This is basically a companion paper to the one published last year in the British Medical Journal,1 which concentrated on the pill and was comprehensively criticised in the January 2012 issue of this Journal,2 to which readers are referred. This analysis, also from the Danish registry, looks at the Evra® patch, NuvaRing®, Implanon® and the levonorgestrel-releasing intrauterine system (Mirena® IUS). All the previous issues of confounding, lack of information regarding smoking, body mass index and family history, and not comparing like with like, apply here.

It is important to compare new users with new users, as a well-established fact is that the …