Third trimester of pregnancy: know the symptoms and tests

We can conceptualize pregnancy as the process of fertilization between the egg and the sperm, in which the implantation of the embryo in the uterus occurs.

But for moms on call, a pregnancy can mean much more than that!

In addition to involving hormonal, financial and psychological changes, pregnancy brings an idea of ​​a fresh start. They are moments of emotion and joy for parents and family members.

The gestational period takes around 40 weeks, or 9 months. Find out more about the main changes in the third trimester of pregnancy!

What is the third trimester of pregnancy?

This period ranges from the 28th week to the 40th week and is represented by a considerable growth and development of the baby, which must be weighing around 2 kg. It is usually in the third trimester that childbirth takes place, being more frequent in the last 4 weeks.

Symptoms and changes in the pregnant woman

It is during the third trimester that anxiety with the arrival of the baby hits . That’s because, you will probably be organizing the baby shower, the suitcase of clothes to take to the hospital and finishing the preparations of the little room.

However, it is also during this period that major discomforts arise, such as excessive belly weight, difficulty sleeping, in addition to back pain and swelling, which we will explain better below:


This is one of the most characteristic symptoms of pregnancy. One of the common pains affects mainly the lower back, which runs from the middle to the end of the back.

In some cases, you may feel the need to use a wheelchair in order to make getting around easier and less painful.

Low back pain is a symptom that occurs due to all the strength used to support the uterus.

In addition to the back there may be pain in the legs, as well as discomfort in the vagina.

Sometimes, the pregnant woman may have the feeling that the pelvis bones are expanding, as if in a movement of the uterus to prepare the body to allow the baby to fit in the pelvis.

Read more: Stretch Marks in Pregnancy: types (red), best cream, how to avoid?

Difficulty sleeping

Some pregnant women have difficulty sleeping in the third trimester of pregnancy.

This is because a mixture of feelings can occur: anxiety about the arrival of the baby, stress , in addition to the increase in the belly and, consequently, weight. All of these symptoms, together, can cause breathing difficulties, as well as discomfort at bedtime.


Another very common and visible change in pregnancy during this period is swelling, both in the feet and in the thighs, ankles and fingers.

We can consider this swelling as a consequence of the enlargement of the uterus, which compresses the veins of the lower limbs and, consequently, creates a difficulty in blood circulation.

In addition, pregnant women may have greater fluid retention, which can be improved by drinking water and walking.

Another option is to let your legs straight up.

Heartburn and reflux

During pregnancy the muscles of the stomach and esophagus loosen. This makes it easier for gastric acid (responsible for digestion) to rise through the esophageal tube, causing the sensation known as “burning”.


It is common to feel more hungry at the end of pregnancy. This can have two explanations: anxiety and a faster drop in blood glucose, which can be considered a generalized predisposition in pregnant women, to a greater or lesser degree, depending on each woman.

Baby development in the third trimester of pregnancy

In the period of the third trimester, the baby should already be about 2 kilos and approximately 30 cm in length. It is during the last 3 months that the child dedicates his efforts, mostly, to increase his fat layer.

In addition, during the third trimester, the baby begins to peel off the eyelids, which allows him to start creating the ability to open and close his eyes.

Another curious point of this phase is that the baby begins to develop a sleep cycle, which can be perceived by the mother through the child’s movements.

It is also in the third trimester of gestation that there is the development of the ability to suck a finger or make the suction movement. This happens before the baby is born, just so that he is born knowing how to breastfeed.

From the third trimester, the mother can perceive the baby turning, in a movement to prepare for childbirth. To do this, he fits his head in the pelvis region.

What are the tests for the third trimester of pregnancy?

During the third trimester of pregnancy, it is necessary to repeat some tests performed previously to assess your health and that of the baby. Among them, we can mention:


This type of laboratory exam aims to collect data regarding possible changes and infections that you may have developed even before pregnancy.

In addition to the complete blood count , some blood tests aim to assess blood type, rh factor and other possible transmissible conditions, such as HIV , hepatitis B , rubella , toxoplasmosis and syphilis .

Read more: Genital herpes in pregnancy: what are the risks for the baby?

Cardiotocografia (CTG)

Also known as fetal monitoring, this test seeks to identify the baby’s heart rate, in addition to possible uterine contractions, in order to assess the baby’s well-being, especially in high-risk pregnancies.

Vaginal and rectal culture

The main purpose of this test is to determine whether there is a bacterium called Streptococcus Agalactiae. If its presence is confirmed, treatment with antibiotics should be carried out in order to protect the baby’s health at the time of delivery, since the child can be infected with this bacterium through contact with the vaginal canal.

Urine analysis

This exam aims to identify possible urinary infections, which, if flagged, should be treated even in the prenatal period.


Ultrasound in the third trimester aims to analyze the baby’s weight and growth, in addition to confirming the health of the umbilical cord and its structure. It also seeks to assess the conditions of the placenta, its location and positioning.

Tests for viral hepatitis B and C

If the presence of one of the two conditions is confirmed, it is necessary to vaccinate the newborn baby within 12 hours after delivery, in order to protect him from possible diseases and complications.

Menu for pregnant women in the third trimester

There is a common saying that a pregnant woman should eat for two. But you can ask yourself: what should I eat? Which food groups should I reinforce?

Well, there are several food options and healthy options to include in your daily routine.

But before that, it is worth reinforcing the importance of having a medical and nutritional monitoring, in order to prioritize food groups according to their needs.

In general, the feed should contain:

  • Oilseeds;
  • Food fibers;
  • Proteins;
  • Carbohydrates;
  • Vitamins and minerals;
  • A lot of water!!

Read more: Omega 3 and 6 in pregnancy may be related to ADHD

Tips and care for pregnant women

Some habits and initiatives can help you during this process of change.

These are simple tips, but they can help your health, that of the baby and even at the time of delivery. Check out:

  • Talk to the baby. This is a good initiative, which helps him to identify familiar voices, sounds and noises;
  • Look for a prenatal course for parents, which can facilitate understanding about the birth process and the changes that pregnancy brings;
  • Practice stretching and relaxation exercises that can facilitate labor. Some cool activities are: pilates, yoga for pregnant women and meditation. Before, remember to talk to your doctor.

Read more: Discover the benefits of pilates in pregnancy

The gestational process is unique. Therefore, it is recommended that you enjoy every moment, even when there is discomfort and discomfort, because soon, the baby will be born!

If you know someone who is pregnant, share these ideas and tips!