<prompt> All the following can be a cause for obstruction of after coming head of breech Except:HydrocephalusPlacenta previaIncomplete dilatationExtended head.  <response>: Ans. b. Placenta previa. Ref. Dutta Obstetrics 5th ed. 402BREECH PRESENTATION Most common type is complete breech in multipara and frank breech 70 in primi. Prematurity is the commonest cause. Other causes are uterine malformations recurrent breech and hydrocephalus. Denominator--sacrum Commonest positions--left sacroanterior Perinatal mortality rate is 3-10 in uncomplicated breech. Foetal mortality is least in frank breech and maximum in footling presentation. Gynaecoid and anthropoid pelvis are favourable for after coming head of breech. After coming head of breech is an indication for external cephalic versionThere is no consensus that after coming head of breech can be obstructed by placenta previa.PLACENTA PREVIA Placenta implanted wholly or partially in the lower uterine segment. 28 of women scanned before 24 weeks gestation have a low lying placenta - 3 at term. Trans-vaginal scanning improves accuracy of diagnosis of placenta previa especially with posterior placenta.- If the placenta encroaches or covers the internal cervical os then there is MAJOR placenta previa otherwise there is MINOR placenta previa. This has replaced grades I - IV. Risk factors- Increasing maternal age smoking previous caesarean section previous placenta previa - 4-8 recurrence risk Maternal risks- Haemorrhage related mortality- PPH- Complications of caesarean section post-partum sepsis- Placenta accreta up to 15 of placenta previaRecurrence risk Fetal risks- Prematurity- IUGR- Congenital malformations double risk of serious malformation- Mal-presentation. 