The effect of porcine relaxin vaginally applied at human embryo transfer in an in vitro fertilization programme

It has been suggested that the polypeptide hormone relaxin is an early pregnancy factor which facilitates implantation and pregnancy maintenance. To test this hypothesis a double blind randomized placebo controlled trial was conducted where 2 mg purified porcine relaxin or distilled water was given in a vaginal gel on the day of embryo transfer and again 3 days later in a human in vitro fertilization (IVF) programme. There were 96 patients in the randomized trial and 73 patients who were treated concurrently in the same IVF programme acted as a further control group. Of the 51 patients who received relaxin, 10 pregnancies were confirmed and 8 continued successfully. In the 45 patients treated with placebo 10 pregnancies were also confirmed and 6 continued successfully. Amongst the 73 patients concurrently treated outside the trial 14 achieved a pregnancy and 10 continued to term. Thus, porcine relaxin given in these circumstances in a human IVF programme did not appear to improve or interfere with the pregnancy rate. Possible factors that affected the implantation rates in this trial are discussed.