One of the worst risks of emergency contraception is possible failure leading to ectopic pregnancy. Yes, it can occur, according to Indian researchers from All India Institute of Medical Sciences (1). A case report in 2001 occurred as a result of the use of levonorgestrel (1). For the most part, however, levonorgestrel is considered safe and effective (1).
1. Ghosh B, Dadhwal V, Deka D, Ramesan CK, Mittal S. Ectopic pregnancy following levonorgestrel emergency contraception: a case report. Contraception 2009;79:155-7.