This completed observational study evaluated the expression of Hippo-YAP pathway-related genes and proteins and selected microRNAs in maternal blood, placental tissue, and myometrial tissue obtained from women who underwent cesarean delivery at term or preterm gestational ages.

The study compared women with spontaneous preterm delivery and women with term delivery. Maternal blood, placental tissue, and myometrial tissue samples were analyzed using molecular, biochemical, and immunohistochemical methods to explore whether Hippo-YAP pathway activity and related miRNA expression patterns may be associated with the pathophysiology of preterm birth.

Preterm birth remains an important obstetric condition associated with neonatal morbidity and mortality. Although clinical risk factors for preterm birth are well described, the underlying molecular mechanisms are not fully understood. Inflammation, immune regulation, placental function, and myometrial activity are considered important components of the biological processes leading to preterm labor and delivery.

The Hippo-YAP signaling pathway is involved in cellular proliferation, differentiation, tissue homeostasis, immune regulation, and placental biology. Several microRNAs are also known to regulate reproductive tissues, placental function, myometrial activity, and inflammatory pathways. Based on this biological background, this study investigated the Hippo-YAP pathway and selected related microRNAs in maternal blood, placental tissue, and myometrial tissue from women with term and preterm cesarean delivery.

This was a completed observational case-control biomarker study. Participants were not assigned to any intervention. The study included two groups: women who delivered preterm and women who delivered at term. Maternal blood samples were collected before cesarean delivery. Placental tissue samples were obtained after delivery, and myometrial tissue samples were collected from the placental bed during cesarean section. Samples were stored under appropriate laboratory conditions until analysis.

The study evaluated the expression of Hippo-YAP pathway-related genes and proteins, including MST1, LATS1, YAP1, TAZ, MAP4K1, and PIK3C2B, as well as selected related microRNAs, including miRNA-195, miRNA-181c, miRNA-200a, and miRNA-375. Gene and microRNA expression analyses were performed using quantitative real-time polymerase chain reaction. Protein expression was assessed using enzyme-linked immunosorbent assay and immunohistochemistry.

The primary objective was to compare Hippo-YAP pathway-related gene, protein, and microRNA expression patterns between preterm and term delivery groups. Secondary objectives included evaluating expression patterns across maternal blood, placental tissue, and myometrial tissue and exploring whether these molecular differences may contribute to understanding the biological mechanisms involved in preterm birth.

The study was approved by the Sivas Cumhuriyet University Clinical Research Ethics Committee. Written informed consent was obtained from participating women. The project was supported by the Scientific and Technological Research Council of Türkiye (TUBITAK), project number 121S414, and the immunohistochemistry experiments were additionally supported by a complementary research grant, project number T-2022-954-D7.

This study was retrospectively registered after completion of participant enrollment, sample collection, and laboratory analyses for transparency.

Inclusion Criteria:

- cInclusion Criteria:

• Pregnant women aged 18 years or older
• Singleton pregnancy
• Women who underwent cesarean delivery
• For the preterm delivery group: spontaneous preterm labor and delivery between 24 and 34 weeks of gestation
• For the term delivery group: cesarean delivery at term gestational age without active labor
• Written informed consent for participation and collection of maternal blood, placental tissue, and myometrial tissue samples

Exclusion Criteria:

• Multiple pregnancy
• Major fetal anomaly
• Clinical evidence of chorioamnionitis
• Hypertensive disorders of pregnancy
• Diabetes mellitus or gestational diabetes mellitus
• Autoimmune disease
• Chronic inflammatory disease
• Maternal systemic infection
• Placental abruption
• Premature rupture of membranes, if excluded in the original protocol
• Use of medications or presence of maternal conditions that could significantly affect inflammatory, molecular, or placental biomarker expression
• Refusal to provide informed consent

Exclusion Criteria:

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Pregnant women who underwent cesarean delivery at Sivas Cumhuriyet University Faculty of Medicine and were included in either the spontaneous preterm delivery group or the term delivery comparison group.

Individual participant data will not be shared because no prospective data-sharing consent for public individual-level data sharing was obtained, and the dataset includes sensitive maternal clinical information and biological sample-related laboratory data.