ABSTRACT

Because progesterone was thought to be important for the maintenance of normal pregnancy, the concept that a deficiency in progesterone might lead to miscarriage was a natural follow-on. By the late 1940s, it had been shown that functional reproductive deficits sufficient to cause infertility or recurrent abortion were present in women who appeared to be having regular menstrual cycles.5 These abnormalities were due to a deficit in progesterone secretion during the luteal phase of the cycle (luteal phase deficiency). This disorder was characterized by inadequate endometrial maturation and was reported in up to 60% of women with recurrent miscarriage. However, these early studies are open to question since there was no reliable method of dating the cycle. Since many of these studies presumed that the patient’s menstrual pattern is a normal 28-day cycle, these endometrial abnormalities could be related to prolonged cycles. However, more recent studies on the hormonal cycle have confirmed abnormalities of corpus luteal function with deficiency in progesterone levels in the luteal phase and early pregnancy of those with a history of miscarriage but in a lower percentage.6 In one of the few prospective studies evaluating women with three or more consecutive miscarriages, luteal phase defect (LPD) was believed to be the cause in 17%.7 Those found to have LPD are more likely to have early losses (prior to the detection of fetal heart activity) than later loss.8