Nassr AA, Berghella V, Hessami K, Bibbo C, et al. Intrapartum ultrasound measurement of angle of progression at the onset of the
second stage of labor for prediction of spontaneous vaginal delivery in term
singleton pregnancies: a systematic review and meta-analysis. Am J Obstet Gynecol 2021 Aug 9. pii: S0002-9378(21)00874.
PMID: 34384775