1. Introduction
Infertility, infertility
INFERTILITY
Infertility, a problem of the reproductive system defined as the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse,Tacrolimus, also known as FK506, was found as a 23-membered macrolide produced by Tacrolimus is more commonly used for women with infertility in Japan, although it has not yet received regulatory approval for this purpose. The practical management for the use of tacrolimus is currently left at the discretion of individual fertility clinics and doctors. This exploratory clinical trial is conducted to determine the efficacy, safety, and dosage of tacrolimus treatment in women with intractable infertility who failed to achieve a chemical pregnancy after multiple embryo transfer (ET) cycles with morphologically good-quality embryos. The following 2 key selection criteria were set: no underlying factors of infertility despite appropriate evaluation and presence of Th1-dominant immune state, defined as a Th1/Th2 cell ratio ≥ 10.3 in the peripheral blood. In this study, tacrolimus will be administered for 16 days, starting from 2 days before ET, which corresponds to the period before fetal organogenesis.