This is as simple as it sounds. Unexplained fertility means that the cause of infertility cannot be explained medically. In situations like this, all the necessary factors needed for conception and pregnancy are favorable, and there is no medical reason why pregnancy shouldn’t occur.
It is usually diagnosed after running a complete fertility evaluation of both the man and woman.
For the woman this means that the fallopian tubes are opened, ovulation occurs normally, good egg quality, normal uterine cavity, and the hormones are balanced. Also, a full semen analysis for the man which shows good sperm count, volume, motility, viscosity, morphology, and pH.
Unexplained infertility can only be diagnosed after all of the above tests have been taken, and there is still no identifiable reason for infertility.
There is no treatment or medication for it. All you have to do is wait and be hopeful.