Serum Progesterone and Threatened Abortion During Lactation

This study aims to evaluate the effect of first-trimester maternal serum progesterone levels on threatened abortion in women who conceive during the lactation period. Serum progesterone concentrations will be measured in lactating pregnant women during the first trimester, and their association with the etiology of threatened abortion will be analyzed. Threatened abortion is defined as vaginal bleeding occurring in the first trimester of pregnancy and represents a risk for early pregnancy loss. Previous studies have shown that serum progesterone levels may be lower in cases of threatened abortion compared to healthy pregnancies and play an essential role in predicting miscarriage risk. Serum progesterone is therefore considered a useful biomarker for assessing pregnancy viability and prognosis. During lactation, progesterone levels may vary depending on breastfeeding duration and maternal hormonal status, and generally remain low, similar to follicular-phase levels in non-pregnant women. However, normal reference values during lactation are not well established. This study aims to contribute new data to the limited literature on the relationship between lactation, serum progesterone levels, and threatened abortion, and to provide insights that may help improve early pregnancy loss prevention strategies.