A comparative study on the dislocation rate of the Mirena® and the
Multiload 375® intrauterine device
G.S. Merki-Feld, D. Schwarz, P.J. Keller
Department of Gynaecology, Clinic for Endocrinology, University of Zürich,
Switzerland
Introduction: Displacements of intrauterine devices (IUDs) decrease
their effectiveness. While expulsions are mostly noticed by the users,
intrauterine dislocations can occur without causing symptoms. Women with
intrauterine dislocations are at increased risk for pregnancy. In Switzerland
the levonorgestrel – releasing IUD Mirena® (LNG-IUD) has been introduced in
1997. The clinical observation that women with one or two previous expulsions of
a Multiload 375® intrauterine device (ML-IUD) do not expell the LNG-IUD was the
reason for us to investigate, whether the rate of complete or partial expulsions
might be different for this two types of IUDs.
Aims and Methods: In a retrospective cohort study we compared the
number of dislocations in users of the ML-IUD and the LNG-IUD. The data were
compiled from women attending our family planning clinic from 1997–2002. From
a chronological list of IUD insertions we identified all women with a LNG-IUD
and in each of these cases the next woman with an ML-IUD. Only IUD-users with a
sonographic control of the correct IUD location after insertion were comprised.
Altogether 107 women with a LNG-IUD complied with the inclusion criteria.
Vaginalsonography for the control of the correct IUD – location was performed
after insertion, 6 weeks later and thereafter 6 monthly. The observation period
ranged from 6 weeks to 60 months. Parity, hysterometer length and previous IUD
dislocations as possible factors influencing the expulsion rate in both groups
were documented for all women.
Results: Altogether 1882 cycles with a ML-IUD and 1749 cycles with a
LNG-IUD were evaluated. Parity, hysterometer length and the mean observation
interval were not different between the groups. Six weeks after insertion a
dislocation was documented in 11% of the ML-IUD users and 4% of the LNG-IUD
users (p<0.06). Over the whole observation period the dislocation rate
for the ML-IUDs was 29% vs. 18% for the LNG-IUDs (p<0.05). More than
50% of the dislocations occurred within six months after the insertion of the
devices.
Conclusion: The rate of partial and complete expulsions is
significantly lower for the LNG-IUD compared to the ML-IUD. The low rate of
dislocations might contribute to the high safety of the LNG-IUD.
