Female causes of infertility explain around one-third of all cases investigated. Male causes represent around one-third of cases, and a further one third remain unexplained. The good news is that today almost all cases of infertility are amenable to treatment.
IVF was originally developed to by-pass damage to the Fallopian tube. This can be caused by a natural defect or by infection. Blockage in the tube would prevent a sperm cell from making contact with the egg released from the ovary at ovulation. Fertilisation in the laboratory would by-pass the damage - hence the ‘test-tube baby’.
Hormonal disorders - usually in the levels of reproductive hormones like testosterone and estradiol - may cause polycystic ovarian syndrome (PCOS), which is reflected in irregular (or absent) menstrual cycles and hormone levels. IVF treatment, which stimulates the ovary, may raise the risk of ovarian hyperstimulation syndrome (OHSS), so the first option is usually intrauterine insemination with careful ultrasound monitoring.
Endometriosis is a condition in which tissue normally formed in the uterus develops elsewhere in the reproductive tract. This common condition can cause pain and disrupt pregnancy in both natural and assisted reproduction. Surgery may sometimes be necessary.
In many clinics today the most common explanation for infertility is simply female age. Studies have shown that fertility begins to stall after the age of 35, and by the age of 40 is in a steep decline. More and more women are delaying the birth of their first children until home and career are well established - but this is often at the expense of their natural fertility.
The main explanation for age-related infertility is simply the approaching end of a woman’s reproductive life. This ‘ovarian reserve’ - a measure of female fertility during the reproductive years - can be tested by hormone levels and ultrasound.
These tests - like AMH or antral follicle count - will give an idea of remaining fertility, but, once gone, eggs can never be replaced. It is also known that the genetic quality of eggs deteriorates with age, such that embryos become less viable and chromosome disorders more likely.