You could write something like this:
“To prepare for the healthiest possible baby in my future, one of the things I would do is be sure to stay healthy. Staying healthy by regularly exercising and eating nutritious foods would make sure that I’d have a healthy baby too. I would also make sure to stay away from bad things like alcohol and drugs. One last thing I’d do to have a healthy baby is go to the doctor regularly so I can make sure I don’t have any diseases that could be passed down to the baby.”