The guidance is based on the following considerations:
•The likelihood of pregnancy is not constant and can vary with changes in a woman’s circumstances during treatment.
•Pregnancy tests may not detect an early pregnancy that has occurred after unprotected sex in the preceding 3 weeks.
•Modern contraceptive methods have low failure rates (0.03–0.6%) when used reliably and consistently but failure rates are substantially higher for some methods because of user error or interactions with concomitant medicines.
•Choice of contraceptive method is an individual one and can depend on a number of clinical factors as well as the woman’s personal preference.