Plan B One-Step, the brand name of the medication levonorgestrel, is an emergency contraceptive pill that helps prevent unwanted pregnancy. Women can use Plan B One-Step after a contraceptive failure or unprotected sex, but the medication is a backup method of birth control and is not intended to be used routinely. However, even with limited use, serious side effects may occur. Although these serious side effects are not common, women who experience them should call a doctor immediately.
Allergic Reaction
Women who experience an allergic reaction to Plan B may develop a hive or rash. Itching, tightness in the chest, difficulty breathing and swelling of the face, lips, mouth or tongue may also occur, according to Drugs.com. Women who believe they may be having an allergic reaction should seek immediate medical attention.
Vomiting
Women who vomit within an hour of taking a Plan B tablet may throw up the tablet. Although the vomiting itself isn't dangerous, women may not be protected against pregnancy when this occurs. Women should consult their doctor immediately after vomiting after taking a Plan B tablet for advice on how to proceed.
Severe Abdominal Pain
Experiencing severe abdominal pain after taking Plan B may be a sign that an ectopic pregnancy is developing. Ectopic pregnancies occur when a fertilized egg does not implant inside the wall of the uterus as its supposed to, but implants in the fallopian tube or another undesirable location. When this happens, the fetus may cause serious and life-threatening complications to the mother as it grows. Doctors may use the drug methotrexate or perform surgery to stop the embryo from growing and protect the mother, according to eMedTV.com.
