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What is infertility What does it mean to have a fertility problem? That may seem like a very silly question, but it is more difficult to define fertility and infertility than you might at first imagine. Clearly, it must mean that you are having difficulty getting pregnant, but how long do you need to try for before it is established that there is a problem? Most couples will not achieve a pregnancy in their first month of trying, no matter how “fertile” they may be. How many months should you try before it is decided that there is a problem? The original medical definition of infertility was “a failure to achieve a pregnancy after twelve months of regular, unprotected intercourse”. But what about the couples who get pregnant in the thirteenth month? Are they infertile? Clearly not. Infertility is not a clear-cut symptom in the way that chest pain or shortness of breath is. Many people tend to think of fertility as an "all-or-none" phenomenon; you are either fertile, or you are infertile. Perhaps one of the most important messages I can leave you with is to try to understand the concept that there are different degrees of fertility and infertility. We all understand what it means to be truly infertile. It means a complete inability to be become pregnant, irrespective of however long the couple try. Only a very small proportion of the couples I am asked to see are truly infertile, however. Most have reduced or impaired fertility. It is very important to understand that we, as human beings, are not as fertile a species as we sometimes care to imagine. Our natural chance of conception per cycle (what we call our fecundability) is lower than many people imagine. Right across our community, the figure is said to be approximately 20%, although it is certainly higher than this for young people, and much lower as we get older. It is possible to draw up a pregnancy graph showing how pregnancies happen over time, assuming a constant fecundability of 20%. If 20% achieve a pregnancy in their first cycle, eighty couples will remain who are still not be pregnant after the first cycle. In the second month, 20% of that eighty will achieve a pregnancy, leaving sixty couples still not pregnant at the end of the second cycle, and so forth. This is what that graph looks like over time.
There are a couple of really important things to note with this graph:
Modern studies have certainly now shown that we have previously underestimated our fertility, however, especially with young people. It is now recognised these couples have a much higher fecundability (chance of conception per cycle) of 33-40%. Figure 2 is a similar pregnancy graph, but it is now based on a fecundability of 40%.
Two things are immediately obvious in this graph:
We now realise that younger couples can be said to have impaired fertility after six months of trying, not twelve. Finally, let’s look at a pregnancy graph for a group of couples who have significant fertility problems because of one or more medical issues. These couples have a fecundability of, for arguments sake, 5% (Fig. 3). Their pregnancy graph is strikingly different):
The message that comes from all of this is that fertility is a more variable thing than we might have imagined. Very few couples are completely infertile (a fecundability of 0%), or completely fertile (a fecundability of 100%). Some couples are naturally more fertile than others. The same couple, at different stages of their lives, will have a markedly different level of fertility. These are really important concepts when it comes time to consider the difficult question whether it is time to investigate and/or treat a suspected fertility problem. What factors affect fertility? Fertility problems are much more common that we think. One couple in six may experience some difficulty in conceiving, and one in twelve will experience a significant difficulty. In about 40% of cases the problem will be predominantly with the male, and 40% predominantly with the female. In about 20% we will struggle to find a clear explanation for the couple’s difficulties. In many cases, it will not be one single factor, but two or more factors which have combined together to markedly reduce a couple’s fertility. These factors might individually be relatively minor, but combined together, they may reduce a couple’s fecundability from 20% to 5% or less. Length of time you have tried to conceive It is hardly surprising to learn that the longer you try to become pregnant without success, the less your future chance of becoming pregnant naturally. If your natural fecundability is 20% when you first start trying, after 12 months without success your chance of conception will have dropped to about 10% per cycle. After two years, the chance of conception per cycle will be ~ 5%. After three years, the odds have fallen to about 2-3% per cycle. Age Age has a profound effect on our natural fertility. This applies both to the man and the woman, but is particularly so for the woman. This natural decline in fertility for the woman begins after the age of thirty and the rate of decline becomes more marked after her mid-thirties. This is a biological fact of life that many in the community are finding very difficult to accept. It occurs even in the presence of regular ovulation cycles. It is true that it is the biological age of your ovaries, not necessarily the number of years since your birth, which will determine your natural fertility. Some women at 41 will have retained more healthy eggs than another women at 37. Across our community, however, this marked effect which age has on our fertility cannot be denied. We all know someone who had a baby at 44 or 45. What we forget, however, is that the odds of this occurring are very small indeed. Obesity There is now clear evidence that obesity reduces your natural fertility. Obesity significantly increases the risk of having irregular, non-ovulation cycles. Even in the woman has regular ovulation cycles, however, obesity has been shown to reduce her natural fertility. If the woman’s partner is also obese, that couple’s fertility is further reduced. Smoking Smoking also appears to have an effect on fertility, especially female fertility. Some studies have shown that women who smoke are more likely to reach the menopause early. There is something in cigarettes that appears to be toxic to your ovaries. Some studies have shown that “time to conception” (ie degree of fertility) is reduced in women who smoke heavily. Success rates in IVF treatment may also be reduced in women who smoke heavily. So, if you want to get pregnant, don’t leave it too late, don’t be obese, and don’t smoke! When do I consider investigating a suspected fertility problem? There is no simple answer to this question and every couple’s circumstances will need to be considered separately. As a general rule however, I certainly believe that a couple should start investigations after 12 months without success, at the very latest. As discussed previously, there is now very good reason to believe that young couples less than thirty years of age can be considered to have a potential fertility problem after six months without becoming pregnant. They should give serious consideration to some basic investigations at that time. At the opposite end of the spectrum, older couples should also consider early investigation. Their natural fecundability will, of course, be lower at this stage of their lives. It would not surprise us, therefore, to find that a couple in this age group may not have achieved a pregnancy after 6-9 months. However, the dilemma for these couples is that their biological clocks are ticking fast. They may not have time to wait for 18 months, discover that there definitely is a fertility problem, and then try and resolve it. When do I consider treating an infertility problem? There are no hard and fast rules and every couple’s situation will need to be considered separately. There are four important questions that I will ask myself every time I see a couple with fertility problems:
Age is clearly an important issue, especially at both ends of the age spectrum. Older couples may simply not have time to wait very long before commencing treatment. Younger couples do have time on their side but are much more likely to have a serious fertility problem if pregnancy does not occur naturally. They are also likely to respond extremely well to fertility treatments. A diagnosis often helps us make a decision. It may help me to decide what the couple’s chance of natural conception will be over time. If no abnormality has been found we might be more tempted to defer treatment for a little longer. If a severe abnormality is found, however, such that the couple’s fecundability is assessed to be extremely low then there is hardly any point in deferring treatment, regardless of age or how long they have tried. The duration of a couple’s fertility problems is clearly also a key factor. We know that when a couple have tried for two years without success their fecundability has fallen to 5%. After three years, it is 2-3%. Some of our infertility treatments, such as IVF, are not necessarily miracle solutions or “guarantees” of success. However, they can offer some couples a chance of conception, per cycle, of >30%. They have the potential to offer a couple a vastly increased chance of becoming pregnant per cycle. The likelihood that treatment will be successful must always be considered. Modern artificial reproductive technologies have become remarkably successful for many different types of fertility problems. Perhaps the one key exception to this is age-related fertility problems. Around the world, no-one has yet found a really good solution to this difficult problem. |
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