1. Contractions of the lower uterine segment during transvaginal ultrasound cervical length: incidence, significance, proper measurement, and management;Berghella;Am J Obstet Gynecol MFM,2024
2. Real-time ultrasound demonstration of uterine isthmus contractions during pregnancy;Farràs;Am J Obstet Gynecol,2024
3. Chapter 34 – Pelvic anatomy and scanning techniques;Hughes,2011