Simple Q&A D&D 3.5 (by RAW) XXI

[mattie_p]

A 744. No

Crawling
You can crawl 5 feet as a move action. Crawling incurs attacks of opportunity from any attackers who threaten you at any point of your crawl.

Additional clarification. Withdrawing is a full round action, in which a character can move double his speed. The SRD states "You may not withdraw using a form of movement for which you don’t have a listed speed. "

Unless the character has a listed crawl speed, or some other means of moving without getting up from prone (burrowing, perhaps) they cannot withdraw without getting up from prone.