Fetal head size and effect of manual perineal protection

Abstract

ObjectiveThe aim of this study was to evaluate whether a previously identified modification of Viennese method of perineal protection remains most effective for reduction of perineal tension in cases with substantially smaller or larger fetal heads.MethodsA previously designed finite element model was used to compare perineal tension of different modifications of the Viennese method of perineal protection to "hands-off" technique for three different sizes of the fetal head. Quantity and extent of tension throughout the perineal body during vaginal delivery at the time when the suboccipito-bregmatic circumference passes between the fourchette and the lower margin of the pubis was determined.ResultsThe order of effectiveness of different modifications of manual perineal protection was similar for all three sizes of fetal head. The reduction of perineal tension was most significant in delivery simulations with larger heads. The final position of fingers 2cm anteriorly from the fourchette (y = +2) consistently remains most effective in reducing the tension. The extent of finger movement along the anterior-posterior (y-axis) contributes to the effectiveness of manual perineal protection.ConclusionAppropriately performed Viennese manual perineal protection seems to reduce the perineal tension regardless of the fetal head size, and thus the method seems to be applicable to reduce risk of perineal trauma for all parturients.

Manual perineal protection: The know‐how and the know‐why

“…Indeed, computational analysis revealed that the degree of reduction in perineal strain at the fourchette is a determinant of where the thumb and index finger are placed on the perineum as well as the distance and direction of their medial movements. Based on measures of maximum perineal strain, minor alterations in these parameters were associated with a gradual reduction in the maneuver’s efficacy . Interestingly, all the respondents who provided correct and complete information about the MPP technique had <5 years’ work experience in maternity care.…”

“…Based on measures of maximum perineal strain, minor alterations in these parameters were associated with a gradual reduction in the maneuver's efficacy. 20,21 Interestingly, all the respondents who provided correct and complete information about the MPP technique had <5 years' work experience in maternity care. This information is particularly important for maternity units planning to adopt MPP because it highlights the importance of targeting all staff levels, irrespective of years of experience, when devising effective interventions for the implementation of MPP policy.…”

“…This is mainly achieved by a reduction in the transverse perineal tension using the accoucheur’s thumb and index finger alongside the vaginal opening . Subsequent computational biomechanical studies showed that such maneuver can produce up to a 30% reduction in relative tension in the perineal region, dependent on the precision of its execution . Indeed, the maneuver is most effective when the thumb and index finger were applied 12 cm apart, 2 cm anterior to the posterior fourchette and approximated medially by 1 cm on either side.…”

“…[17][18][19] Subsequent computational biomechanical studies showed that such maneuver can produce up to a 30% reduction in relative tension in the perineal region, dependent on the precision of its execution. 18,20,21 Indeed, the maneuver is most effective when the thumb and index finger were applied 12 cm apart, 2 cm anterior to the posterior fourchette and approximated medially study took place in three maternity units that support manual perineal protection policy in three European countries (Czech Republic, Slovenia and the UK). Our study demonstrated that the majority of participants are aware of the concept of manual perineal protection.…”

Metrics of Perineal Support (MOPS) Study

“…Our group has previously demonstrated that, during FMPP, the optimal placement of the thumb and index finger is two cm anterior of the fourchette and 12 cm apart. While the most effective distance and direction of movement is to approximate these digits by a distance of one cm on either side without changing their antero-posterior orientation to the fourchette [17,20,21,23]. Additionally, it has been also shown, that an imprecision of just one cm might increase the maximum strain at the perineum by up to 30% [20].…”