My rescued cat, Mamma, gave birth to three kittens. They are 2 months old. But the mommy cat is pregnant again. I decided to go for the sterilization but got no time to do that. Will abortion be a good option now? If not, when should I go for her sterilization?

A lot of these decisions depends on what stage of the gestation the mother is in . In very early stages ,ovariohysterectomy may be performed without risk , but progressively it may not be an option . Get an ultrasound scan done to confirm foetal age and then doctors can advise about the safest course of action