RESUMO
OBJECTIVES: To evaluate the association between ultrasound measured angle of progression (AoP) during labor and time to delivery (TTD) or second stage of labor duration (SSLD). METHODS: This systematic review (SR) was reported according to PRISMA statement 2020. Databases investigated were MEDLINE, CINHAL, Embase, Scopus, Web of Science. Other sources were references or related articles of included studies, Google Scholar, clinicaltrials.gov, thesis, expert groups. Main keywords: angle of progression, transperineal ultrasound, delivery, labor. Inclusion criteria were observational studies, single term pregnancy, cephalic presentation, AoP measurement during the first stage of labor or at the beginning of the second stage, without date restrictions. Language included: English, Italian, French, Spanish. Studies selection, evaluation of the risk of bias with Quality in Prognosis Studies (QUIPS) tool, and data extraction were carried out by two authors blindly and independently, with disagreement resolution by a third author. Qualitative summary of the results. This SR was registered on PROSPERO, number CDR42021232015. RESULTS: Of 428 records, 14 were included, published from 2009 to 2021, cumulatively analyzing 2498 women. All studies highlighted an inverse relationship between AoP and TTD. Some have identified an AoP cutoff, contained in a range between 110° and 129°, beyond which the duration of labor is significantly shorter. Others, a range between 137° and 160°, beyond which the duration of the expulsive period is significantly shorter. Finally, some factors influence this association: parity, epidural, and oxytocin. CONCLUSIONS: This SR confirms a significant association between AoP in labor and TTD. In clinical practice, AoP could help to predict the duration of labor, facilitating decision-making. The main limitations of this SR were the low number of included studies, their heterogeneity, and the high risk of bias related to confounding factors. For future research, further studies are needed to increase the strength of the evidence, obtain stratified results according to patients' characteristics and investigate groups of patients who have not yet been evaluated.
