Infertility is the inability to conceive after one year of unprotected intercourse in a couple less than 30 yrs of age. If the couple is more than 35 yrs (female) then they should seek help after six months of unprotected intercourse.
Infertility is primary as well as secondary. In primary infertility, a couple has never conceived before but in a case of secondary infertility couple has conceived before but is unable to conceive now.
There are various factors which cause infertility. These can be the male factor, female factor, both male and female, unexplained.