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The Third Trimester of Pregnancy: Weight Gain and Other Changes

The 3rd Trimester of Pregnancy

The third trimester of pregnancy produces the most rapid changes for your baby. At the same time, your body will go through significant changes to support your growing fetus. Some of these symptoms are often experienced during the first and second trimesters, but they are often worse as you near the end of your pregnancy.

Rapid Weight Gain

Now that you have reached the third trimester, you are literally in the final stretch. During the final months of pregnancy, your baby puts on the most body weight. In fact, according to the American Pregnancy Association, a fetus weighs just 4 pounds at 27 weeks, but will grow to 6 ¾ pounds to 10 pounds by the time you go into labor. Your baby will also grow an average of four to six inches long during the third trimester.

In addition to baby weight, your body will also gain weight from:

  • fat stores
  • fluids
  • more blood
  • amniotic fluid
  • a larger uterus
  • the placenta

All of these additions will come with a few extra pounds — this is one reason why doctors and midwives stress that women try not to gain too much weight during the first two trimesters of pregnancy.

While you certainly don’t want to lose weight during the third trimester, it’s also important to not cave in to those food cravings and to remain as active as possible. This will help you prevent unnecessary weight gain. The total amount of weight you should gain depends on how much you weighed pre-pregnancy. Complications of too much weight gain can show up during the third trimester, and may include:

  • premature birth (baby is born at 37 weeks or earlier)
  • gestational diabetes
  • high blood pressure
  • baby is born large

Leg Veins and Swelling

Natural weight gain from pregnancy can also cause swelling of your legs and ankles. The problem can be worse with extra fluid retention, so make sure to drink plenty of water and avoid salty foods. Spider veins and varicose veins may also develop because of the extra pressure in your lower extremities. Take pressure off of your legs when you can. You may also consider using support stockings if the swelling is causing pain.

Minor fluid retention is normal, but rapid and painful swelling in your legs and ankles could be a cause for concern. Tell your doctor about any sudden swelling, so they can rule out preeclampsia — this is a life-threatening condition marked by extremely high blood pressure and the presence of protein in the urine.

Breast and Vaginal Changes

The third trimester is marked by preparations for labor, so it’s natural to see some notable breast changes. Whether you have decided to breast feed or bottle feed your baby, it’s normal for breasts to grow larger and more tender during the final weeks of pregnancy. In fact, the Mayo Clinic estimates that women gain an average of 2 pounds of tissue in the breasts during pregnancy. By the third trimester, your breasts may also leak colostrum, which is pre-breast milk that is yellow in color.

During pregnancy, any significant vaginal changes could be a cause for concern. The small exceptions are the changes that occur during the third trimester. As you near the end of your pregnancy, you may notice some vaginal discharge. This is a result of a softening cervix that helps the rest of your body prepare for labor. You should call your doctor if you notice excessive discharge; a discharge that has a thickened, yellow, green, or cheesy quality, since this might indicate an infection; or any blood from the vagina.

Aches and Pains

Your growing baby is starting to get cramped in your belly, so you might start feeling more kicks and other movements. Some of these might be painful from time to time—perhaps your baby is a future soccer star! A growing fetus can also mean more body aches for you because of the extra weight you’re carrying. Aches and pains in the back, knees, and neck are common during the third trimester. Rest and put your feet up when you can, and alternate between ice packs and heated pads to alleviate the pain.

Frequent Urination

During the first and second trimesters, you might have experienced increased urination due to hormonal changes. Now that you’re in the third trimester, it may seem like you have to go every hour — this is because all of the weight your baby is gaining is putting extra pressure on your bladder. Avoid drinking too many fluids at night to avoid sleep disruptions.

Aside from the annoyance of frequent bathroom visits, this isn’t usually a cause for concern. However, if you also notice any blood in your urine or experience back pain, call your doctor right away — these could be signs of a urinary tract infection.

Trouble Sleeping at Night

Early pregnancy is marked by increased fatigue. This still may be true for your pregnancy, but you are more likely to experience insomnia during the third trimester. Whether you wake up from bathroom visits, or your baby decides to be alert and kick at night, general discomfort is the primary reason why pregnant women can’t sleep at night. The best you can do is to make sure you prepare yourself and your bedroom for a good night’s sleep. Make sure you:

  • avoid exercise in the late afternoon and evening
  • keep your bedroom cool and dark
  • avoid late naps
  • layer your bedding in case you get hot
  • take a warm bath before bed
  • meditate or engage in deep breathing exercises
  • use extra pillows to support your belly

Other Changes

Some mothers-to-be experience other changes during the third-trimester, including:

  • heartburn
  • hemorrhoids
  • shortness of breath
  • belly button sticking out
  • Braxton Hicks contractions (these are weak and are not the same as labor contractions)

Final Preparations for Baby

Perhaps the most significant changes you will experience towards the end of your pregnancy are contractions. Unlike Braxton Hicks contractions, these are progressively strong and happen closer and closer together. Congratulations — this is your cue to call your doctor to prepare for the arrival of your baby!

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