One out of five couples will have difficulty conceiving at some time. Some couples will have conceived a pregnancy together in the past yet will have difficulty in achieving another pregnancy. In other cases, the female may have been pregnant with another individual or the male may have fathered a child with a previous partner.
Fertility problems are becoming more common as couples look to start or grow their families at an older age.
In addition, our lifestyle can impact on the ability to conceive. See 'what else affects fertility'.
However, it is difficult to determine whether there are 'increased causes of infertility' due to facets of modern living.