The Combined Effect of Magnesium, Palmitoylethanolamide, High-Molecular-weight Hyaluronic Acid, Vitamin B6, and Vitamin D in Preventing Preterm Birth:

Inclusion Criteria: * Signed informed consent Singleton pregnancy Maternal age ≥ 18 years Gestational age between 20+0 and 34+0 weeks at enrollment Cervical length between 15 mm and 30 mm measured by transvaginal ultrasound Exclusion Criteria: * Fetal structural anomalies Maternal chronic diseases or pregnancy-related conditions, including diabetes, hypertension, preeclampsia, cardiovascular disease, infections, or autoimmune disorders Multiple gestation Fetal growth abnormalities (estimated fetal weight \<10th or \>90th percentile) Prelabor rupture of membranes (PROM)