The Stages of Pregnancy: First, Second, Third Trimester

Your body goes through a number of changes during your pregnancy. Many use pregnancy trimesters to understand how far along they are before they are ready to welcome a new baby. First trimester, second trimester, and third-trimester pregnancy each come with unique physical signs as the child grows and your due date gets nearer.


This is an exciting and uncertain time for many soon-to-be parents. Knowing what you may expect and where to get medical support can make sure it is a healthy journey for you and your baby.

What Are Trimesters?

It takes about 37 to 42 weeks from conception to delivery. The countdown begins at the start of the mother’s last menstrual period before she conceives, which happens about two weeks later. The expected due date is about 40 weeks after the countdown starts. Pregnancy trimesters are the three stages in between. Each one lasts about three months.

How Do You Know If You’re Pregnant?

Taking a pregnancy test, at home or at your doctor’s office, is the only way to confirm your pregnancy. Some women suspect they are pregnant because of physical symptoms. Those include breast tenderness or swelling, nausea, fatigue, increased urination, moodiness, bloating, uterine cramping and light spotting. Often a missed period is a sign for many women they are pregnant.

First Trimester: What to Expect

The first trimester is about the first three months of pregnancy, or weeks 0 to 13. The first-trimester pregnancy symptoms are much like those early signs of pregnancy. You may experience nausea, breast tenderness, fatigue, and emotional changes. Some women get morning sickness at about week 6 of their pregnancy. You may notice weight gain, especially during the last few weeks of your first trimester.

Your baby’s organs and skeletal structure are beginning to develop. This is a good time to begin prenatal care by making an appointment to visit your family doctor or obstetrician.

Second Trimester: What to Expect

The second trimester lasts about three to four months, or weeks 13 to 28. During this time your body may have adjusted to the pregnancy. You may feel more comfortable, as nausea may dissipate and you may have better sleep. In the second trimester, your body has new pregnancy symptoms, as your baby is getting bigger. There may be back pain, abdominal pain, thigh pain, or swelling of the ankles and fingers. Your skin may change as well, as you may have stretch marks or “pregnancy mask,” which is dark patches of skin on the face.

You may feel your baby move, or feel the baby fluttering, during weeks 16 to 18. Your baby also begins to hear and swallow and has a regular sleep and wake cycle. By 20 weeks, you are halfway through your pregnancy. You should visit the doctor regularly to monitor your health and that of the baby.

Third Trimester: What to Expect

The third trimester is the last stage of pregnancy, lasting from about week 29 to 40. During this time your uterus will expand in size to about 2.5 pounds. That’s compared to about 2 ounces before the start of your pregnancy — and that doesn’t even count the weight of your baby! As your baby is getting bigger, there is pressure on your diaphragm and bladder. That leads to shortness of breath and frequent urination. You might also have hemorrhoids, varicose veins, and sleep challenges as your due date approaches. A pre-milk substance called colostrum may leak from your breasts.

Your baby will kick and move more. Most babies will turn head-down before the due date. During the third trimester, a baby typically gains 1/2 pound every week. Babies come in all sizes, but typically weigh between 6 and 9 pounds at birth. Your baby is full-term at 39 weeks. Regular visits with your doctor continue to be important during this time, as the delivery date comes closer.

When Should You See a Doctor?

It is important to make an appointment as soon as you know or think you might be pregnant. Working with a doctor is one of the best ways to support your health and that of your baby. Your doctor performs important tests during all stages of your pregnancy and offers advice on diet and lifestyle. As the time comes for the baby to arrive, your doctor can work with you to discuss delivery options.

Every pregnancy is unique. Your doctor is the ideal partner to develop the individualized health regimen that is best for you and your baby.

What to Expect at Your Due Date

No matter how many trimesters in a pregnancy, many new parents feel a mixture of anticipation and anxiety as the due date gets closer. You may have a delivery plan in place. You have likely already discussed birthing options with your doctor. Your medical history, experience of prior pregnancies, and personal choices all influence what will happen during the birth of your child. If you have already developed a strong relationship with your obstetrician, you have had an opportunity to evaluate these options and a “plan B” if there are unexpected factors when the baby is ready to arrive.

Why Choose Intermountain Health?

Intermountain Health, is dedicated to listening to your unique needs as an expectant parent. Over and above this dedication, Intermountain Health has an impressive roster of medical professionals to guide you through all stages of your pregnancy journey. That team includes OB/GYNs, nurse practitioners, and family doctors for high risk and normal prenatal care and delivery. Learn more by contacting us today to book an appointment.

Part of being well is being heard.