<prompt> The time usually taken for air to reach the descending colon after birth in a normal infant is:l-2hrs3-4 hrs5-6 hrs8-9 hrs  <response>: Ans. d 8-9 hrs Since there is no gas in the abdomen of a new born baby, in case we are investigating a baby with ano- rectal malformations, the X-Ray to be done shall be an INVERTOGRAM and should be done after 8 hours as that would the time taken for air to reach the descending colon and performing the X ray shall be fruitful. 