Lippe's loop is a type of contraceptive used as:

Lippe’s loop is an example of a non-medicated intra-uterine device or IUD used in female contraception.

Lippes loop is a plastic double “s” loop. It attracts the macrophages stimulating them to accumulate in the uterine cavity. Macrophages increase phagocytosis of sperms within the uterus and act as a contraceptive.