How can I prevent amniotic sac disorders?

Need more info. If you are asking about too little amniotic fluid, avoid becoming a diabetic or hypertensive which can decrease fluid. If you are asking about too much fluid, avoid diabetes of pregnancy which can sometimes cause this. If you are asking about amniotic bands, etc then there really is nothing you can do to prevent them.
Need more info. There are so many possible issues related the amniotic sac, i would suggest you start with your ob/gyn doctor and discuss your specific concerns face-to-face.