Additional Study Information: The unintended pregnancy rate is rising despite increased availability and use of different types of emergency contraception (EC) pills. Few studies have addressed reasons for EC failure, yet such an investigation may allow researchers to better understand if EC can be used more successfully.Recently studies have shown that EC failure rates are higher in heavier women compared to thin women. No studies describe why these differences exist. We propose a study to compare blood levels in thin and heavier women of two types of EC pills levonorgestrel EC (like Plan-B One Step or its generic counterparts) and ulipristal acetate EC (ellaOne). We hope to show that all women have similar blood hormone levels. If women of all weights have similar blood hormone levels, then we would recommend research to find alternative reasons for observed differences in EC failure between thin and heavier women.