I was diagnosed with what turned out to be T1, at the same time I found out that I was about 7 weeks pregnant... So for me straight on insulin...
The regimes were different back then 1989, so can't really advise concerning regimes as I'd be out dated but would suggest if you can, to maintain a strict regime, so xxx amount at carbs at xx time of the day, back then it was 3 main meals and 3 snacks a day....
I had large babies all normal births
oldest 10lb10z non-diabetic pregnancy
second 10lb12.5oz diabetic
third 11lb13oz
As you can see not the greatest difference between the non-diabetic and diabetic weights, the difference between my first two and last one can be explained, first two I smoked I did manage to cut back to a couple a day, but still smoked through the pregnancy, my youngest I had managed to quit smoking...
All 3 were normal births, did have forceps for my first, she was early at 38 weeks, and the other two I was induced at 37 weeks...
How they monitor diabetic mums now is a lot different than when I had mine, no combined clinics when I had mine, so major issues insuring my medical records followed me to each clinic (learnt to pre-warn out patients I be back tomorrow and not to send my records back)
but they monitor well, so when it comes to weight loss, they will be able to work out whether any is impacting on the baby or it's just your weight you're losing... I lost weight with all my pregnancies, if you lucky enough to lose your own weight during the pregnancy, be very careful after wards so easy to put it all back on....
A little bit of reassurance here, my 3 are adults now and non-diabetic. my youngest had my second grandchild back in the summer, she was high risk diabetes on two score, I'm T1 and she carries a lot of excess weight but she was fine, her pregnancies went well and my grandchildren are fine....