Progesterone Intrauterine Device System (IUD or IUS)
The progesterone intrauterine device system (IUD or IUS) releases a progesterone hormone called levonorgestrel into the uterus and prevents pregnancy. Levonorgestrel is a progestogen (progesterone containing hormone) used in a variety of contraceptive products. After the progesterone IUD has been inserted, low doses of levonorgestrel can be administered into the uterine cavity with the intrauterine delivery system.
This IUD has mainly local progestogenic effects in the uterine cavity and studies have suggested several mechanisms that prevent pregnancy:
- Thickening of cervical mucus preventing passage of sperm into the uterus
- Inhibition of sperm capacitation or survival
- Alteration of the endometrium
Ovulation is inhibited in some women using this IUD. In a 1-year study approximately 45% of menstrual cycles were ovulatory and in another study after 4 years 75% of cycles were ovulatory.