12 lbs in 5 weeks is a lot to lose. ESPECIALLY if you aren't having morning sickness or are overweight. If you are eating the same then you might expect to lose a bit since your body is working harder and burning more calories. Since this weight loss has happened since your last OB appointment, you should call your OB and discuss this with him/her to make sure nothing else is wrong. If they say you are fine then all is good, but until they know what is going on, they can't offer you an opinion!
I amgree with the other 2 posters... I am almost 28 weeks and have not gained any weight so far.... Yes I am a little worried, but the doctors say it is normal for some people. As long as the baby is measuring fine and you are eating normally, there is nothing to worry about...
I agree with Shawndell...if your MD hasn't seemed concerned, I wouldn't be. Losing weight is actually pretty common, and not a big deal especially if you're a little bit overweight to begin with (don't know if you are). I lost 16 lbs in the first four months of my first pregnant...then I lost 12 in the first few months with my second. With this one - my third - I didn't lose any weight at first. But, I'm 27 weeks and haven't gained an ounce so far. I'm heavy to begin with, and don't really NEED to gain any weight. If you're eating well and feel good, I'm sure your baby is fine!
Tricia
Has your OB said anything about it? If not then, I wouldn't really worry about it with concern unless they mentioned it. I lost 12 1/2 pounds my first trimester as well, and my doctor didn't say anything about it, I did have severe m/s cause I wasn't able to eat, sleep, drink, or anything...So that was the cause for me. But if your worried about it bring it up to your doctor. Right now I'm 19 weeks and have gained 3 pounds. So everything will even out..