According to the American Society for Reproductive Medicine, endometriosis may be classified as stage I (minimal), II (mild), III (moderate), or IV (severe), based on Number, location, and depth of implants Presence of endometriomas and filmy or dense adhesions (see table Stages of Endometriosis) Table The endometriosis fertility index (EFI) has been developed to stage endometriosis-associated infertility; this system can help predict pregnancy rates after various treatments.