"The (WHO) performed a large multinational study to determine gender distribution and infertility etiologies. In 37% of infertile couples, female infertility was the cause; in 35% of couples, both male and female causes were identified; in 8%, there was male factor infertility. ... In the same study, the most common identifiable factors of female infertility are as follows: • : 25% • : 15% • : 12% • Tubal blockage: 11% • Other tubal/uterine abnormalities: 11% • : 7%"