PregnancyTrimestersThird Trimester of Pregnancy

Third Trimester of Pregnancy

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What to Expect in the Third Trimester

The home stretch! The 3rd trimester is comprised of weeks 27-40 (although some women deliver earlier than 40 weeks).

Symptoms in Your Third Trimester

While you’ve hopefully gotten over the morning sickness that comes with early pregnancy (see our articles on First Trimester and Second Trimester), the third trimester can bring a host of new symptoms due to your growing belly. These may include:

  • Discomfort related to a growing uterus
  • Insomnia
  • Swelling
  • Itching related to stretching skin
  • Sciatica
  • Braxton Hicks Contractions

Your Baby in the Third Trimester

During this trimester, your baby will go from being about 14.5 inches long and weighing two pounds at 27 weeks to being at least 19 inches long and weighing around six to nine pounds at 40 weeks.

He or she will go from being the size of a cabbage to the size of a pumpkin!

By around 32-36 weeks, your baby will settle into the position he or she is going to be in until birth (which is hopefully head-down, chin tucked, and facing your back, otherwise known as the cephalic presentation). If not, your baby is considered “breech,” or legs-down, and will require a Cesarean Section.

Your doctor will do a final ultrasound at around 36-37 weeks to confirm baby’s position and also estimate his or her weight.

Your Body in the 3rd Trimester

Your body will continue to change quite a bit in the 3rd trimester. The more your belly grows, the more it can cause aches and pains such as sciatica, round ligament pain, and frequent urination.

If you haven’t already you may begin to experience Braxton Hicks Contractions, which are sometimes called “practice” contractions. They are totally normal; think of them as your uterus’ way of practicing for the real deal. They may feel like your abdomen tightening and can happen randomly or after exercise.

Feeling itchy?

The stretching skin on your belly may cause itchiness. This feeling is normal and should resolve with some lotion or oil. If the itching is intense and occurring all over your body, be sure to mention it to your doctor so they can rule out other causes.

What is Preeclampsia?

You may notice your doctor is paying special attention to your blood pressure, especially in the 3rd trimester. They are monitoring for preeclampsia, which is a condition defined by hypertension (high blood pressure) in pregnancy. Besides watching out for elevated blood pressure, they may also test your urine for the presence of protein, which indicates damage to the kidneys that can be caused by preeclampsia. If your doctor is concerned, they will order some lab work to investigate further.

Other symptoms to watch out for: swelling, headaches, nausea, shortness of breath, or changes in vision.

Doctor’s Visits

You will see your doctor increasingly often during the 3rd trimester.

First, you’ll see your doctor around 28 weeks for a routine visit, during which you’ll have a screening for gestational diabetes. To do so, you’ll drink a 50-gram glucose drink and have your blood drawn one hour later. If your glucose comes back high, you’ll be asked to return for the 3-Hour-Glucose Tolerance Test to confirm whether you have gestational diabetes.

You’ll be seen for another routine visit at 32 weeks. Nothing special about this visit – just a normal check-up!

You’ll then come back at around 36 weeks for another routine appointment. Around this time, your doctor will swab you for Group B Strep, which is bacteria that are commonly present in our bodies. While it does not pose a risk to you, it can be dangerous for your newborn baby who could contract it from you during vaginal birth. If you test positive for GBS, worry not — your provider will simply treat you with intravenous antibiotics during labor.

After 36 weeks, your provider will likely want to see you weekly until delivery. Depending on certain factors, they also may want to do a cervix check during these last visits to see if your cervix is becoming dilated or effaced (potential signs that labor is near).

Sometime around 37 weeks, you will have your final ultrasound, during which measurements will be taken to estimate fetal weight as well as the amount of amniotic fluid present.

Toward the end of your pregnancy, your provider may also recommend a Nonstress Test or “NST,” which is a non-invasive test that involves attaching two monitors to your belly for 20–30 minutes. These monitors track contractions, fetal movement, and fetal heart rate.

What about a Birth Plan?

During the 3rd trimester, it’s important to communicate with your doctor or midwife about expectations and preferences during your birth experience.

Some things to consider when creating your birth plan:

  • Pain control. Are you planning to get an epidural? If not, what methods will you use to manage pain during labor?
  • Environment. Would you like the lights to be dimmed, when possible? What about noise level? Think about the type of environment you’d like to create to make yourself as comfortable as possible.
  • Partner involvement. What will your partner’s role be during labor? Consider the types of emotional and physical support you’d like them to provide. If you’d like them to cut the umbilical cord or attempt to “catch” the baby, you should communicate this to your provider beforehand.

Having a Cesarean Section? You can make a birth plan for this as well, such as requesting that your partner be present at all times and that your arms are not restrained, if possible.

Feeling Nervous?

Know that it’s normal to feel fear or apprehension in the final weeks leading up to birth. Take a deep breath and think of all the amazing women in your life who have gone through this experience before.

For some, scheduling a hospital tour prior to labor is helpful for taking away some of the unknown of what the birth experience will be like.

Before you know it, your baby will be in your arms!


When does the third trimester start?

The third trimester runs from week 27 to 40.

How many weeks long is the second trimester?

This 3rd trimester lasts for 13 weeks (although some women deliver earlier than 40 weeks).

What is a Nonstress Test or NST?

A Nonstress Test (NST) is a non-invasive test that involves attaching two monitors to your belly for 20–30 minutes; the monitors track contractions, fetal movement, and fetal heart rate.

In this series

First Trimester: Read our guide to the first trimester of your pregnancy.

Second Trimester: Read our guide to the second trimester of your pregnancy.

Third Trimester: This guide.

Routine blood tests during pregnancy: Our guide to the blood tests you’ll be recommended during pregnancy

Written by

Abigail Purcell, RN
Abigail Purcell, RN
Abigail is one of our expert writers and is a BSN, RN (Registered Nurse) with a wide range of experience. She has worked in Public Health, Medical-Surgical nursing, and, most recently, Paediatrics and Women’s Health. Her true passion is serving mothers and families by helping them navigate their healthcare. As a nurse writer, Abby enjoys being able to empower patients on a larger scale, using evidence-based information that is easy to access and understand.


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