All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If the family planning was done for any legal reason, like when the mother is ill or is facing exhaustion due to continuous birth etc., and doctors have ruled that continuous birth may be dangerous for her life or cause harm to her body, then she could use temporary birth control methods to delay pregnancy. But it is prohibited to take any measure, which would permanently stop pregnancy or cause sterility. Jabir narrated: “We used to practice coitus interruptus during the lifetime of the Prophet while the Quran was being revealed.”
For more benefit on permanent birth control, please refer to Fatwa 83837.
Allah knows best.