First of all, the effect of diet pills is questionable. The best way to lose weight is through diet control and proper activities. Some diet pills are ineffective. Second, even if some weight-loss drugs are effective, they may have an impact on the fetus during pregnancy and cannot lose weight during pregnancy. It is necessary to gain weight properly, which can promote the growth and development of the fetus and prepare for the final delivery and breastfeeding. Therefore, no matter from which angle you consider pregnancy, you can't take diet pills.