Computational modeling approach to study the effects of fetal head flexion during vaginal delivery.

OBJECTIVE The purpose of this study was to investigate the influence of fetal head flexion during vaginal delivery with a 3-dimensional computational finite element model. STUDY DESIGN A finite element model of the pelvic skeletal structure, pelvic floor, and fetus was developed. The movements of the fetus during birth were simulated in engagement, descent, flexion, internal rotation, and extension of the fetal head. The opposite forces against the fetal descendent and the stress of the pelvic floor muscles were obtained on simulations with different degrees of head flexion. RESULTS The simulated increase in fetal head flexion is associated with lower values of opposite forces against the fetal descent. The descending fetus with abnormal head flexion also meets resistance in later stations. Lower stress on the pelvic floor was demonstrated with simulated increase in fetal head flexion during vaginal delivery. CONCLUSION This analytic evidence suggests that the fetal head flexion during vaginal delivery may facilitate birth and protect the pelvic floor.

[1]  A. O'Boyle,et al.  Pelvic Organ Support Study (POSST): the distribution, clinical definition, and epidemiologic condition of pelvic organ support defects. , 2005, American journal of obstetrics and gynecology.

[2]  H. Dietz.  Pelvic floor trauma following vaginal delivery , 2006, Current opinion in obstetrics & gynecology.

[3]  T Mascarenhas,et al.  The influence of an occipito-posterior malposition on the biomechanical behavior of the pelvic floor. , 2009, European journal of obstetrics, gynecology, and reproductive biology.

[4]  M. Abitbol.  Adjustment of the fetal head and adult pelvis in modern humans , 1993 .

[5]  I. Grosse,et al.  Requirements for comparing the performance of finite element models of biological structures. , 2009, Journal of theoretical biology.

[6]  Daniel K. Moon,et al.  Biomechanical Adaptations of the Rat Vagina and Supportive Tissues in Pregnancy to Accommodate Delivery , 2007, Obstetrics and gynecology.

[7]  Jane M. Young,et al.  Incidence and Etiology of Pelvic Floor Dysfunction and Mode of Delivery: An Overview , 2009, Diseases of the colon and rectum.

[8]  R M Natal Jorge,et al.  The influence of the material properties on the biomechanical behavior of the pelvic floor muscles during vaginal delivery. , 2009, Journal of biomechanics.

[9]  T Mascarenhas,et al.  Finite Element Studies of the Deformation of the Pelvic Floor , 2007, Annals of the New York Academy of Sciences.

[10]  D. D'Esopo,et al.  A Roentgenologic Study of the Mechanism of Engagement of the Fetal Head , 1934 .

[11]  Tara Selman,et al.  Mechanism and management of normal labour , 2007 .

[12]  James A. Ashton-Miller,et al.  Levator Ani Muscle Stretch Induced by Simulated Vaginal Birth , 2004, Obstetrics and gynecology.

[13]  Frans C T van der Helm,et al.  Measuring morphological parameters of the pelvic floor for finite element modelling purposes. , 2003, Journal of biomechanics.

[14]  R. M. Natal Jorge,et al.  Deformation of the pelvic floor muscles during a vaginal delivery , 2007, International Urogynecology Journal.

[15]  R W Prager,et al.  Fetal head moulding: finite element analysis of a fetal skull subjected to uterine pressures during the first stage of labour. , 2001, Journal of biomechanics.

[16]  James A Ashton-Miller,et al.  On the biomechanics of vaginal birth and common sequelae. , 2009, Annual review of biomedical engineering.