One, two or three IVF treatments are government subsidised for women who are younger than 40 and have no children. The rules for how many treatments are subsidised, and the upper age limit for the women, vary between different county councils.[154] Single women are treated, and embryo adoption is allowed. There are also private clinics that offer the treatment for a fee.[155]
IUI is a procedure during which processed and concentrated motile sperm are inserted directly into a woman’s uterus. This procedure is timed according to a woman’s ovulation, and may be performed one to two times in the days immediately following the detection of ovulation. After ovulation a woman’s egg is picked up by the fallopian tube and waits there for the sperm. Since the IUI procedure deposits higher concentrations of good quality sperm close to where the egg is waiting, the chances that the egg and sperm will find one another are increased.
Cytoplasmic transfer is where the cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilised with sperm and implanted in a womb, usually that of the woman who provided the recipient egg and nuclear DNA. Cytoplasmic transfer was created to aid women who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm.
It was an awesome feeling when i found out that i am pregnant, i could not believe myself, after trying for 5 years now, finally i have been able to be called a proud mother of my baby boy. my husband is glad too, by standing by my side all through the struggles of infertility with strong feeling we will achieve this together. i am giving this hint to couples who are struggling with infertility, your time as come as well, with the help of Dr Micheal Casper pregnancy prescription medicine, herbal remedy, which i myself use to get pregnant with few weeks of using it as directed by the doctor. you can also have a child to call your own. this is the doctor contact [email protected]
Nonmedicated cycle with IUI: Also known as natural cycle IUI, a non-medicated cycle with IUI is often used by single women or same-sex female couples who are not directly experiencing infertility, but rather a lack of sperm. This treatment involves tracking the development of the egg that is naturally recruited during a menstrual cycle and then introducing the donated sperm. You will come into the office for two to four monitoring appointments to track egg development and cycle timing.
Amongst these two patient populations (which we’ll refer to now as PCOS), IUI with clomid and letrozole generally shows no improvement versus when these drugs are taken without IUI. When IUI is coupled with gonadotropins, success rates reach 14 - 26% per cycle, which is higher than almost any other patient class, but still pales in comparison to IVF. It’s also worth noting that PCOS patients who are taking gonadotropins have a very high risk of multiples.
IUI: An IUI can be done with no medications or a number of different medications to help develop and ovulate one or two eggs. Around day 14 of a woman’s cycle, the insemination takes place which deposits sperm inside the uterus. This greatly increases the number of sperm at the junction of the uterus and fallopian tubes, the distance they have to swim to meet the egg, and thus increases the chances of natural conception for many people.
In IVF, a woman is given more medications to develop lots of eggs. Ideally, they develop around 15 mature eggs. The eggs are removed from the ovaries, fertilized and developed in a lab for a number of days, and subsequently put back into the uterus as an early-stage embryo. While this may sound like a relatively minor difference, it leads to leads to a large number of noteworthy differences.
Cytoplasmic transfer is where the cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilised with sperm and implanted in a womb, usually that of the woman who provided the recipient egg and nuclear DNA. Cytoplasmic transfer was created to aid women who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm.

Infertility problems and miscarriage rates increase significantly after 35 years of age. There are now options for early egg retrieval and storage for women in their 20's. This will help ensure a successful pregnancy if childbearing is delayed until after age 35. This is an expensive option. However, women who know they will need to delay childbearing may consider it.


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.
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.
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.
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."

May you accept your body – even if you are an infertile man. We struggled with male factor infertility in our marriage, and it strengthened our marriage and our faith in God. May you feel God’s blessing on you even if you can’t conceive children naturally. May you walk in faith, and trust that He knows what He is doing. Don’t give up on your God, for He is loving and compassionate.
West states that the "hardest thing about secondary fertility issues is that you want a sibling for your child." Fiona, who has a son of five and has been trying to conceive a second child for two years, says she can no longer look out of the window at her son playing in the garden. "It breaks my heart. He just looks so alone out there. All I want is a sibling for him but I don't think it's going to happen."

ART techniques generally start with stimulating the ovaries to increase egg production. After stimulation, the physician surgically extracts one or more eggs from the ovary, and unites them with sperm in a laboratory setting, with the intent of producing one or more embryos. Fertilization takes place outside the body, and the fertilized egg is reinserted into the woman's reproductive tract, in a procedure called embryo transfer.


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.
Availability of IVF in England is determined by Clinical commissioning groups. The National Institute for Health and Care Excellence recommends up to 3 cycles of treatment for women under 40 years old with minimal success conceiving after 2 years of unprotected sex. Cycles will not be continued for women who are older than 40 years old.[156] CCGs in Essex, Bedfordshire and Somerset have reduced funding to one cycle, or none, and it is expected that reductions will become more widespread. Funding may be available in "exceptional circumstances" – for example if a male partner has a transmittable infection or one partner is affected by cancer treatment. According to the campaign group Fertility Fairness at the end of 2014 every CCG in England was funding at least one cycle of IVF".[157] Prices paid by the NHS in England varied between under £3,000 to more than £6,000 in 2014/5.[158] In February 2013, the cost of implementing the NICE guidelines for IVF along with other treatments for infertility was projected to be £236,000 per year per 100,000 members of the population.[159]
Those fearful of conceiving with multiples should strongly consider IVF and only transferring one embryo at a time. In these circumstances, just 1% of pregnancies lead to twins, and triplets are even more rare. Alternatively, 8 - 30% of medicated IUI pregnancies lead to twins. Finally, the least preferable circumstance is do to IVF with multiple embryo transfer, where in women under 38 years of age, 30% of pregnancies culminate in a multiple birth.

Give in to the grief. While you probably feel incredibly disappointed and sad about your infertility problems, you may feel guilty giving in to those emotions. Parents facing secondary infertility often feel they don’t have the “right” to feel sad about their struggles because they should be grateful for the child they already have. But if you want more children and are having trouble getting pregnant again, you are just as entitled as anyone else to feel depressed or angry. The last thing you need when you’re coping with secondary infertility is to let guilt weigh you down even more.
^ Manheimer E, van der Windt D, Cheng K, Stafford K, Liu J, Tierney J, Lao L, Berman BM, Langenberg P, Bouter LM (2013). "The effects of acupuncture on rates of clinical pregnancy among women undergoing in vitro fertilization: a systematic review and meta-analysis". Human Reproduction Update. 19 (6): 696–713. doi:10.1093/humupd/dmt026. PMC 3796945. PMID 23814102.
The stress of secondary infertility on an individual's life and relationships can be significant. It can be hard to find support from family and friends, especially when a woman or couple already has/have children. Sentiments such as, "you should be grateful for what you have," or, "just keep trying," almost never serve as useful advice or support. Couples and single parents can even experience resentment from other couples with infertility who are unable to even have their first child.
Preimplantation genetic screening (PGS) or preimplantation genetic diagnosis (PGD) has been suggested to be able to be used in IVF to select an embryo that appears to have the greatest chances for successful pregnancy. However, a systematic review and meta-analysis of existing randomised controlled trials came to the result that there is no evidence of a beneficial effect of PGS with cleavage-stage biopsy as measured by live birth rate.[81] On the contrary, for women of advanced maternal age, PGS with cleavage-stage biopsy significantly lowers the live birth rate.[81] Technical drawbacks, such as the invasiveness of the biopsy, and non-representative samples because of mosaicism are the major underlying factors for inefficacy of PGS.[81]

^ GBD 2015 Disease and Injury Incidence and Prevalence, Collaborators. (8 October 2016). "Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015". Lancet. 388 (10053): 1545–1602. doi:10.1016/S0140-6736(16)31678-6. PMC 5055577. PMID 27733282.


Insemination – This is done as close to the day of ovulation as possible. During insemination, washed and concentrated sperm is injected into the top of your uterus through a small catheter inserted through the vagina and cervix. Once injected, the catheter is removed. You can expect the insemination to take just a few minutes. It is possible to experience mild cramping post-procedure. The sperm used in your IUI can usually be collected at the office performing the IUI (preferred if possible), frozen and shipped to the center, collected fresh at your home and shipped to our centers using our sperm shipping kits (not advised), or ordered and sent to our office from a donor agency. Fresh semen samples are prepared in our laboratory to obtain a concentration of active sperm.
Secondary infertility is the inability to conceive a child or carry a pregnancy to full term after previously giving birth. To classify as secondary infertility, the previous birth must have occurred without help from fertility medications or treatments, like in vitro fertilization. Secondary infertility typically is diagnosed after trying unsuccessfully to conceive for six months to a year. A related condition is recurrent pregnancy loss where patients and couples are able to conceive but are unable to carry to term.
After a year of trying to conceive, couples should consider infertility as a possible reason and seek professional help. Women actively trying to get pregnant may wish to consult a doctor earlier if they are over the age of 40, have irregular or painful periods, have a history of miscarriages, have been diagnosed with pelvic inflammatory disease or endometriosis, or have been treated for cancer.

IVF is the most successful method of fertility treatment utilized today to help couples to conceive. The basic components of the IVF process include stimulation of the ovaries to produce multiple eggs at a time, removal of the eggs from the ovary (egg retrieval), fertilization of the eggs in the laboratory, and subsequent placement of the resulting embryos into the uterus (embryo transfer). The chance of pregnancy from IVF depends primarily on the age of the woman, the cause of infertility, and factors related to the quality of the IVF laboratory.
Artificial insemination, including intracervical insemination and intrauterine insemination of semen. It requires that a woman ovulates, but is a relatively simple procedure, and can be used in the home for self-insemination without medical practitioner assistance.[171] The beneficiaries of artificial insemination are women who desire to give birth to their own child who may be single, women who are in a lesbian relationship or women who are in a heterosexual relationship but with a male partner who is infertile or who has a physical impairment which prevents full intercourse from taking place.
Around one in 7 couples that require artificial reproductive treatment (ART) have "unexplained" infertility and doctors often first use approaches like ensuring the female partner's ovulation occurs at the same time as natural sex or artificial insemination/intrauterine insemination (IUI). They may then recommend IVF where thousands of the male partner's best sperm are purified and incubated with the egg — this is the preferred initial ART procedure in cases of "unexplained" infertility.
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.
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.
The stress of secondary infertility on an individual's life and relationships can be significant. It can be hard to find support from family and friends, especially when a woman or couple already has/have children. Sentiments such as, "you should be grateful for what you have," or, "just keep trying," almost never serve as useful advice or support. Couples and single parents can even experience resentment from other couples with infertility who are unable to even have their first child.
IUI is a procedure during which processed and concentrated motile sperm are inserted directly into a woman’s uterus. This procedure is timed according to a woman’s ovulation, and may be performed one to two times in the days immediately following the detection of ovulation. After ovulation a woman’s egg is picked up by the fallopian tube and waits there for the sperm. Since the IUI procedure deposits higher concentrations of good quality sperm close to where the egg is waiting, the chances that the egg and sperm will find one another are increased.
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.
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]

It is extremely difficult for those with unexplained infertility to know when to stop looking for a cause, to say “enough is enough.” You may feel you are entering a state of limbo. You may feel stuck unable to grieve and get on with other options because you hang on to those slender threads of hope that the cause of your infertility will be revealed in the next test or treatment. Your sadness may intensify as time passes and you find no medical or emotional resolution. Consider finding a Support Group or Mental Health Professional in your area.
For women, problems with fertilisation arise mainly from either structural problems in the Fallopian tube or uterus or problems releasing eggs. Infertility may be caused by blockage of the Fallopian tube due to malformations, infections such as chlamydia or scar tissue. For example, endometriosis can cause infertility with the growth of endometrial tissue in the Fallopian tubes or around the ovaries. Endometriosis is usually more common in women in their mid-twenties and older, especially when postponed childbirth has taken place.[55]
Assisted hatching. About five to six days after fertilization, an embryo "hatches" from its surrounding membrane (zona pellucida), allowing it to implant into the lining of the uterus. If you're an older woman, or if you have had multiple failed IVF attempts, your doctor might recommend assisted hatching — a technique in which a hole is made in the zona pellucida just before transfer to help the embryo hatch and implant. Assisted hatching is also useful for eggs or embryos that have been previously frozen as the process can harden the zona pellucida.
In egg donation and embryo donation, the resultant embryo after fertilisation is inserted in another woman than the one providing the eggs. These are resources for women with no eggs due to surgery, chemotherapy, or genetic causes; or with poor egg quality, previously unsuccessful IVF cycles or advanced maternal age. In the egg donor process, eggs are retrieved from a donor's ovaries, fertilised in the laboratory with the sperm from the recipient's partner, and the resulting healthy embryos are returned to the recipient's uterus.
Ovulation induction with IUI: The goal with ovulation induction is to recruit and develop a single egg during the stimulation phase. At the time of ovulation, insemination occurs, placing the sperm directly into the uterus. IUI puts the sperm closer to the egg than possible with intercourse alone. You will come into the office for three to five monitoring appointments to track egg development and cycle timing.
Twenty-eight days is the average length of a menstrual cycle, though anything between 21 and 35 days is considered normal. Fluctuating a little from month to month is one thing, but if your period is so irregular that you don’t even try to track it anymore, it could indicate a problem producing eggs, or ovulating. Ovulation disorders (meaning you ovulate infrequently or not at all) account for infertility in about 25 percent of infertile couples, according to the Mayo Clinic. One of the most common causes of female infertility is polycystic ovarian syndrome (PCOS)—a condition characterized by longer than normal stretches between periods, or even skipping cycles for months in a row. (Get the silent signs of PCOS here.) Irregular periods may also result from excessive physical or emotional stress, which can mess with the hormones responsible for stimulating ovulation each month; being too heavy or too thin, or gaining or losing a lot of weight quickly may also have the same effect. Talk to your doctor; he may be able to prescribe fertility drugs to help induce or stimulate ovulation.

The live birth rate is the percentage of all IVF cycles that lead to a live birth. This rate does not include miscarriage or stillbirth; multiple-order births, such as twins and triplets, are counted as one pregnancy. A 2017 summary compiled by the Society for Assisted Reproductive Technology (SART) which reports the average IVF success rates in the United States per age group using non-donor eggs compiled the following data:[10]


Anger, sadness, and anxiety are common among parents struggling to expand their family. "Having a child already doesn't make going through infertility any easier," says Alice D. Domar, Ph.D., executive director of the Domar Center for Mind/Body Health, in Waltham, Massachusetts, and author of Conquering Infertility. Meeting with a mental-health professional or seeking out blogs and online groups for secondary infertility can help. The website of  the National Infertility Association, resolve.org, is a good place to start.
Once the medications take their effect, your doctor will use a transvaginal ultrasound to guide a needle through the back wall of your vagina, up to your ovaries. She will then use the needle to aspirate the follicle, or gently suck the fluid and oocyte from the follicle into the needle. There is one oocyte per follicle. These oocytes will be transferred to the embryology lab for fertilization.
The number to be transferred depends on the number available, the age of the woman and other health and diagnostic factors. In countries such as Canada, the UK, Australia and New Zealand, a maximum of two embryos are transferred except in unusual circumstances. In the UK and according to HFEA regulations, a woman over 40 may have up to three embryos transferred, whereas in the US, there is no legal limit on the number of embryos which may be transferred, although medical associations have provided practice guidelines. Most clinics and country regulatory bodies seek to minimise the risk of multiple pregnancy, as it is not uncommon for multiple embryos to implant if multiple embryos are transferred. Embryos are transferred to the patient's uterus through a thin, plastic catheter, which goes through her vagina and cervix. Several embryos may be passed into the uterus to improve chances of implantation and pregnancy.

Studies have indicated that IVF mothers show greater emotional involvement with their child, and they enjoy motherhood more than mothers by natural conception. Similarly, studies have indicated that IVF father's express more warmth and emotional involvement than fathers by adoption and natural conception and enjoy fatherhood more. Some IVF parents become overly involved with their children.[136]
Headaches and mood swings: Headaches and mood swings are common IVF treatment side effects. Over-the-counter medications can ease headaches, and while no medication can help with mood swings, knowing that they’re a normal part of IVF treatment helps. If you find mood swings are disrupting your day, be sure to seek out self-care practices such as enjoying alone time, reading a book, taking a nice bath, or sharing feelings with a friend or loved one.
Women who switch from IUI to IVF sooner or begin with IVF get pregnant quicker than those who stick or start with IUI. One study found that undergoing immediate IVF resulted in superior pregnancy rates with fewer treatment cycles compared to those who did two rounds of IUI before switching to IVF.  While the immediate IVF group got pregnant quicker, the overall success after up to 6 IVF cycles was similar.
While it’s always recommended to consult with a medical provider before making any treatment decisions, this article serves as a great jumping point for those looking to get pregnant using assisted reproductive technologies (ART). In it, we discuss everything you need to know about IUI and IVF.  We start things off with a high-level overview, then jump into the different types of each treatment, discuss treatment details, key decisions within each treatment, success rates, cost comparisons, risks, and who each treatment might be a good fit for.
Heavy, as in a pad and a tampon still doesn’t feel like enough. Certain medical conditions, like thyroid problems or kidney disease, can cause excessive menstrual bleeding, medications (such as anti-inflammatory drugs or anti-coagulants) may as well; or the reason may be a condition linked to infertility. In a normal menstrual cycle, the hormones estrogen and progesterone work together to regulate the buildup of the lining of the uterus—that’s the stuff that sheds during your period. But if, for example, your ovaries don’t release an egg, the dominoes are tipped: your body produces less progesterone, hormones become imbalanced, the lining in your uterus over-develops, and you end up bleeding extra heavily. Fibroids in your uterus can also cause heavier or longer-than-normal periods; some types of these benign tumors can block fallopian tubes or interfere with the implantation of a fertilized egg. Up to 10 percent of infertile women have fibroids, according to the American Society for Reproductive Medicine. If you soak through at least one pad or tampon an hour for more than a few hours, see your doctor.  This is the worst health advice gynecologists have ever heard.
The consequences of infertility are manifold and can include societal repercussions and personal suffering. Advances in assisted reproductive technologies, such as IVF, can offer hope to many couples where treatment is available, although barriers exist in terms of medical coverage and affordability. The medicalization of infertility has unwittingly led to a disregard for the emotional responses that couples experience, which include distress, loss of control, stigmatization, and a disruption in the developmental trajectory of adulthood.[15] One of the main challenges in assessing the distress levels in women with infertility is the accuracy of self-report measures. It is possible that women “fake good” in order to appear mentally healthier than they are. It is also possible that women feel a sense of hopefulness/increased optimism prior to initiating infertility treatment, which is when most assessments of distress are collected. Some early studies concluded that infertile women did not report any significant differences in symptoms of anxiety and depression than fertile women. The further into treatment a patient goes, the more often they display symptoms of depression and anxiety. Patients with one treatment failure had significantly higher levels of anxiety, and patients with two failures experienced more depression when compared with those without a history of treatment. However, it has also been shown that the more depressed the infertile woman, the less likely she is to start infertility treatment and the more likely she is to drop out after only one cycle. Researchers have also shown that despite a good prognosis and having the finances available to pay for treatment, discontinuation is most often due to psychological reasons.[16]

^ Lasa, JS; Zubiaurre, I; Soifer, LO (2014). "Risk of infertility in patients with celiac disease: a meta-analysis of observational studies". Arq Gastroenterol. 51 (2): 144–50. doi:10.1590/S0004-28032014000200014. PMID 25003268. Undiagnosed celiac disease is a risk factor for infertility. Women seeking medical advice for this particular condition should be screened for celiac disease. Adoption of a gluten-free diet could have a positive impact on fertility in this group of patients.(...)According to our results, non-diagnosed untreated CD constitutes a risk factor significantly associated with infertility in women. When comparing studies that enrolled patients previously diagnosed with CD, this association is not as evident as in the former context. This could be related to the effect that adoption of a gluten-free diet (GFD) may have on this particular health issue.

The take home message of these studies is that when gonadotropins are given to this patient population at a dose that doesn’t put the patient at significant risk of twins (like the 75 units in the Huang study), they are no better than oral medications (clomid and letrozole) at producing successful pregnancies. This is important because clomid and letrozole are also cheaper to purchase (hundreds vs. thousands of dollars) and easier to administer (oral rather than injectable). For this reason, many clinics have moved away from using gonadotropins in IUI cycles.


Secondary infertility is similar to other types of infertility and shares many of the same signs. However, in secondary infertility you’re unable to conceive or carry a baby to full-term after having a previous successful pregnancy. Infertility can be caused by either the man or woman. Treatment options can include medications to induce ovulation, in vitro fertilization (IVF) or surgery.
Success rates vary with the number of embryos transferred. However, transferring more and more embryos at one time does not increase the chance of live birth significantly, but may only increase the risk of a multiple pregnancy, and its associated risks. The impact of the number of embryos that are transferred also varies with the age of the woman.  
^ GBD 2015 Disease and Injury Incidence and Prevalence, Collaborators. (8 October 2016). "Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015". Lancet. 388 (10053): 1545–1602. doi:10.1016/S0140-6736(16)31678-6. PMC 5055577. PMID 27733282.
In humans, infertility is the inability to become pregnant after one year of intercourse without contraception involving a male and female partner.[2] There are many causes of infertility, including some that medical intervention can treat.[3] Estimates from 1997 suggest that worldwide about five percent of all heterosexual couples have an unresolved problem with infertility. Many more couples, however, experience involuntary childlessness for at least one year: estimates range from 12% to 28%.[4] Male infertility is responsible for 20–30% of infertility cases, while 20–35% are due to female infertility, and 25–40% are due to combined problems in both parts.[2][5] In 10–20% of cases, no cause is found.[5] The most common cause of female infertility is ovulatory problems, which generally manifest themselves by sparse or absent menstrual periods.[6] Male infertility is most commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity.[7] 
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