Several hormonal sources for pregnancy loss have been suggested, including untreated thyroid disease, diabetes, polycystic ovarian syndrome (PCOS), and luteal-phase defect.

Thyroid disease is easily diagnosed through blood tests for thyroid-stimulating hormone (TSH) and thyroid hormone itself (free T4). Fortunately, thyroid dysfunction responds promptly to treatment.

Although uncontrolled diabetes may lead to an increased risk of pregnancy loss, individuals with this degree of glucose intolerance usually have been identified prior to the pregnancy.

Women with PCOS may experience an increased risk of first-trimester pregnancy loss. It is estimated that young patients with PCOS have a 25% chance of first trimester pregnancy loss compared with a rate of 10% to 15% in an age-matched control group. The mechanism through which PCOS may increase the chance of pregnancy loss is unknown, but limited preliminary studies suggest that the use of metformin (Glucophage) may reverse this tendency.

Finally, women who produce a suboptimal amount of progesterone, both in the luteal phase and in early pregnancy, are at increased risk for pregnancy loss. However, testing for such luteal-phase defects remains somewhat problematic and controversial. In our practice, we routinely supplement all patients in the first trimester of pregnancy with progesterone suppositories, obviating the need for additional diagnostic tests such as an endometrial biopsy.