How does a Levonorgestrel-Releasing IUS Work?

The LNG-IUS exerts a pre-fertilization effect in vivo.

Black D. and Waddington A. et al. Build Your Expertise: IUC slide deck: 63,84.
Costescu D. and Guilbert E. et al. Preceptorship Program on IUC insertion - Module 2
SOGC Clinical Practice Guideline, Canadian Contraception Consensus (part 3): Chapter 7 – Intrauterine Contraception