When you learn that you\'re pregnant, you might begin planning your pregnancy week by week. Every day you might have more questions about healthy pregnancy. What should you eat? Can you exercise? What type of prenatal tests should you consider? If you\'re carrying twins or other multiples, you might have even more questions about your pregnancy week by week. How much weight should you gain? How can you prevent preterm labor? Will you need bed rest? Whatever your questions, understanding your pregnancy week by week can help you make good decisions throughout your pregnancy. Learn nutrition do\'s and don\'ts, and get the basics on other healthy pregnancy issues — from exercise to back pain and marital life. The more you know about your pregnancy week by week, the more prepared you\'ll be to face what lies ahead. - First trimester The first few months of pregnancy — the first trimester — are marked by rapid changes for both you and your baby. For you, first trimester physical changes may include breast tenderness, fatigue and nausea. Your emotions may range from excitement to anxiety. For your baby, the first trimester is a time of rapid growth and development. Your baby\'s brain, spinal cord and other organs begin to form, and your baby\'s heart begins to beat. Your baby\'s fingers and toes even begin to take shape. If you\'re in your first trimester, make an appointment with your health care provider to begin prenatal care. You\'ll find out what to expect during the first trimester and beyond. What you learn can help you take the best care of yourself and your baby. - Second trimester During the second trimester of pregnancy — from months four to six — you may feel better than you did at first. Now\'s the time to enjoy your pregnancy! During the second trimester, your baby may begin to seem more real. Second trimester signs and symptoms may include larger breasts, a growing belly and skin changes. For your baby, the second trimester often marks the ability to kick, make facial expressions and hear. By week 20, you\'ll be halfway into your pregnancy. Regular visits to your health care provider remain important during the second trimester. Tell your health care provider what\'s on your mind, even if it seems silly or unimportant. - Third trimester The last few months of pregnancy — the third trimester — can be physically and emotionally challenging. Third trimester signs and symptoms may include backaches, swollen ankles and mounting anxiety. During the third trimester, your baby will likely open his or her eyes and pack on the pounds. This rapid growth may lead to more pronounced fetal movements. By the end of week 37, your baby is considered full term. During the third trimester, you\'ll continue to meet with your health care provider regularly. He or she may check the baby\'s position and assess cervical changes. As your due date approaches, continue to ask questions. Knowing what to expect during the third trimester can help you get ready for the final stages of pregnancy.