lutueal phase defect (LPD)

A regular cycle is not always a guarantee of normal follicle development and ovulation. The second half of the cycle - the time between ovulation and menstruation - is called the luteal phase. After ovulation, the empty follicle that is left behind transforms into the corpus luteum (yellow body). This corpus luteum produces the hormone progesterone, which plays an essential role in preparing the lining of the womb (uterus) for pregnancy. If it becomes apparent that not enough of this hormone is being produced, or if the luteal phase is too short, then luteal phase insufficiency (LI) is said to occur. The role of LI in a spontaneous cycle as a cause of subfertility is debatable. Although there is insufficient hard evidence regarding the effect of therapy, it is still often applied.