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3rd Trimester

Patient Education > How the Baby Develops

Third Trimester
28 to 40 Weeks

The Third Trimester of Pregnancy generally spans weeks 28 through 40, though healthy babies may be born a bit sooner or later. Although most women undergo many of the same physical changes during this time, no two pregnancies are alike. OK, is there anything good to say about the third trimester? You don’t like the way you look; you have no self-esteem; all of the excitement of the first trimester has transformed into desperation; even your maternity clothes are tight; and you have the attitude of a 6-year-old on vacation in the back seat of a car saying, “Are we there yet?” Despite all the negatives, one positive still looms large: Soon, you will have a baby!

Trimester Complaints


The enclarged uterus causes a strain on the muscles & ligaments supporting the back resulting in backaces.

Fequent Urination

Urination is frequent because of the growing uterus and the pressing of presenting part ( head or breech ) of the baby on the bladder.

Leg Cramps

Also called night cramps of Pregnancy, these cramps are the result of venous congestion

Shortness of breath

This is due to an overload on circulation. There is also less space for lung expansion because of the uterus pressing on the diaphragm.

Foetal Movements

Baby movements, felt as kicks, become more prominent due to increased weight and larger size of the baby. Others in addition to the above symptoms, you may also complain of sleeping difficulties, constipation, obstructed flow of urine, swelling over feet, itching over stomach, and some of sticky vaginal discharge.

Total Weight gain During Pregnancy

Women of normal weight before pregnancy should gain 8-10 kg

Women who are underweight should gain as much as 10-12 kg

Women carrying twins should gain as much as 12-15 kg

Women who are overweight should gain 6- 8 kg

You’re in the Home Stretch

If pregnancy were a game, you’d be in the last third of a 40-week stretch, heading for the finish line. For the next 12–13 weeks your body will continue to grow and change. Besides the obvious fact that you’re getting bigger in size and dimension, you’re also encountering a few problems due to that size. First, your center of gravity has changed markedly, and it’s more and more difficult to walk and maintain your balance. Second, the swelling of your legs, feet, and hands becomes quite uncomfortable. Be sure to wear comfortable shoes, whether you’re on your feet all day or not. In the evening, try to elevate your feet above the level of your heart. Doing this will help gravity keep the excess fluid from settling in your lower extremities. Take your rings off, if possible, since your hands will inevitably swell, and the rings might be unbearably tight. Third, you simply aren’t sleeping as well. The baby is awake and kicking while you’re trying to sleep (it’s more active in the first half of the third trimester), and you can’t get comfortable to save your life. No sleeping position works very well for any extended period of time—that is, the time it takes to get a decent night’s sleep.

From the beginning of the third trimester until weeks 34–35, you will be going to the doctor once every four weeks. From week 34–37, you’ll start going every two weeks. After that, you’ll visit the doctor once a week.

The doctor will counsel you to do your kick counts on a regular basis. You’ll notice more Braxton Hicks contractions, and it may become hard to differentiate between

false labor and real labor. You may find yourself contacting your doctor more often about those “fake” contractions or going into the hospital to be checked, but likely you’ll be sent home and told to wait. You may notice an increased vaginal discharge, which is probably due to an increase in the amount of cervical mucous that is being produced. The consistency can range from thick to thin and almost watery. Sometimes, women get confused and think that their bag of water has broken when they see this mucous. It hasn’t. Instead, what has probably happened is that the moisture you’ve noticed may actually be urine that has leaked out from your bladder due to direct pressure of the baby’s head on the bladder. The discharge could also be caused by an infection. The way to differentiate is that infections usually have a foul odor and may cause irritation in the vagina. If you’re unsure which it is, mention it to your doctor. If you’re diagnosed with an infection, antibiotics will be prescribed (they are considered safe at this stage of the pregnancy).

To make things even more confusing, there is another type of “discharge” that you might see. If you notice a large pinkish discharge, you may have dislodged the mucous plug. This is a good thing and means that labor is commencing. The mucous plug is the mucous that has been filling the cervical opening and is now dislodged due to the changes the cervix is undergoing as labor progresses. Usually, labor commences within days (if not sooner) of the mucous plug coming out.

Possible Pre-Eclampsia

Although swelling during pregnancy is normal, if you have swelling that is rapid in onset along with elevated blood pressure, then you might have a condition known as pre-eclampsia. Pre-eclampsia is a unique form of hypertension or high blood pressure associated with pregnancy. In the past, doctors primarily used swelling as a marker for the condition. Now, they focus on elevated blood pressures along with excess protein in the maternal urine. However, any excessive and abrupt swelling is not something to ignore and should be reported to your doctor immediately.

If your doctor thinks you might have pre-eclampsia, then the next step is to do serial blood pressure checks (meaning taking the blood pressure repeatedly over a period of time), do a thorough physical exam, and obtain some laboratory tests. If your condition is mild, the doctor may recommend bed rest. However, if you are close to term and have severe pre-eclampsia, the doctor will probably want to induce you. The only cure for pre-eclampsia known today is the delivery of the baby. The exact cause of pre-eclampsia is unknown, although it can occur as early as 20 weeks into the pregnancy. For whatever reason, it’s more common in first-time mothers and women at the extremes of reproductive age (teenagers and women in their late 30s or early 40s).

Inducing Labor

When you hear the term “inducing labor,” it refers to the process by which labor is stimulated by way of medications either placed within the vagina or given intravenously.Inductions are commonly performed when the mother or fetus is at risk or there is a concern that prolonging the pregnancy could put either one of them at risk. Although many women beg to be induced, inductions are not to be taken lightly, because the risks of complications are increased. The main complication, oddly enough, for an induction is a
failed induction. If the induction doesn’t work, then a
c-section must be performed. A c-section exposes both the mother and baby to additional risks, compared to a vaginal delivery, so doctors are generally reluctant to perform an
elective induction. When you are undergoing an induction, be prepared for it to take a long time, by that I mean days. Remember that an induction is an attempt to simulate in a shorter period of time what normally would take days or weeks to occur. Your body simply may be unwilling or slow to kick in.

Using Medicine to Induce Labor

If the cervix is closed when an induction is initiated, the doctor will likely use prostaglandin-based medications placed in the vagina near the cervix. As the medications are absorbed, they have the net effect of “ripening” the cervix, or softening and slowly dilating the cervix. Once this has occurred sufficiently, pitocin is administered through an IV, which has the end effect of stimulating regular, forceful contractions. If your cervix is already dilated, the doctor may proceed to the pitocin stage without the vaginal medications.

Do your part for the baby’s health by observing and recording the kick counts.

Keep drinking that water and elevate those feet anytime you can. Don’t forget to get some exercise—at least walking, so that you’re in shape for the delivery

Be aware of your contractions, so that you can tell the difference between Braxton Hicks contractions (which feel real) and real ones (which feel really, really real).

If you have an inordinate amount of swelling, let your doctor know immediately. Don’t take any risks with your health or your baby’s.

If you can get your doctor to induce you the natural way, go for it. You might as well get this thing over with. The caveat being—your doctor knows best, so if he refuses, know that he has you and your baby’s interests at heart.

Changes in the Foetus

A great deal of growth occurs in the last trimester, although you will notice less during the last month when the growth rate slows down as the mother approaches term. Between 29–33 weeks, the baby will grow to be about 11–16 inches long (the size of a basketball, which is what it feels like inside of you), and weigh anywhere from 3–5 pounds. The next four weeks the baby will experience even more growth from 20 inches to 22 inches long and weighing anywhere from 6–7 1/2 pounds or more.

How the Baby Changes

The third trimester supports continued growth of the fetus, maturation of the organ systems, a change in the amniotic fluid volume, and a change in the baby’s position. The fetus will be adding fat and looking more babylike. All of the organ systems are fully formed. There is a gradual increase in the baby’s ability to breathe on its own as the lungs and nervous system continue to develop. Actually, the lungs are not fully developed until 37–39 weeks. Most of the time, nurseries have very high success rates at taking care of babies born prematurely if they are born after 34 weeks gestation, the main problem being the undeveloped lung system of the fetus. The baby’s eyes are open in utero, and it’s moving around and visibly swallowing. The baby is “breathing” in the sense that its lungs are expanding and the diaphragm is moving up and down (one of the neurological maturation indexes for development).

Actually, the baby is exercising its lungs in anticipation of when it will breathe air. Up to this point, the baby has relied on oxygen in the umbilical cord to meet its needs. The baby will swallow amniotic fluid, which is processed through its digestive system and comes out as fetal urine. That fetal urine is a major component of the amniotic fluid that surrounds and cushions the baby. The fluid will decrease in volume as the baby approaches birth. The fetus that was formerly in a breech position usually will convert to a head-down position as the mother approaches term. Because babies need this time to get to the correct position, it’s common for pre-term babies to have a higher risk of being in the breech position due to their gestational age. For this reason, doctors check the baby’s position carefully when a mother is in pre-term labor.

Kick Counts Continue to Be Critical

The fetal movements that the mother has been experiencing in the second trimester will continue, but it’s normal for the baby to move a little bit less as you approach term due to a couple of factors.

There is less room inside of you, so there is less free space for the baby to move around.

The amniotic fluid has decreased.

Although the baby’s movements may be less frequent, it should still continue to move, and you should continue to monitor the kick counts present.

Monitoring the Amniotic Fluid

The amniotic fluid is essential for the baby’s health and well-being. If the bag of water were to break prematurely, this can precipitate pre-term labor, which can be associated with complications for the baby. Any time a woman thinks she has broken her bag of water, she should report this as soon as possible to a doctor. Not surprisingly, when the bag of water has broken, the amount of amniotic fluid surrounding the baby is decreased. When the amniotic fluid level is low, the baby has a higher chance of lying on its own umbilical cord, which is its lifeline.


When your water breaks, it may come in a gush (in which case it’s evident that it has occurred) or a continual leak (in which case it’s less evident). Typically, water will suddenly gush everywhere, and there is nothing you can do to stop it. You may notice an increase in the amount of pressure in your pelvis and an increase in uterine contactions. When you go to the doctor to have this evaluated, the doctor will test the fluid present in the vagina for the presence of amniotic fluid. He may also do an ultrasound to check the volume of amniotic fluid surrounding the baby. If your bag of water has been broken for a prolonged period of time, you and the baby may develop an infection of the placenta and uterus, characterized by fever, uterine cramping, abdominal pain, and possibly a foul discharge. So this is another reason to go to the hospital when you think your bag of water is broken.

Testing the Placenta

As the placenta becomes more mature, it begins to calcify and may no longer function as well, which typically occurs around the patient’s due date. When this occurs, the placenta becomes less efficient at transporting vital nutrients across its membrane to the baby, and oxygen transport may be affected as well. Women who go past their due date might be asked to begin antepartum testing, which checks to see if the placenta is working well enough for the pregnancy to continue. Although there are different kinds of tests, the nonstress test is the most common. With the nonstress test, a belt is placed around the mother’s abdomen and the fetal heart rate is measured for 20–40 minutes. The doctor will then interpret whether or not the baby is doing well (if adequate oxygenation is present). In addition, the doctor may also request an ultrasound to measure the volume of amniotic fluid that is present. By combining a nonstress test with an ultrasound measurement of amniotic fluid volume, both a short-term and long-term assessment of the baby is obtained. Assuming that these tests are normal, reassurance that the baby will be OK generally
lasts from three to eight days.

The estimated date of confinement (or EDC) is just that—it’s an estimate. When calculating one’s due date, it begins from the first day of the last menstrual period and lasts 40 weeks. The overwhelming majority of babies are born either prior to or shortly after the EDC. The due date should be looked at more as a range between 37–41 weeks, which is considered normal.

While the baby is growing and you can see the obvious outward physical changes, there are a lot of changes occurring internally. Stick to your healthful regimen so that the baby gets all its nutrients.

Although rare, babies can die at this stage for no apparent reason. The best “cure” is prevention. Stay attuned to the baby inside of you and notice any changes in movement, particularly if it is decreased. Report them to your doctor
immediately or get to a hospital.

Rely on your own judgment to determine the condition of your baby, rather than friends’ opinions. If you have a question about your medical condition, never hesitate to call your doctor first.

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