Sterilization operations are not permitted. They are considered as altering the creation of Allah.
“He said: ‘I will overtake an appointed portion of your men in any case. I shall lead them astray and engross them in vain desires. I shall inspire them and they will cut off the ears of the cattle and they will alter Allah’s creation.’ Whoever adopts the strayed ones as an authority before Allah will certainly suffer a manifest loss.” (4:118-119)