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Third Trimester of Pregnancy

You are now in the last phase of your pregnancy. Hungry and exhausted as you are, just carry on a few more weeks as your baby will soon be ready to see the light of the world. He is rapidly gaining weight as he will be almost as big as a watermelon by the time you reach full term [1].

When does the third trimester begin

The third trimester starts with the beginning of week 27, ending with the delivery of your baby (around week 40) [2, 3].

Third trimester weeks

Month of Pregnancy Week by Week
Seventh month 27, 28, 29, 30
Eighth month 31, 32, 33, 34, 35
Ninth month 36, 37, 38, 39, 40

Baby development during the third trimester

Your baby weighs just over 2 pounds at the start of this trimester while the average weight of a baby at full term is around 7 pounds [4]. He will be considered full term once you hit the 38-week mark. Right now, his skin is gradually smoothening out with the developing fat layer while his finger- and toenails continue to grow. The bone structure is fully developed but has some hardening to do [2]. All the major organs are now in place; while most of them have already started working, the lungs continue to develop until the day of delivery [5].

By the 30th week, your baby can open and close his eyes [6], with his senses of hearing, smell and taste developing as well [7]. He is still practicing swallowing and inhaling the amniotic fluid, so his organs are ready to function on their own after birth.

Third Trimester

Third Trimester

Until now, there has been plenty of space for your baby to rotate and change position within the womb. But by the last few weeks of this trimester, he will get pretty congested [8], making it more likely for you to feel even the small fetal movements. Apart from the regular kicks and punches, you are probably feeling some fluttering movements too. That is your baby having occasional (and harmless) episodes of fetal hiccups [9]. Most babies get into a head-down position, dropping down the uterus gradually after the 34th-35th week, in preparation for birth [5].

Third trimester symptoms and body changes

Now that the second trimester is over, you are probably aching all over and feeling pretty tired, waiting for the arrival of the day of delivery. The most common symptoms women go through during the third trimester include Braxton Hicks contractions, round ligament pain, pelvic and back pain [10] as well as considerable pressure in the pelvic area as the baby moves down the birth canal.

Common symptoms like nausea, vomiting, dizziness, fatigue, frequent urination and depression [7, 11] may intensify during the last few months. It is also completely normal to feel out of breath, especially during the first few weeks of the trimester, due to the growing uterus putting pressure on your ribcage [10].

Weight gain during the third trimester

You need to gain about 1 pound per week in this trimester [12], so your total weight gain throughout the pregnancy is no more than 25-35 pounds [13]. Continue to follow a healthy diet as only 450 extra calories are required per day during these three months [14].

Third trimester tests and ultrasound

Most women have a prenatal check-up every two weeks during the third trimester. Some may even be asked to see their doctor at least once every week in the last month, depending on the medical history of the mother and the fetal development rate [15].

Third Trimester Ultrasound

Third Trimester Ultrasound

Routine procedures carried out at these visits include checking for anemia, group B strep infection, high blood pressure and any abnormalities in blood glucose levels [7]. The doctor may also perform an ultrasound in addition to checking the baby’s heart rate and measuring the fundal height to ensure proper fetal health [15]. Once you enter the last month, your doctor will perform a cervical exam during each prenatal visit to check for dilation and effacement (opening and thinning) of the cervix [16].

Things to keep in mind

Kick counts: Regular kick counts are essential to make sure everything is okay with your baby as he goes through the final stages of development. Your baby should move at least ten times within two hours during his active period [17]. Make sure to call your health care provider in case of reduced fetal movement [18].

Fetal nutrition: Follow a balanced diet full of vitamins and minerals as your baby has already started storing nutrients, like iron, calcium, and phosphorus, for his initial days in the world [2].

Traveling during the third trimester: Although flying is usually considered safe until the 36th week [19], it is recommended to take expert advice before making any travel plans this late in pregnancy.

Warning signs: Contact your doctor or midwife in case you experience abnormal symptoms like severe diarrhea, intense abdominal cramps, bleeding, extreme headache, changes in vision, sudden weight loss and increased vaginal discharge, as these may indicate serious complications like preeclampsia, gestational diabetes and premature labor [20].

Having said all of the above, try not to worry too much about any possible risks to you or your baby as most pregnancies end with the mother giving birth to a healthy baby. Just make sure to follow your physician’s guidelines, eat healthy and try to relax. Remember, stress and depression in the mother can also harm the baby.

Published on March 16th 2015 by .
Article was last reviewed on 17th March 2015.

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