Intra-Uterine System

The term IUS is used to distinguish the hormonal intrauterine contraceptive from copper-based intrauterine devices (IUDs). The IUS is used both as a method of contraception as well as a treatment heavy periods, very painful periods and endometriosis.

The IUS has a plastic T-shaped frame similar to the copper IUD, but with a steroid reservoir. The device is 32mm in length and 4.8mm in diameter. It is inserted through the cervical canal into the uterus, where it sits releasing the hormone 24 hrs a day for a recommended duration of use of 5 years. The amount of synthetic hormone delivered by the IUS is only a fraction of the daily dose received through oral contraceptives, so the side effects should be smaller with the IUS than with oral methods. The IUS can only be fitted by a qualified medical practitioner. During the procedure, which only lasts a few minutes, the cervix is dilated and the IUS is fitted using an insertion device. Removal of the IUS is the same as removing an IUD, and fertility returns immediately.

The IUS prevents pregnancy by the suppression of the endometrium, making it unfavourable to implantation. In some women the IUS reduces ovarian function. It also causes the cervical mucus to thicken, making it impenetrable to sperm.


The IUS has a mean failure rate of less than 0.2 per 100 women years for up to 5 years.



  • Total absence of menstrual periods
  • Irregular bleeding
  • Dilatation of cervix is required which is uncomfortable, and for some women painful
  • Expulsion of the IUS
  • Perforation of the uterus, bowel or bladder
  • Malposition of the IUS
  • Pregnancy causing expulsion, perforation, or malposition
  • Slightly increased risk of ectopic pregnancy if there is an IUS failure


Side effects

  • Some women may develop functional ovarian cysts
  • Breast tenderness
  • Acne
  • Headaches
  • Bloatedness
  • Mood changes
  • Nausea
  • Irregular bleeding
  • Total absence of menstrual period


  • Reduction in heavy and prolonged menstrual periods
  • Reduction in excessive menstrual pain
  • Infrequent or absent menstrual periods
  • High efficacy
  • Reversible
  • Unrelated to sexual intercourse

Absolute contraindications

  • Pregnancy
  • Undiagnosed genital tract bleeding
  • Heart valve replacement
  • Congenital or acquired uterine anomaly which distorts the fundal cavity
  • Suspected or confirmed uterine or cervical malignancy
  • Recent trophoblastic disease
  • Serious side-effect occurring on the COC which are not due to oestrogen
  • Present liver disease, liver adenoma or cancer
  • Present thrombophlebitis or thromboembolic disorder.


Relative contraindications

  • Chronic systemic disease
  • Risk factors for arterial disease
  • Past or present severe arterial disease
  • Severe lipid abnormalities
  • Recurrent cholestatic jaundice
  • Sex steroid-dependent cancer, e.g. breast cancer
  • Functional ovarian cysts which have required hospitalisation
  • Previous ectopic pregnancy.
  • Medicines which may interfere with intrauterine system efficacy (seek a pharmacist’s or doctor’s advice if taking other medications)