We conclude that the phase of delivery that causes a major increase in the area of the levator hiatus area and in the levator ani muscle area is when the fetal head reaches the 4th plane of Hodge. Furthermore, data in our paper indicates that the exact moment in which the avulsion of the levator ani muscle is produced is when the bulging of the fetal head on the maternal perineum occurs.

We have not observed differences in the LAM-avulsion rate between rotational forceps and non-rotational forceps performed by highly experienced personnel in instrumental deliveries.

The number of vacuum tractions needed to complete fetal extraction is not associated to a higher LAM avulsion rate nor with differences in levator hiatus area.

No abstract

Objectives: To study feasibility and reproducibility of a new image-scoring method for angle of progression (AOP) measurement by transperineal ultrasound (TPU). Methods: TPU was performed for 55 singleton pregnancies at term in second stage of labour. 55 images obtained by TPU were recorded and interpreted independently by three reviewers. A quality score on 8 points was defined for AOP measurement. Three criteria were ascertained as major, (2 points): line in the axis of the symphysis parallel with the pubic rami, fetal skull clearly visible, correct positions of callipers. Two criteria were ascertained as minor given (1 point): symphyseal capsule visible, zoom enough. No point was given when a criteria was not visualized. Using final scores, AOP measurements were classified into three groups of quality: good (6-8), intermediate (4-5), unacceptable (0-3). Agreement for distributions in quality groups were evaluated between pairs of reviewers. Triplets of values were used to assess the inter-observer agreement for AOP scoring in each quality group. ICC according quality groups were calculated to assess the effect of quality measurement on inter-observer agreement for AOP measurement. Results: Among all AOP measured, 12.7% were classified as unacceptable. Distributions in the three quality groups were not significantly different between the reviewers. There were no statistical difference for agreement between the three pairs of reviewers (Fisher test, p = 0.33). 19 triplets of values for good scores and 26 triplets of values for intermediate scores were used to calculate ICC. Inter-observer agreement for the AOP was sligthly better in the good quality group than in the intermediate group, ICC 0.79 (CI95%; 0.64-0.89) and ICC 0.59 (CI95%; 0.33-0.80), respectively. Conclusions: Using a reproductible image-scoring method for AOP, we demonstrated that non optimal measurement of AOP could affect its reliability. As 12.7% of AOP were classified as unacceptable, future studies should implement an image-scoring method to insure quality of AOP measurement.