IVF has much higher success rates and IUI is a poor option for some, the higher per cycle cost of IVF can actually be more affordable in the long run – in terms of the cost to bring home a baby.  Because most successful IUIs happen in the first three or four-cycle, it eventually becomes very expensive to bring home a baby with an IUI.

Nowadays, there are several treatments (still in experimentation) related to stem cell therapy. It is a new opportunity, not only for partners with lack of gametes, but also for homosexuals and single people who want to have offspring. Theoretically, with this therapy, we can get artificial gametes in vitro. There are different studies for both women and men.[65]
Only 30 percent of patients who receive 100 mg of Clomiphene a day will produce more than three follicles. Patients that produce less than than three follicles have about half the chance of getting pregnant than those that produce greater than three follicles. Patients that receive fertility medications but do not do an insemination have only half the success rates compared to those who do.
All pregnancies can be risky, but there are greater risk for women who are older and are over the age of 40. The older the women the riskier the pregnancy. As women get older, they are more likely to suffer from conditions such as gestational diabetes and pre-eclampsia. If older women do conceive over the age of 40, their offspring may be of lower birth weight, and more likely to requires intensive care. Because of this, the increased risk is a sufficient cause for concern. The high incidence of caesarean in older mothers is commonly regarded as a risk.

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]

^ Baker VL, Luke B, Brown MB, Alvero R, Frattarelli JL, Usadi R, et al. (September 2010). "Multivariate analysis of factors affecting probability of pregnancy and live birth with in vitro fertilization: an analysis of the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System". Fertility and Sterility. 94 (4): 1410–6. doi:10.1016/j.fertnstert.2009.07.986. PMID 19740463.

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."

Addressing lifestyle issues is not meant to be a quick fix, and typically does not lead to instant success. However, with unexplained infertility every little bit counts, so don’t fret or give up. Do not assume just because the cause of infertility is unexplained, it is untreatable or there is no pathway to parenthood. When a specific cause is not determined for women, and male infertility has also been ruled out, our fertility specialist may begin a course of treatment to improve the chances of conception and pregnancy. The speed with which interventions are offered depends on each individual’s own needs and desires as determined by age and other factors.