Cengiz, MuratYilmaz, Ercan2026-04-042026-04-0420260932-00671432-0711https://doi.org/10.1007/s00404-026-08342-1https://hdl.handle.net/11616/109898Purpose: To evaluate the association between ultrasonographically measured umbilical coiling index (UCI) at 18-24 weeks of gestation and adverse perinatal outcomes in primigravid pregnancies. Methods: This prospective study included 461 primigravid women with singleton pregnancies. UCI was measured at 3 cord segments and classified as hypocoiled (< 0.20), normocoiled (0.20-0.40), or hypercoiled (> 0.40) using percentile distribution and ROC-derived thresholds. Maternal characteristics, delivery outcomes, fetal well-being, placental measurements, cord blood gas values, and neonatal outcomes were compared using Kruskal-Wallis, Mann-Whitney U, and chi-square tests (p < 0.05 was significant). Results: Of the 461 patients, 72 (15.6%) were hypocoiled, 244 (52.9%) normocoiled, and 145 (31.5%) hypercoiled. No significant differences were found in maternal age, BMI, gestational age at delivery, hypertension, diabetes, or placental abruption. Birth weight was lowest in the hypocoiled group (p < 0.001). Umbilical artery pH was significantly lower in the hypercoiled group (p < 0.001). Both hypo and hypercoiled groups showed significantly reduced placental weight/thickness (p < 0.001) and higher rates of non-reassuring non-stress tests (34.7 and 28.3% vs. 9.0%, p < 0.001). Meconium-stained amniotic fluid (p = 0.003), oligohydramnios (p < 0.001), and intrauterine growth restriction (p < 0.001) were more common in abnormal coiling groups. Five-minute Apgar scores were significantly lower in both abnormal groups (p < 0.001). No association was found with fetal death (p = 0.575). Conclusion: Both decreased and excessive umbilical cord coiling in the second trimester are associated with impaired fetal growth and adverse perinatal outcomes. Routine second-trimester UCI assessment may help identify high-risk pregnancies.eninfo:eu-repo/semantics/openAccessUmblical cordUltrasonographyPrenatalPrimigravidaPlacentaScreeningArticle31314163929010.1007/s00404-026-08342-12-s2.0-105029282275Q2WOS:001681249900001Q2