With my last pregnancy I lost 3 kilos in a week and miscarried the following week. I did not realise it at the time but sudden weight loss in early pregnancy is a sign of an impending miscarriage That said it can also just be because of m/s or it could be because you are eating far healthier than before.... but I think you generally lose it gradually if this is the case. I'd only be concerned if the weight loss was rapid like mine was.