Hang on, to be clear, low blood sugars do NOT harm your baby. High blood sugars absolutely can harm your baby, but lows do not.
You're probably not on the US measuring system but my endocrinologist told me not to treat a low blood sugar unless it went under 60. I'm a diabetic all the time, not just when pregnant, and that's lower than what is normal for a diabetic. Lower blood sugars are natural in pregnancy. Women who aren't diabetic have naturally lowered blood sugars and they want gestational diabetics to emulate what happens to other women as closely as possible.
What kind of numbers are you talking about? How low is low?
If you do have a low blood sugar, here is how you treat it: take 15 carbohydrates worth of fast sugar, such as 4 oz of orange juice or sugary soda. Then eat something that is a carb plus protein, such as a peanut butter sandwich. If you're really low you might have to repeat the OJ. However, you don't want your sugar to go too high so you need to monitor before you take more of the OJ. You should see your sugar go up in about 15-20 minutes from the orange juice, and the sandwich is to help keep it up so it doesn't drop further.
Edit: Sorry it's hours later, I'm in the us and it's morning here for me now.
4.5 mmol/l = 81 mg/dl in my measurements, so by my endocrinologist's instructions you are not low enough to treat it. I emphathize totally - I hate the feeling of low sugars!
There's something else to consider. When you have had high blood sugars for a while, you "feel" a low blood sugar at a higher place than you would if your sugars had been normal. The fact that you're feeling low at about 80 means you probably had high sugars for a while. It's not dangerously low, it's completely within normal range. It just feels low because your sugars were previously too high.
60 mg/dl = 3.33333 mmol/l - that's the bottom of the range that my doctor gave me. Granted, that definitely feels low to me and I have treated a sugar at 64. But you do have some breathing room and you should expect to feel a little wonky until your system is used to running on lower sugars - lower but completely normal and healthy blood sugars.
The key if you're having lows is to keep testing. Test right before you eat and 1 hour after. If you're only testing 1 hour after you're not seeing your blood sugar at its lowest. It could be starting at about 80 and ending at about 80 (this happens sometimes) or it could be starting way lower and ending up there. So test both times. Good luck, and hopefully you can speak to your doctor soon.