What healthy habits should a pregnant woman develop?

No tobacco, alcohol. If you smoke or drink alcohol, you could be harming your baby. If you're not pregnant yet, it's best to stop smoking or drinking before you get pregnant. Talk to your doctor about getting support.
Consult you MD. Ideally starting pregnancy at a good weight , and continuing good balanced eating habits and exercise through out is a great habit. Taking prenatal vitamins regularly . Read about pregnancy and go to visit with a list of questions or concerns. If you have problems with pain, bleeding or decreased fetal movements, don't second guess yourself , call your md.