No difference found in pregnancy rates for women using either the LNG-20 intrauterine system (IUS) or intra-uterine device (IUD) for contraception

Reversible methods of contraception include the use of a system or device placed inside the uterus. The IUD is a copper device inserted into the uterus to prevent pregnancy. The intrauterine system (IUS) contains hormones that will be gradually released and provide effective contraception until removed.

The review of trials compared IUDs to IUSs and found there was no difference in the rate of unplanned pregnancies. The review found that a lack of menstrual bleeding is more likely with IUS use and that IUD use is more likely to cause heavy menstrual bleeding and pain.

Authors' conclusions: 

Evidence suggests there is no difference in pregnancy rates among LNG-20 IUS, IUD >250mm2 and Norplant-2 users. The LNG-20 IUS more effectively prevented intrauterine and extrauterine pregnancies than IUDs ≤250mm2. P4-IUS was significantly more effective than non-medicated IUDs, but no difference was observed when compared to IUDs ≤250mm2. Continuation rates for LNG-20 IUS, non-hormonal IUDs and Norplant-2 were similar. Lack of menstrual bleeding was the main reason for discontinuation of LNG-20 IUS.

Recent evidence, from studies meeting the review inclusion criteria for the update conducted in July 2009, suggests that the LNG-20 IUS does not impact upon breastfeeding performance or the growth and development of breastfed infants in lactating women nor did the device have an adverse effect on glucose metabolism among insulin-dependent diabetic women.

Read the full abstract...

Hormonally impregnated intrauterine systems (IUSs) add a progestogen to a non-medicated contraceptive device to improve contraceptive action.


To assess the contraceptive efficacy, tolerability and acceptability of IUSs versus other reversible contraceptive methods.

Search strategy: 

Searched databases, reference lists and relevant individuals/organisations covering the period from 1972 to July 2009.

Selection criteria: 

Randomised controlled trials (RCTs) comparing IUSs with other reversible contraceptives and reporting on pre-determined outcomes, including pregnancy and continuation rates, in women of reproductive years.

Data collection and analysis: 

Two blinded reviewers independently assessed quality and extracted data on events per women months and single decrement life table rates for pregnancy, continuation, adverse events and reasons for discontinuation. Events per total potential number of women at follow-up were collected for hormonal side effects and menstrual change.

Data were pooled at the same points of follow-up to calculate rate ratios and single decrement life table rate differences. Similar interventions were combined and non-hormonal intrauterine devices (IUDs) were divided into three categories: copper IUDs >250mm2, copper IUDs ≤250mm2, and non-medicated IUDs.

Main results: 

Twenty-five RCTs met the inclusion criteria and nine were included in meta-analyses: four comparing LNG-20 IUSs (Mirena®) with non-hormonal IUDs, one with Norplant-2, one with combined oral contraceptives (COCs) and three comparing P4-IUS (Progestasert®) with non-hormonal IUDs.

No significant difference was observed between LNG-20 and IUD >250mm2 or COC user pregnancy rates.  LNG-20 IUS users were significantly less likely to become pregnant than IUD ≤250mm2 users. LNG-20 IUS users were more likely to experience a lack of menstrual bleeding and device expulsion than IUDs >250mm2 users. LNG-20 users were significantly more likely than all IUD users to discontinue because of the lack of menstrual bleeding. They were significantly more likely to experience lack of and infrequent mentrual bleeding, but significantly less likely to experience prolonged bleeding and spotting than Norplant-2 users.

P4-IUS users were significantly less likely to become pregnant and more likely to discontinue than non-medicated IUD users, but no significant difference was observed for P4-IUS versus IUD ≤250mm2 for these two outcomes. P4-IUS users were less likely to expel the device and more likely to discontinue because of menstrual bleeding and pain than IUDs ≤250mm2 users.