Comparing forces on the fetal neck in breech delivery in lithotomy versus all-fours position: a simulation model

Abstract

Purpose: To measure forces applied to the fetal neck, in a simulation model for breech delivery, in both lithotomy versus all-fours position.

Methods: We used a Laerdal SimMom simulator and a Birthing Baby together with PROMPT Flex Software. The descent of the fetus was accomplished using the Automatic Delivery Module 2. The baby was always in breech position; the SimMom in either all-fours or lithotomy positions. Sensors were located inside the fetal neck region to simulate forces applied to the plexus.

Results: The lowest force on the fetal neck region was recorded for the delivery in all-fours position without further maneuvers (mean force 58.70 Newton, standard deviation 2.54 N). As weight was added to the baby, the force increased (i.e. + 500 g, mean force 71.8 N, SD 3.08 N, p < 0.001). Delivery in lithotomy position resulted in a mean force of 81.56 N (SD 19.55 N). The force significantly increased in case of delivery of the head without assistance from contractions (mean force 127.93 N, SD 23.10 N). In all-fours position, the delivery of the fetal head from pelvic floor level without contractions (Frank's Nudge maneuver) resulted in a mean force of 118.45 N (SD 15.48 N, p = 0.02). Maneuvers for shoulder dystocia (the inverted type that can occur during breech delivery) led to significantly higher mean forces independent from birthing positions.

Conclusion: Breech delivery in all-fours position was associated with the lowest force acting on the fetal neck in our simulation model.

Keywords: All-fours position; Brachial plexus; Breech delivery; Lithotomy position; Simulator; Spontaneous vaginal breech delivery.

Fig. 1

Experimental setup with the full body obstetrical simulator in all-fours (A) and in lithotomy position (B)

Fig. 2

Forces measured in the fetal neck over time in uncomplicated deliveries. A Exemplary run-in all-fours position without application of external force and increased fetal bodyweight by application of a 500 g additional weight around the fetal belly. a¹ Navel visible; b¹ scapule visible; c¹ spontaneous birth of arms; d¹ spontaneous birth fetal head; [N] Newton. B Exemplary curve of a setup in lithotomy position while using the Bracht maneuver, which is the routine procedure in Germany. a² Scapule visible; b² spontaneous birth, fetal head; [N] Newton

Fig. 3

Forces measured in the fetal neck over time and in comparison, in uncomplicated and complicated deliveries. A Exemplary run: comparison of the forces affecting the fetal neck region with either the Frank’s Nudge [all-fours] or Bracht maneuvers [lithotomy position] from pelvic floor level without contractions. B Plots of maximum force levels in uncomplicated deliveries in all-fours position and in lithotomy position using the Bracht maneuver and complicated deliveries without contractions using Frank Nudge [all-fours] or Bracht [lithotomy position] maneuver from pelvic floor level. The performance of each maneuver was operator depended [Kruskal–Wallis test p < 0.01]. AF all-fours, SP lithotomy position, [N] Newton

Fig. 4

Forces measured in the fetal neck over time for shoulder dystocia in all-fours position. And lithotomy position. A, B Exemplary curves of runs with shoulder dystocia in all-fours position (A) and Bickenbach maneuver with Veit–Smellie–Mauriceau maneuver in lithotomy position (B). a¹ First shoulder; b¹ second shoulder; a² first shoulder; b² second shoulder; c² Veit–Smellie–Mauriceau. C Individual values regarding the maximal applied force in complicated deliveries with shoulder dystocia. A large scattering is shown using the different maneuvers within a scenario of shoulder dystocia in all-fours positions and using the Bickenbach and Veit–Smellie–Mauriceau maneuver in lithotomy position. The performance of each maneuver was operator dependent [Kruskal–Wallis test p < 0.01]. [N] Newton