In the UK, 3.5 million couples –about one in six – struggle to conceive and turn to fertility clinics for help and advice. For them, the journey to parenthood will often be long and tortuous, and they may go through many tests to find out what is wrong.
While most of them get a fertility diagnosis quickly and can then go on to decide with their doctors what treatment they want to try, about 20% get a result they might find deeply frustrating – they are told they have "unexplained infertility". None of the fertility tests they have done can successfully explain why they are not able to get pregnant.
IBTimes UK takes a look at what it really means for couples to be given a diagnosis of unexplained infertility and what options they have from this point onward.
What is 'normal'?
Understanding human fertility is complex, because a lot of subtle factors can come into play and influence people's chances of having a baby. The age of the woman, and to a lesser extent, of a man, can have an impact, as well as how stressed they are and what type of lifestyle they have.
Most of the scientific literature suggests that 95% of women under the age of 35 conceive within two years. For a young couple who has been trying for a shorter period of time, with regular unprotected intercourse, it is most likely only a question of time before they get pregnant, and they should not worry too much about infertility.
"For women who are older than 40, it will potentially take longer to conceive but this is an age-related phenomenon, it is not an unexplained problem. Up to 70% of those who have normal investigations may become pregnant within two years," Dr Jane Stewart, consultant in reproductive medicine at the Newcastle Fertility Centre (NHS), told IBTimes UK, at the London Fertility Show.
In other words, being over 40 therefore doesn't mean a woman cannot become mother, it is just that it might take longer to do so naturally. "If we look at babies being born before the widespread introduction of contraception, we see that women in their 40's had less babies than their younger peers, but they did have babies", says Dimitrios Nikolaou, lead clinician at Chelsea and Westminster NHS Hospital's Assisted Conception Unit.
A frustrating diagnosis
Couples who are concerned can nevertheless take fertility tests without waiting two years. This is particularly recommended if the couple is older than 40, but also if there is a medical history suggestive of a problem. For most couples, NICE guidelines advise starting investigations after one year of regular unprotected sex.
A range of tests can be done to assess the most common factors of female and male infertility –usually these are problems with ovulation or with the fallopian tubes for women, and problems with sperm production and quality for men. The most common and accurate tests are analysis of semen samples, blood tests to check women's hormone levels and ovulation, and ultrasound scans to check the state of the ovaries and fallopian tubes.
"If I'm trying to estimate what the causes of infertility are for a couple, I want to know whether the woman is ovulating, whether her tubes are fine, whether he is producing sperm, and at what level. I want to know their age, how long they have been trying for and whether they have had regular intercourse during that time. With that information I can get a pretty good idea of what their chances are of conceiving on their own, what is going wrong and what I can do about it", Stewart says.
If the tests results are all fine, and the couple has tried regularly for a baby for more than two years without success, then the diagnosis of unexplained infertility is given. The clinician can then discuss treatment options.
"I wouldn't give a couple a label of unexplained infertility before they have tried for two years. If their test results are normal before the end of these two years, in my view the best option is to let them go and ask them come back later if they are still struggling," Stewart says.
"I explain to them they are 'normal' and that this is a positive thing. The problem is people usually want a solution quickly and can be frustrated if we don't find anything to tell them after the tests. They don't necessarily want to wait two years, and as doctors we have to be understanding but firm because we don't want to risk intervening medically too early when they could have had a baby naturally".
In need of a solution
When couples do end up receiving a diagnosis of unexplained infertility, they can go down the route of treatments, just like couples who have been told the cause of their infertility.
In-vitro fertilisation (IVF) is considered the most interesting approach because it bypasses a lot of the smaller, more subtle problems, and can give doctors clues about what is causing the infertility. The success rate of IVF for couples with unexplained infertility is as high as that of other infertile couples.
"IVF is the option I tend to go with because it allows me to see how the woman's ovaries respond to the drugs and whether the sperm functions properly at the time of fertilisation; Subtle problems with the fallopian tubes are by-passed. For example I recently met a couple who had had unexplained infertility for three years, and who realised by going through IVF what the problem was – scientists saw in the lab that there was no sperm-egg binding," Stewart explains.
At the other end of the spectrum from fertility treatments is the "expectant management" approach. Couples with unexplained infertility may choose to keep trying on their own, and to be closely followed-up by doctors. In some situations, treatment may not be a suitable option for example when the woman is older or has a very low ovarian reserve. Expectant management may then be the most appropriate strategy.
"Again, this may be difficult for patients to hear, as they are frustrated with their diagnosis of unexplained infertility. It is understandable but it is also worth remembering that most of these couples are not entirely infertile – rather we can talk of 'subfertility'. They can conceive naturally, it just is less likely they will do so. But for some of them, waiting and trying without fertility treatments – which can be invasive – does remain the best alternative possible," Stewart concludes.