I think 100 carbs a day while pregnant is great, if you can do it. I was pregnant last year and also have hypothyroidism, so I have a few comments as the pregnancy resulted in a huge weight gain for me.

Are you on any medication for your thyroid? Synthroid is safe while pregnant. If you're not, talk to your OB about it. Thyroid problems can cause some issues in pregnancy.

Also... this is just a general comment rather than a suggestion. You are going to be starving. I was hungry ALL of the time while pregnant. For awhile, I thought it was all in my head... but I really was that hungry. You are going to crave things. The cravings will be strong. If you crave something, just eat it.. in moderation just enough to get rid of the craving, but otherwise it could stress you out and you don't need that while you're pregnant. I breastfed after giving birth and I found with my thyroid issues that I absolutely could not lose weight while breastfeeding and I continued to be hungry all of the time. I decided to suck it up and deal with my weight while breastfeeding because I felt it was best for the baby, but I got to a point where I REALLY needed to lose the weight. My knees were killing me and I was exhausted all the time, and not from the baby. The baby is actually very easy going, so he's never kept me up too much at night. After 7.5 months of breastfeeding, I decided to quit so I could lose the weight. I realized I needed to be able to function properly to take care of the baby.

Anyhow, make SURE your weight is monitored carefully during your pregnancy. This isn't just one of those things people say... I really mean it. With hypothyroidism, you're already going to be more prone to gaining weight. You're going to be hungry all the time soon. If you're hungry, you need to eat. Don't let your weight get in the way of taking care of yourself.

What you need to do is express your concerns to your OB, have your weight monitored regularly, and figure out a diet that your OB thinks is safe. If your OB has an issue with any kind of low-carb while pregnant, switch doctors. A lot of doctors will put pregnant women that are gaining too quickly on a version of low-carb that is specifically for pregnant women.

Anyhow, I really mean all this because I kind of took the wrong path as I had no advice, support, or insight about the weight stuff during my pregnancy and I gained back all the 85lbs I'd lost back in 2004/2005 and then some. I would hate to see anyone suffer the same fate as me.