If you use the physiological method of interrupted sexual intercourse (coitus interruptus), you need to understand the risk of conceiving.

Withdrawal of the penis before ejaculation during intercourse is not an efficient contraceptive method, as the sperm cells do not only release during orgasm but can do so during the intercourse, meaning that the woman can still conceive.

The physiological method of following the calendar is not efficient, as the woman’s cycle can be affected by multiple factors. 

Insufficient contraceptive methods may be used by couples who understand the risks and plan to have the baby in case they would conceive.