I had this question while I was pregnant and never really got an answer so I thought I would document my experience here for anyone interested. A little background, I was diagnosed with gestational diabetes at 28-29 weeks pregnant with baby #3 (age 44yo). I began eating low carb after googling but still ended up on insulin at night for my stubborn fasting levels. Babybwas born just before 38 weeks with no complications. My blood glucose levels were on the lower side of the scale for diagnosis, fasting between 5.1 and 5.6mmol and post meals (2 hrs) usually high 5s into the 6s, but 7s and 8s after more carbs. I have continued low carb eating (still including a couple of slices of homemade sourdough rye or spelt bread and a piece or so of fruit per day) and the rest of what I eat is eggs, meat, dairy and vegetables, I usually avoiding the carby ones except for the odd meal where I have chickpeas or lentils in a curry (no rice). So far, I have no problem with my milk supply in relation to what I am eating. But I never had a supply problem with my previous 2 babies either. Where I have had a problem with supply this time though was because baby didn't open his mouth much so couldn't latch well. I also ended up with a lump in one breast which blocked the supply on one side for a number of days. I alleviated this with self-expression and eventually hired a breast pump andd pumped after feeds and 2 hourly. Now I have the opposite problem: a 3.5 week old baby and over 130ml per breast waiting to be drained when he could get by on 70- 80mls per feed. So I'm now in oversupply mode and must watch out once again for lumps that could become mastitis. Such a balancing act.. But I felt better seeing how much milk I was making so I could be confident he was getting enough despite my low carb eating.