Islam is against population planning (Family Planning) in majority of cases and abortion is strictly prohibited in Islam. This has been mentioned in the Holy Quran as follows:
Indeed lost are they who have killed their children, from folly, without knowledge, and have forbidden that which Allâh has provided for them, inventing a lie against Allâh. They have indeed gone astray and were not guided. (Al-An'am 6:140)
The only valid reason for population planning is the health of the mother otherwise its Haram. If the woman is unable to face the hardship of the process or her life is in danger than she can go for population planning.
Many people are indulged in population planning due to the wrong thinking that they will not be able to feed their children. They must bear in mind that provision of human beings is only in Hands of Allah swt as mentioned in Holy Quran as follows:
kill not your children because of poverty - We provide sustenance for you and for them; (Al-An'am 6:151)
So if you are a Muslims and doing Family Planning you are going against order of Allah SWT.
Here is view of famous Scholar Dr Zakir Naik on the issue of Family Planning: