Expression of Progesterone Membrane Receptors in Placentas From Pregnancies Complicated by Intrauterine Growth Restriction: A Prospective Observational Case-Control Study

Intrauterine growth restriction (IUGR) remains one of the leading causes of perinatal morbidity and mortality. Although placental insufficiency is considered the major underlying mechanism, the molecular pathways responsible for impaired fetal growth are not fully understood.

Progesterone is essential for maintaining pregnancy and exerts its biological effects through both classical nuclear receptors and membrane progesterone receptors. Among these, progesterone receptor membrane component-1 (PGRMC1), progesterone receptor membrane component-2 (PGRMC2), and members of the progestin and adipoQ receptor (PAQR) family have recently attracted attention because of their roles in placental development, angiogenesis, immune regulation, and maintenance of placental integrity.

The present study will prospectively recruit women diagnosed with IUGR and healthy pregnant women delivering at the same institution. Placental samples collected immediately after delivery will undergo molecular analysis using quantitative real-time PCR to determine receptor expression levels. Clinical and obstetric characteristics together with neonatal outcomes will be recorded prospectively.

The findings may contribute to a better understanding of the molecular mechanisms underlying placental dysfunction in IUGR and may identify potential biomarkers associated with adverse pregnancy outcomes.

This study was retrospectively registered in ClinicalTrials.gov (NCT07701837). At the time of protocol development, the term intrauterine growth restriction (IUGR) was used to describe pregnancies with suspected impaired fetal growth. Before biomarker analyses, all growth-impaired pregnancies were phenotypically reclassified according to the contemporary Delphi consensus definition and ISUOG Practice Guidelines into fetal growth restriction (FGR) or small for gestational age (SGA). Consecutive participant recruitment continued throughout the approved study period, resulting in a final cohort of 110 singleton pregnancies (48 FGR, 29 SGA, and 33 appropriately grown controls). Comparisons between the FGR and SGA phenotypes were performed as secondary, hypothesis-generating analyses. No changes were made to participant recruitment procedures, biospecimen collection, laboratory methods, or primary biomarker measurements following this phenotypic classification.