Infertility Causes

A common misconception is that getting pregnant is a simple task. In reality, trying to conceive can be a long and difficult road for some couples. When you and your partner decide it's time to expand your family, how long should you realistically expect to try before you get pregnant? And at what point is it worthwhile seeing a fertility expert?

How Long Should it Take to Get Pregnant?

Some couples are content to stop their contraception and just see what happens; others find themselves in a monthly cycle of expectation and disappointment. Most GP's won't start fertility investigations or refer you to a specialist until 12 months of trying. The reason for this can be understood when we look at how efficient normal fertility actually is.

Normal Conception Rates

Even for a healthy, fertile couple, the 'per month' success rate is around 15-20%, so it is not at all uncommon for it to take some months to conceive. Overall, around 70% of couples will have conceived by 6 months, 85% by 12 months and 95% will be pregnant after 2 years of trying.
Although for a normally fertile couple, the 'per month' rate is around 20%, as you might expect for couples where there actually is a problem, the pregnancy rate is lower. It is useful to know the overall background rate of pregnancy after any given duration of trying, particularly to make sense of success claims of any treatment. Studies have looked at the ongoing success rates after many years and the results are summarised below:
Number of months trying Overall % of couples having not conceived Monthly success rate (%) Proportion (%) who will conceive in the next 12 months
0 100 20 86
6 30 14 77
12 14 11 69
24 4.3 8 57
36 1.9 6 48
48 1 5 41
60 0.6 4 36
As you can see, 'infertility' is really a poor term to use, because this implies that there is no chance of getting pregnant. For most couples who are referred for further investigations, it would be best described as 'subfertility', meaning reduced fertility, as there is usually a background pregnancy rate - it's just taking longer than they would wish. Of course couples will want to exclude an insurmountable problem, or one which will definitely require some form of treatment, such as fertility drugs, to succeed.

Causes of Infertility

For conception to occur, adequate numbers of actively swimming (motile) sperms need to enter the cervix, work their way up the uterus and into the fallopian tubes. At the same time, an egg must be released from the ovary and be able to make its way down the tube to meet the sperm. The timing for fertility needs to be perfect so that the egg and sperm can combine.  If fertilization occurs, the dividing egg then makes it way back down to the uterus to implant into the thickened lining of the womb. Any problem along the way may result in problems falling pregnant.
The causes of infertility are many and can be due to either issues with female infertility or issues with male infertility, or even a combination of the two.  Some of these common fertility problems are listed below:
  • Ovulation problems 10-15%
  • Tubal blockage or endometriosis 30-40%
  • Male (sperm) problems 30-40%
  • Unexplained 15-20%
These rates are variable for any given population, and are only a guide. Each of these factors is given consideration, in the discussion before, during the examination and in the investigations subsequently arranged.
Other possible causes of infertility are:
For more information on getting pregnant check out our pregnancy videos.
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