If emergency contraception is only used occasionally, it generally has a minor impact on fertility. However, frequent use of emergency contraceptives may lead to infertility.

Emergency contraception usually consists of a combination of estrogen and progestin, with a high hormonal content. Its primary functions are to alter cervical mucus viscosity, hinder sperm mobility, suppress ovulation, and modify the endometrial environment in the uterus, thereby providing a contraceptive effect.

Some may cause menstrual irregularities or ovulation disorders, affecting the motility of the fallopian tubes, potentially leading to ectopic pregnancies, which can cause infertility. Thus, emergency contraception should not be used as a regular method of contraception.