I can understand you being concerned but I guess I'd ask myself whether there's a logical reason for the weight loss.

A friend of mine had lost 10kg by the end of her pregnancy but it was understandable. She was quite overweight beforehand and was a big drinker and eater. Obviously she cut out the drinking and all those calories disappeared from her diet and she ate more sensibly too.

I was similar - drank too much and ate too much before I got pregnant. By week 20 I hadn't gained a thing and by week 40 I'd gained 6kg. That was without being able to do any exercise either from week 28 because I could barely walk (unstable pelvis). Plus DD was 4kg so quite big.

But if your diet and exercise have remained the same as before pregnancy and there's no logical reason why you're losing weight, I'd mention it to your doctor.