Hi Prabhakar,
First you need to find out what is the splitting criteria for the Deliveries in the copy control of Sales or Delivery documents.
http://scn.sap.com/thread/349783
Next you can find out if those items which has split has the same header data such that it can be consolidated in the invoice. If you want to look at the custom stuff then look at the copy control of the delivery to billing document setup for a particular Item.
http://scn.sap.com/thread/769119
Hope this is helpful.