Girls, does anyone know what diet is safe for a child? The endocrinolo…

Girls, does anyone know what diet is safe for a child? The endocrinologist said that I have gained too much weight (at 20 weeks) and weigh 11 kg. There was a screening at 20 weeks and I'm going to see a doctor at 22 weeks. I've been taking Euthyrox 50 mg, now I'm supposed to take two tablets. I don't know if anyone else takes such a dose?