Usual causes of infertility
According to statistical data provided by HFEA (Human Fertilisation & Embryology Authority, the authority that controls the function of assisted reproduction units) in the UK, the reasons that lead couples to fertility treatments are (2008 data):
Male infertility: 29.8%
Female infertility: 28.0%
Multiple causes (both male and female):10.3%
The remaining percentage is attributed to unexplained infertility.
The most common causes for female infertility are:
Hormonal imbalance, no ovulation, damaged or obstructed tubes, endometriosis, insufficient vaginal mucus, no embryo implantation, fibroids, premature menopause, polycystic ovary syndrome, adhesion due to prior surgery or infection of the reproductive organs (pelvic inflammatory disease, PID), which might be caused by sexually transmitted diseases (Chlamydia, gonorrhea).
The most common causes of male infertility are:
Low sperm count (less than 20 million spermatozoa per ml of sperm), low sperm volume (due to obstruction), low motility (spermatozoa cannot ‘swim’ towards the egg), abnormal morphology (the sperm cannot fertilise the egg), no sperm (azoospermia), no ejaculation.
It is quite common that both the man and the woman have a minor fertility issue each. These fertility issues should not cause infertility on their own (the man and the woman are basically fertile), but the combination of them both results in infertility (additive effect). This is called the couple’s combined fertility. In any case, luck is another factor.