What is the primary change that happens to a human during the third trimester of gestation?

Q: Whats the third trimester of pregnancy?

Reaching week 27 of your pregnancy means youre now in the third and final trimester. While this trimester could end at week 40, in reality it ends whenever your baby is born. A baby is considered to have been born full-term if it is born in weeks 37 to 42 of pregnancy.

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Pregnancy the three trimesters
First Trimester (0 to 13 Weeks)
Second Trimester (14 to 26 Weeks)
Third Trimester (27 to 40 Weeks)
What happens in the third trimester of gestation?
What main change occurs during each of the 3 trimesters of fetal development?
What changes are happening to the mom during the third trimester of a pregnancy?
What's the third trimester of pregnancy?

Summary

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Your body changes during pregnancy. You may love some changes and feel uncomfortable with others.
You may experience of a lot of physical changes during pregnancy, or only a few.
You will probably have emotional ups and downs during pregnancy.
If you have depression or a mental illness during pregnancy, you need specialist care and treatment.
Some physical and emotional experiences are common to a particular trimester (stage) of pregnancy.

This page has been produced in consultation with and approved by:

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Content disclaimer

Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional. The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances. The State of Victoria and the Department of Health shall not bear any liability for reliance by any user on the materials contained on this website.

The Three Trimesters Obstetrics & Gynecology

Pregnancy the three trimesters

Pregnancy has three trimesters, each of which is marked by specific fetal developments. A pregnancy is considered full-term at 40 weeks; infants delivered before the end of week 37 are considered premature. Premature infants may have problems with their growth and development, as well as difficulties in breathing and digesting.

First Trimester (0 to 13 Weeks)

The first trimester is the most crucial to your baby's development. 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.

Second Trimester (14 to 26 Weeks)

The second trimester of pregnancy is often called the "golden period" because many of the unpleasant effects of early pregnancy disappear. During the second trimester, you're likely to experience decreased nausea, better sleep patterns and an increased energy level. However, you may experience a whole new set of symptoms, such as back pain, abdominal pain, leg cramps, constipation and heartburn.

Somewhere between 16 weeks and 20 weeks, you may feel your baby's first fluttering movements.

Third Trimester (27 to 40 Weeks)

You have now reached your final stretch of pregnancy and are probably very excited and anxious for the birth of your baby. Some of the physical symptoms you may experience during this period include shortness of breath, hemorrhoids, urinary incontinence, varicose veins and sleeping problems. Many of these symptoms arise from the increase in the size of your uterus, which expands from approximately 2 ounces before pregnancy to 2.5 pounds at the time of birth.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.

What happens in the third trimester of gestation?

During the third trimester, your fetus continues to grow in size and weight. The lungs are still maturing, and the fetus begins to position itself head down. By the end of the third trimester, the fetus is about 19 to 21 inches long and weighs, on average, 6 to 9 pounds.

What main change occurs during each of the 3 trimesters of fetal development?

In the first trimester, your baby will grow from a fertilized egg into a moving fetus with eyes, ears, and working organs. In the second trimester, your baby's features develop and you may be able to feel your baby move. In the third trimester, your baby will grow rapidly to get ready for birth.

What changes are happening to the mom during the third trimester of a pregnancy?

Your cervix (the lower end of your uterus) will begin to thin (effacement) and open (dilate). Braxton Hicks contractions (tightening of your uterine muscles) may happen more often and become stronger. This type of contractions can happen throughout the third trimester but get stronger as labor gets closer.

What's the third trimester of pregnancy?

Reaching week 27 of your pregnancy means you're now in the third and final trimester. While this trimester could end at week 40, in reality it ends whenever your baby is born. A baby is considered to have been born full-term if it is born in weeks 37 to 42 of pregnancy.