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The article presents a study on the method to assess fetal head descent in labor with transperineal ultrasound (TPU) imaging. It aims to examine TPU's feasibility and reproducibility, as well as its utility in distinguishing patients whose pregnancy results in spontaneous vaginal delivery from those requires operative vaginal delivery or Cesarean section for failure to progress. It also compares the evaluation of fetal station through digital examinations with concurrent TPU assessments.

Objective Three-dimensional (3D) ultrasound is gaining popularity in prenatal diagnosis. While there are no studies regarding the safety of 3D ultrasound, it is now widely performed in non-medical facilities, for non-diagnostic purposes. The present study was aimed at comparing the acoustic output, as expressed by thermal index (TI) and mechanical index (MI), of conventional two-dimensional (2D) and 3D/4D ultrasound during pregnancy. Methods A prospective, observational study was conducted, using three different commercially available machines (iU22, Philips Medical Systems; Prosound Alfa-10, Aloka; and Voluson 730 Expert, General Electric). Patients undergoing additional 3D/4D ultrasound examinations were recruited from those scheduled for fetal anatomy and follow-up exams. Fetuses with anomalies were excluded from the analysis. Data were collected regarding duration of the exam, and each MI and TI during 2D and 3D/4D ultrasound exams. Results A total of 40 ultrasound examinations were evaluated. Mean gestational age was 31.1 ± 5.8 weeks, and mean duration of the exam was 20.1 ± 9.9 min. Mean TIs during the 3D (0.27 ± 0.1) and 4D examinations (0.24 ± 0.1) were comparable with the TI during B-mode scanning (0.28 ± 0.1, P = 0.343). The MIs during the 3D volume acquisitions were significantly lower than those in the 2D B-mode ultrasound studies (0.89 ± 0.2 vs. 1.12 ± 0.1, P = 0.018). The 3D volume acquisitions added 2.0 ± 1.8 min of actual ultrasound scanning time (i.e. not including data processing and manipulation, or 3D displays, which are all post-processing steps). The 4D added 2.2 ± 1.2 min. Conclusions Acoustic exposure levels during 3D/4D ultrasound examination, as expressed by TI, are comparable with those of 2D B-mode ultrasound. However, it is very difficult to evaluate the additional scanning time needed to choose an adequate scanning plane and to acquire a diagnostic 3D volume. Copyright [ABSTRACT FROM AUTHOR]