Programmed Frozen Embryo Transfer in the Absence of Corpus Luteum: Impact on Maternal Cardiovascular Adaptation, Endothelial Function and Risk of Preeclampsia

Programmed frozen embryo transfer (FET) cycles are an integral part of assisted reproductive technologies (ARTs). They rely exclusively on the administration of exogenous estrogens and progesterone to prepare the endometrium, and they are characterized by the absence of a functional corpus luteum (CL). Pregnancies resulting from FET cycles have been associated with an increased risk of complications related to placental dysfunction, such as preeclampsia and fetal growth restriction (FGR). Besides progesterone production, the CL secretes vasoactive and angiogenic factors essential for the regulatory mechanisms that occur during the early stages of pregnancy. Its absence results in a different endocrine environment, which may be associated with differences in normal maternal cardiovascular remodeling. In pregnant women without CL function, reduced vasodilation, increased systemic vascular resistance, altered cardiac output, and inadequate renal adaptation have been reported. In addition, disturbances in angiogenic balance and trophoblast invasion may contribute to abnormal placentation and the development of preeclampsia. Accordingly, the absence of the CL in programmed FET cycles may represent a critical endocrine disorder, predisposing patients to maternal cardiovascular disturbance and adverse obstetric outcomes. Recognition of this potential endocrine and vascular interaction has important implications for cycle selection, risk stratification, and preventive strategies in the implementation of assisted reproduction protocols.