When does each trimester begin

Our illustrated pregnancy calendar is a detailed guide to all the changes taking place in your baby — and in you. Each week of pregnancy includes a description of your baby's development, as well as an explanation of the changes taking place in your body. You'll also find important medical info that will help keep you and your baby healthy. After you announce your pregnancy, the first question you'll probably be asked is "When are you due? It's important to remember that your due date is only an estimate — most babies are born between 38 and 42 weeks from the first day of their mom's LMP and only a small percentage of women actually deliver on their due date.

During this period, your baby's body structure and organ systems develop. Most miscarriages and birth defects occur during this period. Your body also undergoes major changes during the first trimester. These changes often cause a variety of symptoms, including nausea, fatigue, breast tenderness and frequent urination.

Although these are common pregnancy symptoms, every woman has a different experience. For example, while some may experience an increased energy level during this period, others may feel very tired and emotional. The second trimester of pregnancy is often called the "golden period" because many of the unpleasant effects of early pregnancy disappear. Many of these symptoms arise from the increase in the size of your uterus, which expands from approximately 2 ounces before pregnancy to 2.

For many women, the first trimester of pregnancy is often the hardest. During this period, your body is going through a major transformation and needs time to adjust to the changes.

Pregnancy hormones, extreme fatigue, nausea and vomiting, tender breasts, and the frequent need to pee are common symptoms that make the first trimester the most challenging time for pregnant women. The third trimester is the final stage of pregnancy and can be considered to be the most painful.

During this stage, your baby is getting bigger, which puts more stress on your body that causes aches and discomfort. As your body begins to prepare for labor, a woman may have irregular contractions known as Braxton Hicks. The prenatal care you receive throughout your pregnancy is essential to the health of both you and your baby, and can improve the likelihood of a safe and healthy delivery.

Knowing what to expect the day of delivery helps, so make sure to take some prenatal classes to get you better prepared for your bundle of joy. The third trimester is considered to be the longest trimester of pregnancy. This trimester begins in week 28 of pregnancy and lasts until you give birth.

Most women begin labor around week 40 of pregnancy, while some pregnancies may take longer. If your pregnancy lasts more than 42 weeks, it is called post-term past due.