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third trimester of pregnancy

Alternative Names
late antenatal period

Pregnancy is the process of childbearing. Measured from the start of a woman's last normal menstrual period or LNMP, it usually lasts about 40 weeks or roughly 9 months.

The third trimester of pregnancy generally spans weeks 28 through 40, though healthy babies may be born a bit sooner or later. Although most women undergo many of the same physical changes during this time, no two pregnancies are alike.

What is the information for this topic?
During the third trimester, continuing growth and development in mother and foetus cause many changes to occur.

Women may notice:
  • movements of the foetus can be felt more strongly
  • abdominal pain that may or may not be true labour pains
  • shortness of breath because the uterus is pushing against the diaphragm. The diaphragm is a flat, strong muscle that aids in breathing. Towards the end of the third trimester, the baby may drop down into a lower position. This will make it easier for the mother to breathe.
  • a need to urinate more often when the baby drops down into a lower position in the pelvis
  • yellow, watery fluid leaking from her nipples, known as colustrum
  • her navel sticking out
As the body readies for birth, a woman's cervix begins to thin out and open.

During the third trimester, certain discomforts and mood changes may occur:
  • fatigue or extra energy, or alternate periods of both
  • increasingly heavy white vaginal discharge
  • more mild lower abdominal pains with uterine tightening and then relaxing
  • more or less of an appetite
  • constipation, heartburn and indigestion due to gastro-oesophageal reflux, gas, and bloating
  • headaches, dizziness, or faintness
  • more trouble sleeping
  • itchy abdomen
  • varicose veins
  • swelling of the legs, feet, and hands
  • increasing clumsiness as shape and balance changes
  • anxiety, impatience, and restlessness
  • irritability and unusual sensitivity
In the foetus:
  • as the foetus gets bigger, it has less room to kick and stretch, so the movements felt by the mother may decrease
  • fine body hair disappears
  • most bones harden, but bones of the head stay soft and flexible for birth
  • as the time for birth approaches, the foetus usually moves down into the pelvis and settles into a good position
At 40 weeks, the foetus is considered full term. It is about 20 inches long and weighs 6 to 9 pounds.

The most common health risks and concerns in the third trimester of pregnancy are:
  • premature labour beginning before the 37th week of pregnancy. If the labour cannot be stopped, the baby may be born too early. This can cause many problems with the baby's health and development.
  • vaginal bleeding
  • changes in foetal movements
  • rupture of the sac, or membranes, that surround the foetus
  • false labour
During the third trimester of pregnancy, monitoring is more frequent. In the seventh and eighth months, it may include:
  • mother's weight and blood pressure
  • urine test for sugar and protein
  • foetal heartbeat
  • height of the uterus
  • size and position of the foetus
Any worrisome symptoms or concerns should be reported to the doctor. After the 32nd week, the doctor may suggest monitoring every two weeks.

Monitoring occurs weekly after about the 36th week as the ninth month begins. It may include all of the above as well as examination of the cervix and discussion about the signs and symptoms of labour.

Author: Dr. Karen Wolfe, MBBS, MA
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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