There could be two possibilities of going for the desired gender of a baby: before it is conceived in the womb of mothers and afterwards.

As regards the former possibility, I think it is undesirable in Islam.

As for changing the gender of the fetus, I think it is Haram, because it amounts to changing the creation of the Almighty. The Qur’ān tells us that it is Satan who advises humans to change Allāh’s creation:

“(Satan said to the Almighty)’I will create in them false desires and order them to slit the ears of cattle. I will order them to tamper with Allāh’s creation.’ Therefore, whoever takes Satan as a guardian instead of Allāh, has indeed become a clear-cut loser.”(4:119)

I believe that choosing the gender of one’s child even before conception is undesirable because we should let the Almighty decide about matters that are of His concern. In China, the state law prevents parents from having more than one or two children, depending upon whether they are living in villages or cities. The result of the implementation of this policy is that Chinese parents frequently get their female babies aborted on learning about her sex through ultra-sound examination. This has resulted in gender imbalance in the Chinese society giving way to frequently reported cases of incest and sodomy.

Allāh Almighty indeed is the best judge: “Is not Allāh the best of all Judges?”(95:8)