Why Some Couples Suffer from Subfertility? Subfertility affects one in six couples. While in some cultures the woman is often blamed, in reality research has shown that female factors are responsible for 30% of cases, male factors for a further 30%, and combined male and female factors account for 20%, while the remaining 20% are unexplained. Nature appears to be surprisingly inefficient. The chances of pregnancy occurring in a healthy couple having unprotected intercourse during the fertile time of the cycle are about 25% per month. Statistics show that after about twelve months of trying, approximately 80% of couples will have conceived and the remaining 20% will seek investigation in the hope for a diagnosis for their infertility.