I'm in the same boat. Warren Kidson advised me to continue with metformin. I have a healthy 4 year old daughter and I was on metformin for the entirety of my preg with her.

The obs is concerned about me continuing with metformin as well and I'm 26 weeks preg. I would agree that her concerns seem to be based on metformin being an "unknown" drug as opposed to insulin.

I read a study that said 76% of women with PCOS would chose metformin as a treatment during preg again, and 27% of women who had PCOS and took insulin would go ahead with insulin in any subsequent pregnancies.

All the research I've done myself suggests that metformin has a positive effect on preg women with PCOS, reduced miscarriage rate, reduced rate of GB, and reduced rate of overweight (large) babies at birth.

The Diabetes Australia website states "Metformin safe in pregnancy but more research required". They are not going to say that if they have serious doubts about it's safety.

Feel free to email me and all the best with the end of your preg.