[Rupture of membranes in case of internal podalic version: a risk for cesarean section on the second twin]. / Non-intégrité des membranes en cas de manœuvres : facteur de risque de césarienne sur deuxième jumeau.

OBJECTIVES: To evaluate if internal version with ruptured membranes is a risk factor of cesarean section for the second twin. PATIENTS AND METHODS: Two hundred and fifty-nine twins vaginal deliveries after 33 weeks of gestation from 1997 to 2009 in a level 3 maternity. A retrospective case-control study comparing two groups: cases of cesarean section on second twin and five twins vaginal deliveries following the case. Active management of the second twin delivery was performed with a short intertwin delivery. RESULTS: Eleven cesarean sections on the second twin were performed (4.2%). The main indication was failure of internal version. The risk of cesarean section was significantly greater when the internal version was performed with ruptured membranes (OR: 25.4 IC 95% [2.3-275.7] P<0.003) and when intertwin time delivery interval was increased (8.1±5.1 vs 16.7±6.3, P<0.001). DISCUSSION AND CONCLUSION: The rupture of amniotic membranes before or during the internal podalic version is associated with a risk of failure and cesarean for the second twin. We recommend to perform the internal podalic version with unruptured membranes according to the French recommendations.

Deformation and bursting of nonspherical polysiloxane microcapsules in a spinning-drop apparatus.

We analyze the deformation and bursting process of nonspherical organosiloxane capsules in centrifugal fields. Measurements were performed in a commercial spinning-drop tensiometer at different values of tube rotation. A theoretical analysis of the mechanics of initially ellipsoidal elastic shells subjected to centrifugal forces is developed where the deformation of the capsule is predicted as a function of the initial geometry and membrane elastic properties. For different types of organosiloxane membranes the Poisson number varies between 0 and 0.9. This phenomenon points to a considerable reduction of the membrane thickness at the onset of mechanical stress. Membrane-breaking processes always initiated at one of the pole ends of the capsules. Such rupture processes can be interpreted in terms of the derived theoretical model.