ABSTRACT
INTRODUCTION AND HYPOTHESIS: A mathematical model to estimate membrane tensions (Mt) at the urogenital hiatus and midpelvis in patients with and without prolapse is proposed. For that purpose the complex structures of the pelvic floor were simplified and, based on assumptions concerning geometry and loading conditions, Laplace's law was used to calculate Mt. The pelvic cavity is represented by an ellipsoid in which the midpelvic and hiatal sections are described by an ellipse. The downwards forces within the pelvis (F(in)) are in equilibrium with the support forces within its walls (F(w)). F(in) is the abdominal pressure (PABD) multiplied by the area A of the ellipse. The force inside the tissues (F(w)) is distributed along the circumference of the ellipse C. The Mt can be approximated as Mt = (PABD.A)/C (N/m). Mt-α accounts for the angle α which describes tissue orientation with respect to the anatomical section and is calculated as Mt-α = Mt/sin(α). METHODS: We conducted a retrospective study on archived magnetic resonance imaging scans (n = 20) and ultrasound images in patients with (n = 50) or without prolapse (n = 50) and measured actual geometrical variables. PABD was measured in patients with and without prolapse (n = 20). RESULTS: Mt at the urogenital hiatus at rest is 0.35 N/cm. They significantly increase with the Valsalva manoeuvre, by a factor of 2.3 (without prolapse) to 3.6 (with prolapse). CONCLUSIONS: Calculated Mt are much lower than what is reported for the abdominal cavity. Prolapse patients have significantly larger Mt, which during the Valsalva manoeuvre increase more than in healthy subjects.
Subject(s)
Models, Biological , Pelvic Floor/physiology , Pelvic Organ Prolapse/physiopathology , Adult , Aged , Aged, 80 and over , Case-Control Studies , Female , Humans , Magnetic Resonance Imaging , Middle Aged , Mucous Membrane/physiology , Pelvic Organ Prolapse/diagnostic imaging , Pressure , Stress, Mechanical , UltrasonographyABSTRACT
OBJECTIVE: To determine a possible relationship between neonatal and maternal outcomes in twin gestations and the planned mode of delivery. STUDY DESIGN: A single-centre retrospective cohort study in twins > or =32 weeks of gestational age was performed. Baseline characteristics, and neonatal and maternal outcomes were documented according to the planned mode of delivery: a planned caesarean section or a planned vaginal birth. Statistical analysis was performed using chi-square test. Fisher exact test was used in case correction was needed. RESULTS: During the study period (1999-2002), 164 twins > or =32 weeks were enrolled in the study. In 29 women (17.7%) an elective caesarean section was performed. The remaining 135 twins (82.3%) were allowed to start a vaginal delivery. An emergency or an urgent secondary caesarean section for both twins was performed in 26 women, and in 2 women for twin B only. One twin B baby died during planned vaginal delivery. No significant differences in perinatal mortality and serious neonatal morbidity were found between both groups (10.3% versus 9.6%). Neonatal outcomes in twins A were significantly better than in twins B (2.4% versus 7.3%), independent of the planned mode of delivery. Serious maternal morbidity was not significantly different between both groups (13.8% versus 19.3%), although 2 women in the elective caesarean section group needed a relaparotomy for haemorrhage. CONCLUSION: Our results do not support an elective caesarean section for twin gestations > or =32 weeks. The success rate of vaginal delivery in the planned vaginal birth group was nearly 80%.
