Give scientific reasons : Pregnancy can be stopped / prevented without artificial method of family planning.

For pregnancy days between $10$ to $17$ of menstruation are considered proper. During these days maximum possibility of ovulation / formation of egg process is seen. If a couple avoids coitus during these days then there is no possibility of pregnancy. Similarly the female who are into breast feeding, no egg formation or menstruation cycle is seen. During this time family planning can be done by natural method.