Potential Complications. One of the most serious side effects of birth control pills is an ectopic pregnancy. This is when a fertilized egg attaches itself outside of the uterus. These types of pregnancies are very rare. Also, there is a chance of developing a blood clot or a liver tumor. Blood clots increase the risk of heart attacks and strokes. Women who smoke are more at risk for developing blood clots while on the pill. Again, these complications are very rare and should be discussed with a medical professional.
