When I went to for my first (and only) GP visit for preganancy my doc also was really pushy and weird about me having one. She said they can do them up to 20 weeks they just use a different thingy and don't rub as hard. I declined and said I wanted to discuss with my midwife, and I had never had any abnormal ones before - AND if they find something what the hell are they going to do?????? while you are pregnant?????
She was really strange though and then proceeded to tell me that patient who also had never had an abnormal whose results were in and they had a high range abnormality - so much for informed consent - I was pretty peeved at her attempt to scare me into it.

I did ask my midwife and she said no way - they will not do one while pregnant, and confirmed my thoughts about it being pretty pointless because what can they do if there is an abnormality? Wait until bub is born would be my guess....