1) Ensures a healthy offspring.
2) Prevents STDs. like gonorrhea, syphilis, AIDS etc.
3) Prevents unwanted pregnancies.
4) It ensures that the mother is also in sound health as a pregnancy makes major demands on the mind and body of the mother. 
Two areas which have improved :
1) Better family planning has reduced the family size and consequently the population of the country. 
2) Mortality rates of both mother and child have gone down. 
3) Awareness about contraceptive devices in the society has increased which serves as measure of birth control.