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Third trimester of pregnancy

Third trimester of pregnancy


The third trimester includes the 7th, 8th and 9th months of pregnancy. This is the period from the 29th to the 40th week with the obstetric method for calculating the gestational age.

Although the normal duration of pregnancy is 280 days or 40 obstetric weeks, the delivery that occurred at 38–42 weeks is also within the norm. A baby born at the 37th week or earlier is considered premature, and after the 42nd week – overdue.

What happens to mother’s body during third trimester?

The third trimester marks the final stretch for both mom and baby, as the most challenging months have passed. A pregnant woman’s body is readying itself for delivery, and some of the signs of pregnancy, such as anticipation of the baby’s arrival, have already become familiar. Others, however, may only now become evident and require medical attention.

Here are some things that a woman will experience during pregnancy in the third trimester:

  • Edema.
  • Isolation of colostrum.
  • Augmentation of the abdomen and breasts.
  • Frequent urination.
  • Seizures.
  • Vaginal discharge.
  • Enlargement of veins.
  • Moderate joints and lower back pain.
  • Feeling the movements of the child.
  • Training contractions (Brexton-Hicks contractions).

Edema: In the third trimester, swelling is most pronounced. A pregnant woman’s body builds up amniotic fluid in preparation for childbirth and retains fluid to make breast milk. The doctor examining a patient with swelling must rule out preeclampsia and other potential risks to both the patient and the unborn child. This is because the increased content of the hormone progesterone in the blood prevents water from being excreted worse, which is normal for expectant mothers.

Isolation of colostrum: Peak production of immature breast milk occurs in the third trimester, especially in the weeks leading up to delivery. This phenomenon is due to the action of the “hormone of motherhood” – prolactin. 

Weight set: The approximate rate of weight gain in the third trimester is 5–8 kg. Generally, this norm for the expectant mother is determined by the doctor observing the pregnancy, considering various parameters. 

Augmentation of the abdomen and breasts: The proportions of the expectant mother’s body continue to change: the breasts increase, preparing for feeding, and the stomach significantly increases in volume, as the baby itself and the organs that ensure its vital activity grow. 

By the end of the third trimester, the baby weighs an average of 3000-3500 g, the uterus – at least 1000 g, the placenta – 700-900 g. Amniotic fluid volume also reaches a maximum of 1-1.5 liters. You still need to pay attention to the hydration of the body’s skin to minimize the severity of stretch marks. 

Shortness of breath: The enlarged uterus puts pressure on the diaphragm, prevents the lungs from expanding, and it becomes difficult for the expectant mother to breathe deeply. 

Frequent urination: For the third trimester, this is the absolute norm. A large uterus presses on the bladder, which provokes an increased urge to empty it. In addition, the woman’s kidneys work in an enhanced mode, because they also need to remove the waste products of the child. The hormonal background also affects, due to which the bladder’s walls are so relaxed that even slight urinary incontinence is possible when laughing, or coughing. 

Seizures: Sharp spontaneous contractions of the muscles of the legs, arms and neck in the third trimester bother pregnant women more often than in the 2nd. The reasons for this are different: from vitamin deficiency and anemia to the syndrome of compression of the inferior vena cava, varicose veins and diseases of a woman’s internal organs, so she needs a doctor’s consultation. 

Vaginal discharge: Milky white discharge (if it is not thrush) is considered normal and caused by hormonal changes. By the end of pregnancy, their volume will increase under the influence of estrogen, and the consistency will become more watery. Brown, green and brownish-yellow discharge is an alarming symptom, possibly indicating placenta previa, urinary tract infections. This is an important reason to visit a doctor and find out everything.  

Enlargement of veins: The veins become noticeably pronounced, a feeling of heaviness appears in the legs, and 20–40% of women develop varicose veins during the 2nd–3rd trimester. An increase in the volume of blood and body weight of a pregnant woman, a change in the hormonal background and the squeezing of organs, tissues and veins in the abdominal cavity by a heavy uterus leads to problems with veins. A future mother should visit a phlebologist. 

Moderate pain in the joints and lower back: Caused by an increase in mass and a change in the center of gravity of the expectant mother’s body, the load on her knees and spine increases significantly.

Feeling the movements of the child: The larger and older the baby, the more noticeable his movements: kicks, pushes, somersaults. The peak of his activity falls during the evening and night hours, often preventing the mother from fully resting and getting enough sleep. The fetus reaches its final position in the uterus at 35-37 weeks, becoming too large to move around in the mother’s belly. This usually causes little worry.

Training contractions (Brexton-Hicks contractions): Due to the body’s preparation for childbirth. The hormonal background of the future mother is changing again: the production of progesterone is reduced, and the female hormone – estrogen – is growing. Estrogen contributes to the gradual opening of the cervix, increases its tone, resulting in training contractions, irregular and usually painless.

Baby at third trimester Ultrasound at third trimester
Baby at third trimester Ultrasound at third trimester

What happens to the baby in the third trimester?

From the 28th week, doctors call the future little man, who will be born about three months later, no longer a fetus, but a child.

If a baby is born between 22 and 37 weeks prematurely, they will likely survive with proper care. As long as there are no severe developmental issues, they will remain healthy and their development should not be delayed compared to other children.

7th month: The baby’s stomach, intestines, kidneys and liver are ready for his life outside the mother’s body, but the lungs are not yet. Baby makes training breathing movements, and a special substance – surfactant – does not allow the lungs to subside when exhaling.

Your child’s pancreas produces its insulin, which regulates blood sugar levels. The nervous system increases the number and depth of the convolutions of the cerebral cortex. The baby has developed hearing, taste, and touch. The baby recognizes his mother’s voice and “understands” her intonations.

The baby reacts emotionally to what baby likes / dislikes or what scares him. The baby is actively pushing and changing positions; his body proportions are approaching the proportions of a newborn. However, baby is gaining weight no less actively, so very soon, baby will feel cramped in his own “house”.

8th month: The baby develops its mode of sleep and wakefulness, which does not always coincide with the mother’s. It is becoming more and more difficult for him to move in his mother’s stomach, and the activity of the crumbs is felt as sipping or turning from side to side.

By the end of the month, baby takes the position in which baby will be ready to be born (head presentation is the norm). The baby’s nervous, endocrine, and immune systems have seen further improvement. The vellus hair on its body is beginning to disappear and the nails on its fingers have fully grown, covering the nail bed.

The baby’s swallowing, sucking and respiratory reflexes are already so developed that in case of premature birth baby will be able to breathe and suckle on his own. At the end of the month, the child’s height is 44–48 cm, and the weight is 2400–2700 g. 

9th month: Your baby is ready to be born. Once born, baby can breathe on his own, suckle and absorb his mother’s milk. If the baby did not assume the prenatal position in the previous month, the head or, less commonly, the buttocks of the child are now pressed against the entrance of the mother’s small pelvis.

The motor activity of the baby is diminishing, making it difficult for them to move around. As the third trimester progresses, the baby accumulates subcutaneous fat which in turn causes the vellus hair, or lanugo, to vanish, making the skin softer and more elastic. Nails on the hands and feet grow to full length, covering the nail bed. 

In boys, the testicles descend into the scrotum (this can happen a month earlier and sometimes after birth). In girls, the small labia are covered with large ones. Improving immune, cardiovascular, respiratory and nervous systems. At the end of the month, the child weighs an average of 2500-5500 g with a height of 45 to 55 cm. 

Third trimester with twins

The third trimester is the shortest and therefore the most exciting in multiple pregnancies. What should a future mother of two babies be aware of and what to prepare for twins? 

  • After the 28th week of pregnancy, you need to visit the antenatal clinic once every 7–10 days.
  • The calorie content of a pregnant woman’s diet with the recommended 5-6 meals a day should be at least 3500 kcal/day.
  • The total twins third trimester weight gain from the beginning of the 1st to the end of the third trimester should be at least 18–22 kg.
  • In the second and third trimesters, prophylactic iron supplementation is mandatory (as prescribed by a doctor) since almost 100% of pregnant twins develop iron deficiency anemia.
  • The pregnant mother of twins has more intense symptoms such as frequent urination, weight gain, constipation, anemia, shortness of breath, heartburn, back and joint pain, swelling, varicose veins, sleep disturbances and false contractions.
  • Preeclampsia, also known as late toxicosis, occurs in 45% of women with multiple pregnancies. Expectant mothers of multiples may experience more difficulty than those expecting a single baby due to the larger placental mass, which is also known as hyperplacental disease.
  • In grown-up babies, the strength of the pushes is added, but the amplitude of movements decreases: they are already cramped inside their mother’s bellies.
  • By the end of the third trimester, both babies reach about 35-45 cm in length and weigh about 2200-3000 g each.
  • Premature birth is the norm in multiple pregnancies. As a rule, Twins are born at 36–37 weeks, although there are cases when typically developing babies are born earlier, at 28–35 weeks.
  • To prevent premature birth, doctors recommend a protective regimen for expectant mothers twice: restriction of physical activity, mandatory rest of 1-2 hours three times a day and other preventive measures.
  • When choosing the tactics of childbirth, the doctor takes into account the intrauterine position of the twins: before birth, babies in the mother’s stomach can be located both heads down, both heads up, one head up, the other down, one vertically, the other horizontally, both horizontally.
  • Twin pregnancy is not an absolute indication for cesarean section: the doctor may recommend, taking into account, the health of the expectant mother and the development of her babies, and natural delivery.
  • Indications for a planned cesarean section with twins are the total weight of babies of 6000 g or more, polyhydramnios, weak labor activity, prolapse of umbilical cord loops during the head presentation, acute hypoxia of both or one of the babies, placental abruption, etc.
  • In most cases, childbirth during multiple pregnancies involves the woman in labor lying on her side to avoid compression of the inferior vena cava syndrome.

Danger signs of pregnancy in third trimester

Your body has been the best “home” for the baby for more than six months. The observation of doctors and the implementation of their recommendations will help to safely bring the baby to childbirth and overcome the complications that arise in late pregnancy.

Here are pregnancy complications and danger signs of pregnancy in third trimester:

  • Late toxicosis.
  • Fetal growth retardation syndrome (FGR) + placental insufficiency.
  • Placental abruption.
  • Placenta previa.
  • Premature aging of the placenta.
  • Increased tone of the uterus.
  • Oligohydramnios/polyhydramnios:.
  • Premature birth.

Late toxicosis: Approximately 7-16% of pregnant women experience late toxicosis during pregnancy, which differs from the malaise commonly experienced during the first trimester. 

It is manifested not only by nausea and vomiting (these signs may not be) but also by severe edema (not only the face and body swells but also internal organs, including the uterus and placenta), migraine, dizziness, worsening sleep and other symptoms. 

The most serious risks of pregnancy are preeclampsia and eclampsia. Preeclampsia is a condition of high blood pressure and proteinuria, which is the excretion of protein in the urine in amounts greater than normal and indicates kidney damage in pregnant women. Eclampsia is a complication that can develop from preeclampsia and leads to convulsions.

Preeclampsia and eclampsia occur after 20 weeks of pregnancy in 3-7% of expectant mothers. Late toxicosis is dangerous for the health and life of the mother and child. Therefore, it requires the supervision of a doctor and often hospitalization. 

Fetal growth retardation syndrome (FGR) + placental insufficiency:  A common pathology found in the second and third trimesters is intrauterine growth retardation (fetal hypotrophy) caused by placental insufficiency. Hypotrophy can be symmetrical when all the organs of the child are evenly reduced and asymmetric when the brain and size of the baby correspond to the gestational age and the internal organs lag in development.

A deterioration in uteroplacental blood flow causes FGR: with an insufficient supply of oxygen and nutrients through the placenta, hypoxia develops – the baby starves and suffocates. A variety of reasons can provoke a deterioration in blood flow between mother and child.

Bad habits and infectious diseases, late toxicosis, high/low blood pressure, anemia, kidney disease, diabetes mellitus, as well as the age of the woman (less than 18 and more than 35 years), genetic abnormalities of the baby, multiple pregnancies. FGR is treatable; therefore, the child will be born healthy with its timely identification and adjustment.

Placental abruption: The placenta also known as the placenta, a child’s place, is a temporary cake-like organ made of connective tissue that forms inside the uterus by the 15-16th week of pregnancy and serves to connect the mother and child’s organisms providing the baby with everything necessary. Premature separation of the placenta from the uterine wall can occur both during labor and during the period of gestation. According to statistics, this happens in 1 out of 120 pregnancies. 

Third trimester bleeding: The causes of detachment are preeclampsia, arterial hypertension, polyhydramnios, multiple pregnancy, and other factors. Symptoms – uterine hypertonicity, abdominal pain, uterine and vaginal bleeding, and disturbances in the baby’s cardiovascular system. If the area of ​​the placenta detached is less than 25%, the baby can be born safely without any danger to its health.

If more than 30% of the placenta detaches from the surface of the uterus, it can be very dangerous for the mother and baby. This can lead to severe internal bleeding and deprive the baby of oxygen and essential nutrients. Urgent surgery is required, and in the second half of pregnancy, most likely, doctors will resort to a cesarean section (C section).

Placenta previa: The place of attachment of the placenta is of great importance. The “children’s place” moves up inside the uterus as the baby develops. If, after the 32nd week of pregnancy, the placenta remains down, blocking the child’s exit from the uterus (uterine os), this is called presentation. Pathology can manifest through uterine bleeding in the 2nd or third trimesters and is considered an indication for caesarean section. 

Premature aging of the placenta: After the 36th week of pregnancy, the placenta begins to gradually die off, as the child is already formed and viable. If the aging of the “children’s place” begins earlier than this period, medical treatment or, if there are indications, stimulation of labor activity is necessary. Pathology is detected using conventional ultrasound and Doppler ultrasound – a special ultrasound that can diagnose a violation of blood flow in the vessels.

Increased tone of the uterus: Tension and involuntary contractions of the muscular walls of the uterus, leading to incomplete disclosure of its neck, are called hypertonicity. In late pregnancy, the tone of the uterus is the norm – this is how the body prepares for childbirth, arranging rehearsal contractions.

Drug therapy and medical supervision is required if hypertonicity appears before the 37th week and greatly affects the well-being of the expectant mother, accompanied by bloody or watery vaginal discharge, nausea and vomiting. For a child, hypertonicity is dangerous for the development of hypoxia – a lack of oxygen and nutrients caused by spasms of the uterus blood vessels. The causes of increased tone are physical overload, stress, infectious diseases and inflammatory processes, bad habits,

Oligohydramnios/polyhydramnios: Lack or excess of amniotic fluid – amniotic fluid – is unfavorable for the baby. However, doctors believe that moderate oligohydramnios in the third trimester is not so dangerous for the baby. The amniotic fluid index (AFI) is calculated based on ultrasound data.

For example, at the 36th week it is 138 mm (the distance between the uterus and the anterior abdominal wall) with an allowable range of 68 to 279 mm. On the eve of childbirth, there should be no more than 1.5–2 liters of amniotic fluid in the expectant mother’s uterus. If the volume of amniotic fluid significantly differs up / down from the IAI recommended for a particular week of pregnancy, oligohydramnios/polyhydramnios is diagnosed. 

It can cause placental abruption, infection of the urinary tract, abnormal position of the fetus in the uterus (for example, breech presentation), hypoxia of the child, disorders in the development of its nervous and digestive systems, and premature and complicated births. 

Infectious diseases, inflammatory processes, chronic diseases of the kidneys and the cardiovascular system, arterial hypertension, bad habits and malnutrition of the expectant mother, and Rh-conflict of her body with the child provoke a deficiency or excess of amniotic fluid. Oligohydramnios can also be a symptom of amniotic fluid leakage that is unsafe for the baby. Doctors must be supervised to ensure the health and safety of the mother and baby are maintained and the delivery is successful.

Premature birth: These births occurred from the 22nd to the 37th week. Their causes are placental abruption, hormonal imbalance, multiple pregnancies, bad habits of a woman, urinary infections, preeclampsia, isthmic-cervical insufficiency, anemia, severe stress, weight lifting and other factors.

Symptoms of preterm labor: painful contractions that recur at regular intervals, bloody or watery discharge, upset stool (diarrhea), menstrual cramps, and pain in the lower back and groin. If there are more than 4-5 contractions per hour, you need to call the doctor who is observing you and be ready (have a pre-assembled bag with things and documents) to be sent to the maternity hospital.

Do’s and don’ts for third trimester

What to do in your third trimester of pregnancy?

  • At the end of pregnancy, it is recommended:
  • Give up smoking as well as the use of alcohol and drugs. 
  • Get 8-9 hours of sleep each night. Eat regularly and eat healthy.
  • Always wash your hands to prevent the spread of infectious diseases.
  • Avoid overworking and stressful situations.
  • Consult your doctor before taking any multivitamins and supplements.
  • Wear compression stockings to prevent varicose veins, and remove them when resting or sleeping.
  • Put on a bandage if necessary.
  • Sleep on your left side, and use a separate pillow for your stomach.
  • Ask your doctor about taking a massage course.
  • Exercise regularly but gently, such as walking, pregnancy-friendly gymnastics, swimming, and aqua aerobics.
  • Do Kegel exercises to avoid urinary incontinence and tears during childbirth.

What not to do in your third trimester of pregnancy?

  • Take any medications without your doctor’s approval. 
  • Strenuous exercise. 
  • Wear comfortable, loose clothing, underwear and shoes, high heels.
  • Undergo x-rays. 
  • Have sex if there is a threat of preterm labor, placenta previa, multiple pregnancies and other risk factors.
  • Sleep on your back. 
  • Lift weights over 3 kg. 
  • Drink more than 1.5 liters of fluid per day (excess in the body increases swelling). 
  • Visit a sauna, bath or take hot baths (at a water temperature above 37 degrees). 
  • Dye your hair. 
  • Fly by plane (starting from the 7th month of pregnancy).

Third trimester nutrition

The third trimester is when the baby is most actively gaining height and weight. Therefore, the expectant mother should feed him and herself varied and useful, but not plentiful, to avoid weight gain, digestive problems and the development of a large child. It would be useful to coordinate the diet with the doctor, especially if there are food allergies or chronic diseases.

The basic principles of a healthy diet in the third trimester are as follows:

  • Daily caloric intake with the recommended 5–6 meals a day should not exceed 2500–3000 kcal (the frequency of meals can be increased to 8 meals per day by reducing the size of portions).
  • The last meal 2 hours before bedtime – a glass of kefir or warm milk.
  • depending on the tendency to edema, the volume of daily absorbed liquid, including soups, tea, juices, fruit drinks, kefir, etc., should be from 0.8 to 1.5 liters, and salt – up to 5 g, since it helps to retain water in the body.
  • It is better to limit caffeinated drinks such as tea and coffee and replace them with healthier alternatives like chamomile tea, fruit drinks, jelly, and compotes. Caffeine can increase vascular tone, raise blood pressure, remove calcium from the body, and promote dehydration.
  • It is advisable to prepare meals for a couple using methods such as stewing, boiling, or baking in the oven and to limit fried foods as much as possible.
  • Eat fruits, vegetables, dairy products, whole grain bread, pasta, lean meats, poultry, fish, eggs, cereals, vegetables and butter.
  • During third trimester limit consuming milk, legumes, curd cheeses, semolina, sugar, white bread, pastries, sweets, sweet juices, exotic fruits, honey, cocoa, chocolate, and fish caviar.

Third trimester checklist

  1. Complete scheduled examinations and tests 
  2. Read literature about newborn care, parenting
  3. Learn about a birth certificate.
  4. Choose a place for childbirth, and decide on their budget.
  5. Decide on the name of the baby.
  6. Collect a bag for the maternity hospital with the necessary things, documents and an exchange card for a pregnant woman
  7. Decide if you need the presence of an assistant in childbirth: husband, mother, girlfriend, doula 
  8. Consider whose help you can enlist in the first weeks and months when the baby is born
  9. Discuss a tentative pregnancy plan with your doctor, particularly your views on cesarean section, water birth, home birth, epidural anesthesia, etc.
  10. Arrange for maternity leave, study what single and long-term payments you are entitled to and how to get them (institutions you need to apply to, a package of documents, etc.) 
  11. During the third trimester arrange a grand shopping and replenish the home supply of non-perishable food, hygiene products, household chemicals, and medicines, buy the missing baby dowry items so that after returning from the maternity hospital, you do not need frequent trips to shops and pharmacies
  12. Make a creative gift for a future baby: buy a paper or create an electronic (examples and templates are on the Web) album of a newborn, where to put, for example, a photo of your tummy at a later date, your impressions and experiences in the days of waiting for the crumbs, expressed in the form of diary entries, and then – information about the first days, weeks and months of the life of a son or daughter after birth

Helpful tips for third trimester

Find ways to gently soothe your baby when his movements are too painful for you:

From experience, many expectant mothers in third trimester are helped by a shower or bath with warm water, walking for several minutes on all fours around the room or a simple short walk, gentle self-massage of the abdomen. 

Make your list of necessities for the hospital:

There are many lists of what women take with them to the hospital. During third trimester Review the lists of items, interview mothers in your vicinity to understand what was helpful and unnecessary during their stay in the hospital, and use this information to form your own clear idea of what to bring in your bag for the maternity hospital, in addition to the required documents.

Learn Kegel exercises:

Discuss with your doctor if you have any contraindications, and if the specialist does not object, start doing exercises to strengthen the pelvic floor muscles. These exercises help in normalizing the number of urination and preventing urinary incontinence in labor, as well as in restoring the quality of intimacy after childbirth. And Kegel exercises are one way to calm the fidget in your stomach.