What is the disadvantages of morning after pill?

No downside to EC: Emergency contraception, such as Plan B (aka morning after pill) is safe and 90% effective in preventing pregnancy. There are very few, if any, disadvantages other than it not being successful in preventing pregnancy.

Possibility of: Side effects. Potential side effects w emergency contraception: tender breasts; menstrual flow changes (spotting, bleeding, early or late period); loose stools; dizziness; headache; nausea/ vomiting; abdominal pain / cramping or fatigue. For chest tightness, difficulty breathing, swelling of lips, mouth, throat – call 911. Take pregnancy test ; notify dr if your period is 7 or > days late.

Getting pregnant: At best the morning after pills are only 50% effective in preventing pregnancy. For overweight patients with BMI 25 or greater Plan B is NOT effective. If you are overweight Ella (ulipristal acetate) is a better choice: while less effective than in normal weight patients it still offers some protection. The most effective emergency contraception is insertion of the copper IUD which is 100 % effective regardless of BMI