<prompt> In instrumental vaginal delivery:Full cervical dilatation is the only pre-requisiteForceps are used in all cases of breech deliveryForceps may be used if ventouse failsVentouse can not be used in rotational occipito-transverseposterior delivery  <response>: In case of failed ventouse, forceps may be used. Ref: Textbook of Obstetrics By Dutta, 4th Edition, Pages 397, 398, 613-614 