The influence of pelvic muscle activation during vaginal delivery.

OBJECTIVE

To estimate the influence of pelvic floor muscle activation during vaginal delivery using a three-dimensional computational finite element model.

METHODS

A computational finite element model of the pelvic skeletal structure, pelvic floor, and fetus was developed. The movements of the fetus during birth, in vertex position, were simulated; namely, the engagement, descent, flexion, internal rotation, and extension of the fetal head. The opposite forces against the fetal descent and the stress on the pelvic floor muscles were obtained in passive, 5%, 10%, and 15% pelvic floor muscle simulated activations.

RESULTS

The increase in pelvic floor muscle activation was associated with higher values of forces against the fetal descent. The descending fetus encountered increasing resistance in higher stations with the increase in pelvic floor muscle activation. The maximum values of stress of the pelvic floor muscles were obtained in +4 station. The increase in pelvic floor muscle activation was also followed by higher values of pelvic floor stress.

CONCLUSION

This study demonstrates the feasibility of using a computational modeling approach to study parturition. This experimental evidence suggests that the pelvic floor muscle activation during vaginal delivery may represent an obstacle to fetal descent and increase the risk for pelvic floor injuries.

LEVEL OF EVIDENCE: III.