Milesy11~ a 1:235 chance for a child with DS is a VERY good chance your baby WONT have it!
also, it's really your girlfriends decision for the amnio... I think, PERSONALLY in your case, the chance for a M/C is greater than the chance for a baby with D/S
I speak from personal experience. I'm 22 yrs old and have a 10 month old son with down syndrome. I had an amnio at 16 weeks with him.
Here's the link to my journal, Please read it. it's got alot of facts about tests that can be done.
http://www.medhelp.org/user_journals/show/89768?personal_page_id=304