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Third Trimester

There is some diversity of medical opinion about exactly when the third trimester begins. The Office on Women’s Health at the US Department of Health and Human Services defines the third trimester as weeks 29–40, and PregnancyCorner follows their lead. However, the American Pregnancy Association and the UCSF Medical Center at the University of California, San Francisco both consider the third trimester to run from week 27 to week 40. Other experts say that the third trimester starts at week 28.

Third Trimester Pregnancy Symptoms

As your uterus grows larger, it will begin to crowd your other organs, resulting in symptoms ranging from urinary incontinence to shortness of breath. Your belly button may also pop out, even if you have an “innie.”

Other third-trimester pregnancy symptoms:

The increase in blood circulation may cause tiny red “spider veins” and blue or reddish varicose veins to appear beneath your skin, particularly on your legs.

Back pain and heartburn show up or tend to get worse. Leg cramps, especially at night, are common. Your pelvis and hips can develop sharp pains, and pubic bone pain is a common problem. Your feet may hurt, and walking even normal distances may become difficult. You do not sleep very well—you wake up frequently to urinate, and then you may have trouble getting back to sleep.

During the third trimester you may experience a nipple discharge known as colostrum. This is your body’s way of preparing for breastfeeding.

Potentially heavy vaginal discharge is common near the end of pregnancy, and some women experience Braxton-Hicks contractions and false labor.

If you notice any sudden or extreme swelling during the second trimester, or if you very suddenly gain a lot of weight, you should call your doctor immediately, as this may be a symptom of preeclampsia. Vaginal spotting is not unusual and is less of a concern than during the first trimester, but any bright red vaginal bleeding warrants a call to your obstetrical provider right away.

Some people say that pregnancy lasts as long as the patient can stand it … and then one more month! The last month is not easy—we call it “hitting the wall.” But this time is of vital importance for the final phase of fetal development, which includes optimal lung functioning and storage of extra baby weight in the form of baby fat and stored sugar in the liver (called glycogen). Your baby will gain a half pound a week for the last four to six weeks of pregnancy. Do your best to get plenty of rest this last month so your body can devote the majority of its energy and resources to that final push for fetal growth.

By the End of the Third Trimester

At 37 weeks your baby is considered full term, and after this point you may go into labor at any time. Eight percent of all births occur between 38 and 41 weeks of gestational age. By this time the baby should be about 19–21 inches long and weigh anywhere from six to ten pounds!

Read more about your week:

Medical References:

    The University of California, San Francisco—UCSF Medical Center http://www.ucsfhealth.org/conditions/pregnancy/trimesters.html Office on Women’s Health, U.S. Department of Health and Human Services http://womenshealth.gov/pregnancy/you-are-pregnant/stages-of-pregnancy.html The American Pregnancy Association http://americanpregnancy.org/while-pregnant/third-trimester/ The Mayo Clinic http://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/pregnancy/art-20046767
[Page updated July 2015]