An estimated 1 to 13 out of 100 women who use the minipill will get pregnant in the first year of use. The failure rate of the minipill in highly fertile women is higher than that of other hormonal contraceptive methods.

If you become pregnant while taking the minipill, it may be difficult to recognize the signs and symptoms of pregnancy. In addition, if you do conceive there's a slightly higher chance that the pregnancy will be ectopic — when the fertilized egg implants outside the uterus, usually in a fallopian tube.

The minipill won't protect you from sexually transmitted infections, and it may be less effective than combination birth control pills.

Side effects of the minipill may include:

  • Acne
  • Breast tenderness
  • Decreased libido
  • Depression
  • Headache
  • Irregular menstrual bleeding
  • Nausea
  • Ovarian cysts
  • Weight gain
Dec. 01, 2011