Friends this is one of those questions where we can derive the answer by excluding other options as very little information has been provided to us. Sudden post partum collapse – may be seen in all the four cases viz – amniotic fluid embolism, PPH, uterine inversion and eclampsia. But in case of PPH antecedent H/O excessive blood loss, in eclampsia – H/O antecedent convulsions and in amniotic fluid embolism – H/O abrupt onset of respiratory distress before collapse should be present, which is not given in the question so these options are being excluded. The clinical picture of acute inversion occurring in the third stage of labour is characterised by shock and haemorrhage, the shock being out of proportion to the bleeding. Since this a problem which occurs due to mismanaged third stage of labour, patient doesnot have any complain in the antenatal period or during labour. Uterine inversion – “It should be suspected whenever a woman has unexplained postpartum collapse.” Textbook of Obs, Sheila Balakrishnan, p 489