When does the third trimester start is the final step toward motherhood, beginning officially at the 28th week of pregnancy. The last three months of pregnancy or this stage is very important for the full development of the baby, so special precautions and care are required during this time.
According to research and medical science, the third trimester or the last three months of pregnancy begins at the beginning of the 28th week. This period extends until the ninth month or before delivery. If you know when does third trimester start, you can easily accept the sudden changes in your body. At this stage, due to the large size of the uterus, you may experience pain in the lower back and it is normal to feel some difficulty in breathing. Also, problems like tension in the leg muscles or swelling of the ankles may occur. When does third trimester start, you should understand this and increase the level of calcium and iron in your daily diet, because the baby’s bone structure is the strongest during this period. Regularly checking blood pressure and keeping sugar levels under control are one of the main tasks of this stage.

When does the third trimester start?
According to medical rules, the third trimester is counted from the 28th week of pregnancy. This stage usually lasts for 40 weeks or until the birth of the child. Knowing When Does Third Trimester Start is of immense importance because from this time the brain and lungs of the fetus begin to mature rapidly. During this stage additional pressure is created on the mother’s body, which can cause problems like back pain or shortness of breath. It is necessary to understand When Does Third Trimester Start and make changes in your lifestyle. During this time, water may enter the body and sleep may be disturbed due to hormonal changes.
Week and month calculation
- This last stage basically starts from the beginning of the seventh month of pregnancy and it exists until delivery, which is exciting for every mother.
- Signs of physical changes
- Swelling of the hands and feet at this time and feeling the pressure to urinate frequently indicate that your body is now preparing for the final preparation for delivery.
- Mental preparation time
- As the third trimester begins, mood swings can occur due to hormonal changes, so it is important to have family support and maintain your own mental peace during this time.
Special features of the last stage of pregnancy
When you know that When Does Third Trimester Start, emphasize counting the baby’s kicks or movements. During this time, the baby is more active than before and starts responding to external sounds. When Does Third Trimester Start You should be careful in your daily activities by understanding this. Avoid standing for long periods or lifting anything heavy during this time. Include enough iron and calcium in your diet so that the body maintains strength during delivery. Go for regular checkups as per the doctor’s advice and maintain the right balance of your weight. When Does Third Trimester Start From that time onwards, it would be wise to pack your delivery bag and keep emergency contact numbers handy.
How Pregnancy Trimesters Are Divided
The entire period of pregnancy is usually considered to be 40 weeks. This period is divided into three equal parts, called ‘Trimesters’. Each trimester indicates a specific stage of the baby’s growth and different changes in the mother’s body.
Below is the division of time according to the trimester:
1. First Trimester
- Duration: From week 1 to the end of week 13 (1st – 3rd month).
- Importance: This is the most important period of pregnancy because during this period the main organs of the fetus (heart, brain, hands and feet) are formed.
2. Second Trimester
- Duration: From week 14 to the end of week 26 (4th – 6th month).
- Importance: This is called the ‘golden period’ of pregnancy. During this period, the initial nausea or fatigue decreases and the baby starts to grow rapidly. The mother feels the baby move for the first time.
3. Third Trimester
- Duration: 27 weeks to 40 weeks or until delivery (7th – 10th month).
- Importance: This is the final preparation period. The baby’s weight increases rapidly and the lungs mature. The mother begins to feel physical stress and signs of labor during this period.
Some important information about calculating the trimester
- Calculating from LMP: Pregnancy is calculated from the first day of your last period, although conception occurs about 2 weeks later.
- Months vs. Weeks: Although pregnancy is considered to be 9 months in months, doctors use 40 weeks or 280 days for the correct calculation.
- Check-ups: At least one or more ultrasounds or check-ups are required in each trimester to understand the condition of the baby.
Why is the 28th week considered the beginning
There is a special medical rationale behind considering the 28th week of pregnancy as the beginning of the third trimester. Although the beginning of 27 weeks is often considered the beginning of this stage completing 28 weeks is considered a very important milestone.
The main reasons for this calculation are:
Viability of the baby: According to medical science the possibility of a baby surviving outside the womb or viability increases significantly after completing 28 weeks. It is very difficult and risky to save a baby if it is born before this time, but it is much easier to save babies born after 28 weeks with modern medical treatment.
Completion of seven months: Completing 28 weeks of pregnancy means that you are completing the 7th month of your pregnancy. This is the very beginning of the last three months of pregnancy (7th, 8th and 9th months).
Rapid weight gain and organ formation: From 28 weeks, the baby begins to accumulate fat very quickly and its lungs acquire the initial ability to breathe outside air. From this time on, the baby’s growth pattern is completely different and dynamic than in the previous two trimesters.
You may also read: last three months of pregnancy
Difference between 27 and 28 weeks
Many doctors consider the beginning of the 27th week to be the third trimester because it is one third of the total 40 weeks (one trimester of 13.3 weeks)
Baby’s condition at 28 weeks
- Eyes open: The baby can open its eyes for the first time at this time and responds to light.
- Brain development: Brain tissues begin to become complex rapidly and the baby begins to dream.
- Hiccups: The mother often experiences rhythmic hiccups during this time due to the baby’s breathing exercises.
What changes occur in the body when the Third Trimester begins
During the third trimester or the last three months of pregnancy, your body goes through major changes in preparation for the rapid growth of the baby and delivery. During this time, the size of the uterus increases significantly, affecting almost every organ in the body.
Major physical changes:
- Expansion of the uterus and size of the abdomen: Your uterus now extends well above the navel. As a result, the skin on the abdomen becomes taut and in many cases, stretch marks and itching appear.
- Shortness of breath and wheezing: As the uterus pushes upward, it puts pressure on the diaphragm below the lungs. This can make it difficult to take a deep breath and you may feel wheezy with little effort.
- Digestive problems and heartburn: Due to the influence of hormones, the stomach valve remains relaxed and the pressure of the uterus pushes stomach acid up into the throat. This can delay digestion and cause severe acidity or heartburn.
- Pelvic and lower back pain: As the baby gains weight, your body’s center of balance shifts. Hormones also soften the joints, which can cause pain in the lower back or groin while walking.
- Breast changes: Your breasts may enlarge and your nipples may start to secrete colostrum (a light yellowish fluid) as part of your preparation for labor.
Changes in baby’s movements

During this stage, your baby may not be able to move around as much as before because the space inside your uterus has decreased; instead, you will feel your baby’s strong kicks, elbow bumps, or body twisting movements much more clearly.
Other common symptoms
Swollen legs and varicose veins: Slow blood circulation and excess weight can cause your feet and ankles to swell.
Frequent urination: The baby’s head is downward or pressing on the bladder, causing the need to go to the toilet frequently.
False pain or Braxton Hicks: Sometimes you may feel mild cramping or period-like cramps, which subside with rest.
How does the baby grow during this time
The third trimester is the time of the fastest fetal growth. During this stage, the baby not only grows in size, but every system in his body is finally ready to adapt to the environment of the outside world.
Major growth and changes during this period:
- Weight and fat accumulation: From 28 weeks the baby begins to rapidly accumulate fat which helps regulate his body temperature after birth. During these three months the baby’s weight can increase by almost three times.
- Lung maturation: One of the main functions of the third trimester is to make the lungs self-sufficient. The baby begins to practice breathing during this time and a substance called surfactant is produced that helps him breathe after birth.
- Brain development: The size and complexity of the brain increases dramatically during this time. The baby can now dream react clearly to light and sound, and understand the feeling of pain.
- Bones and muscles: The baby’s bones are now starting to harden but the bones of the skull are soft and separate so that the head can easily pass through the birth canal during delivery.
Baby’s physical abilities
At this time, the baby’s body receives antibodies from the mother, which protect it from infections for the first few months after birth. The baby’s eyes are now fully formed and it can distinguish between light and dark.
Some special aspects of growth
The baby’s hair begins to grow on the head and the fingernails grow to the tips of the fingers. The baby’s skin begins to shed ‘lanugo’ (fine hair) and the ‘vernix’ (white fatty layer) protects the skin.Usually between 32 and 36 weeks, most babies take the head-down position, which is ideal for delivery.
Why are sleep problems increasing?
Sleep problems or insomnia increase in late pregnancy mainly due to physical discomfort and hormonal effects. It becomes difficult to find a comfortable position to sleep due to your growing uterus and it is very normal to feel pain in the back and waist due to the weight of the growing belly. In addition, frequent movements of the baby and the pressure of the uterus on your bladder disrupt your uninterrupted sleep. Mentally, at this time, there is a kind of tension or anxiety in your mind about the responsibility of childbirth and the new baby, which prevents the brain from bringing peace. It is mainly due to the combination of these physical and mental changes that sleep gets away from you in the last months of pregnancy.
Physical and mental causes of insomnia during pregnancy
Although fatigue increases during the day due to changes in the progesterone hormone in your body, not sleeping properly at night is a common problem that affects your mood and energy. Due to the pressure of the uterus, heartburn or acidity often increases, which becomes more difficult while lying down and can lead to leg cramps or ‘restless’ Restless leg syndrome is one of the biggest causes of sleep disturbance. In addition, the baby’s kicks or a sudden nightmare can repeatedly disrupt your deep sleep cycle. Many researchers believe that this insomnia is actually a natural preparation for your body to adapt to the habit of waking up at night after the birth of the upcoming child, which mentally prepares you for the future.
What you can do for better sleep
- Make a habit of turning to your left side when sleeping and use soft pillows between your legs and under your stomach for comfort.
- Reduce the amount of water you drink at least two hours before bed so that you do not have to go to the bathroom repeatedly at night.
- Develop a relaxing habit like taking a warm bath or reading a book before bed, which will give your brain a sleep signal.
- Avoid coffee or caffeinated drinks during the day and choose light and easily digestible foods instead of eating heavy meals before bed.
When do regular checkups become more important?
The importance of regular check-ups increases several times after entering the third trimester of pregnancy because this is when complications like pre-eclampsia or high blood pressure and gestational diabetes are most likely to occur. Although it is generally recommended to visit the doctor once a month for seven months, it is important to check-ups once every 15 days from 28 weeks and every week from 36 weeks until the baby is born.
Aspects that are looked at during the last-minute checkups
Regularly checking the baby’s heartbeat or fetal heart rate to understand any physical pain or distress. Measuring the height of the uterus to see if the baby’s growth is consistent with your pregnancy week. The presence of protein in the urine is checked, which gives an early signal of high blood pressure complications or preeclampsia.The dosage of the necessary medication is adjusted by monitoring swelling of the hands and feet and the level of your physical fatigue or shortness of breath.
Things to be careful about at the beginning of the third trimester
The beginning of the third trimester or around 28 weeks is very important because from this time the body starts making final preparations for delivery. So it is necessary to be extra careful about the following things:
Main precautions:
- Monitoring the baby’s movements: From this time on, the baby’s movements or kicks should be very regular. Count the movements at least once a day at a specific time (usually after feeding). If the baby’s movements seem much less than normal, inform the doctor without delay.
- Avoiding heavy lifting: The ligaments of the waist are loose in the third trimester. Avoid carrying heavy buckets, furniture or small children on your lap. This can put pressure on the uterus or cause injury to your back.
- Avoid standing for long periods of time: Standing for long periods of time can cause blood to pool in the legs, causing swelling in the legs and increasing pain due to pressure on the spine. Rest with your legs elevated between tasks.
- Correct sleeping position: From now on, do not sleep on your stomach. Lying on your stomach puts pressure on the main blood vessels of the body, which can reduce the baby’s blood circulation. Always try to sleep on your left side.
- Raw or undercooked food: Avoid eating open food, raw salads or undercooked eggs/meat completely to avoid infection.
- Stress: Anxiety can increase your blood pressure, so stay calm and think positively as much as possible.
How to prepare mentally
Just as the body prepares for childbirth in the last three months of pregnancy, the mind also needs to be prepared. Mental preparation plays a big role in overcoming fear or anxiety and becoming confident.
Effective ways to prepare mentally are:
- Gaining proper knowledge about childbirth: Having a clear idea about the labor or delivery process reduces fear a lot. Learn about the different stages of childbirth and ways to control pain. However, stay away from watching any scary videos or stories on the internet.
- Sharing fears: If you have any particular fears about childbirth, share them with your spouse, mother or a dear friend. Sometimes, talking about your feelings can reduce half of the anxiety. If necessary, discuss these fears with your doctor.
- Creating a positive environment: Spend time with people who speak positively. Maintain a calm and pleasant environment around you. It is better to maintain a safe distance from those who scare you about delivery at this time.
- Establishing contact with the baby: Start talking to the baby or singing songs to him by stroking his belly. This will not only strengthen your bond with the baby, but also make your mind happy and ready for the baby’s arrival.
Nesting and Relaxation
Tasks like buying clothes for the baby or cleaning the house (called nesting) keep you mentally calm; in addition, practicing deep breathing or breathing exercises for at least 10-15 minutes every day will help relax your nerves.
Some tips to keep your mind calm
- Movies and books: Watch funny or motivational movies and read a good book.
- Small hobbies: Keep yourself busy with small tasks like gardening, writing a diary or drawing.
- Meditation: Meditation or meditation once a day reduces anxiety a lot.
- Self-care: If the body is healthy, the mind is also healthy, so ensure regular light walks and adequate rest.
Does everyone start the third trimester at the same time?
According to the general rules of medicine, pregnancy is divided into three main stages and as such, the third trimester or the last stage is considered to begin from the twenty-seventh or twenty-eighth week, but it does not start on the exact same day for every woman because the calculation of pregnancy depends on the date of your last menstrual period, which may not be completely accurate at times. Depending on the development of the fetus and the hormonal changes in the body, the symptoms of this stage may appear a few days earlier or later in some cases.
Causes and physical effects of differences in the stages of pregnancy
Since each woman’s body and her pregnancy history are different, the feelings of this period also differ. For example, in the case of those who have twins, the discomfort or physical changes of the third trimester may start much earlier, while in many cases, the size and shape of the abdomen may change due to the position of the baby or the location of the placenta. Symptoms like shortness of breath appear late. The effects of hormones work quickly in some people’s bodies, while others may be much more lively. Because of this variation, doctors set a specific week boundary so that your checkups and necessary tests can be completed on time. The main goal of the beginning of this period is to complete the baby’s organs and prepare your body mentally and physically for childbirth, which is considered a completely different and personal experience for every mother.
The differences that may occur at the beginning of this stage
- Depending on the speed of the baby’s weight gain, some people’s stomachs grow very quickly, while others may experience it slowly.
- False labor pains or Braxton Hicks contractions start at twenty-seven weeks for some, while others feel them much later.
- The degree of sleep problems or swelling of the legs due to hormones varies from one body to another.
- The pattern of baby’s movements and kick counts bring differences to each mother’s experience, which is completely normal.
Conclusion
This last stage of pregnancy or the third trimester is the final test of your long wait, where every physical change exposes you to a new experience. Every woman’s journey is different, and the needs of each stage are unique. Have faith in yourself and get through these last days with proper nutrition and positive thinking, because your well-being and awareness will pave the way for a healthy baby to come into the world.


