Infertility Secondary

The purpose of this study is to evaluate whether progesterone in women with unexplained infertility can increases live birth rate. The main research question is: Does luteal phase support with progesterone increase the live birth rate among couples with unexplained infertility? The study compares progesterone with placebo to determine the effectiveness of progesterone in unexplained infertility. Study participants will: * Perform home ovulation tests and maintain a digital diary to record menstrual cycles and study medication use.10 * Take progesterone or placebo twice daily during the luteal phase of each menstrual cycle for up to six months.11 * Continue usual medical care. No additional hospital visits or invasive procedures are required as part of the study.