Does progesterone support in luteal phase deficiency help subfertile couples achieve a pregnancy?

This study is testing whether progesterone supplements taken in the second half of the menstrual cycle (luteal phase) can help women who have had trouble getting pregnant because of a hormonal problem called luteal phase deficiency. All women in the study will also learn a natural fertility awareness method called the Sympto-Thermal Method to track their cycles. Researchers hope this treatment will increase the chances of pregnancy. You may be eligible if: - You are a woman aged 18 or older - You have been diagnosed with a luteal phase hormonal defect based on hormone blood tests - You have been trying to get pregnant for 12 months without success, OR have had 3 or more miscarriages You may NOT be eligible if: - Your infertility is due to blocked tubes (confirmed by testing) - Your infertility is due to a male factor (abnormal sperm analysis) - You are exclusively breastfeeding - You are currently using contraception - You are currently pregnant - You are currently taking fertility medications or supplements (including Vitex agnus) Talk to your doctor about whether this trial might be right for you.