When you find out you're pregnant, you might begin planning your pregnancy week by week. Every day you might have more questions about a healthy pregnancy. What should you eat? Can you exercise? What type of prenatal tests do you need?

If you're carrying twins or other multiples, you might have even more questions. How much weight should you gain? How can you prevent preterm labor? Will you need bed rest?

Whatever your questions, understanding pregnancy as the weeks and months go by can help you make good choices throughout your pregnancy. Learn nutrition do's and don'ts. Get the basics on other healthy pregnancy issues, such as exercise, back pain and sex. The more you know about what to expect, the more prepared you'll be to face what lies ahead.