That's weird with my first I was 140 and dropped to 130 at that many weeks and my doctor said its normal. If anything I've heard lots of doctors tell overweight women to lose weight. I wouldn't worry about it.
I lost a total of 13 lbs my first trimester and havent gained any of it back and im about to start my third trimester. Im 25.3 weeks. My dr isnt worried about me losing weight as long as im eating healthy and taking my vitamins. She said some women do not gain till later in their third trimester. I was 175 pre-pregnancy... idk if this helps you or not
It depends how much you lose I was 56kg & due to hypermesis & thyroid I went down to 49kg in a few weeks. It worked out to be over 10% of my body weight. They worry because I think more than 5% & malnutrition to you & your baby can become a very possible issue. All that said if you were over weight to begin with they recommend some woman to watch their weight whilst pregnant so it just depends on your circumstances I suppose