The Third Trimester

Prenatal visits during the third trimester

During the second and third trimester prenatal visits, your health care provider may check the following, depending on your current medical condition and the health of the fetus:

  • any current symptoms or discomforts
  • your weight
  • your blood pressure
  • urine test to detect albumin (a protein), which may indicate preeclampsia or toxemia, and sugar, which may indicate hyperglycemia
  • position, growth and development of the fetus
  • height of the fundus (top of the uterus)
  • fetal heartbeat

As you begin the third trimester, your health care provider may change the schedule of your prenatal visits from monthly to every two weeks. Your prenatal visits may be scheduled once every week in the last month. This schedule will depend on your medical condition, the growth and development of the fetus and your health care provider’s preference.

Toward the later weeks of the pregnancy (beginning at approximately the 38th week), your health care provider may perform a pelvic exam to determine the dilation and effacement of your cervix. He or she will also ask about any contractions and discuss labor and delivery procedures.

What to expect during the third trimester

The third trimester marks the home stretch, as the mother-to-be prepares for the delivery of her baby. The fetus is continuing to grow in weight and size, and the body systems finish maturing. The mother may feel more uncomfortable now as she continues to gain weight and begins to have false labor contractions (called Braxton-Hicks contractions).

During the third trimester, it is a good idea to start taking childbirth classes in preparation for the big day — especially in the case of first pregnancies. If you plan to breastfeed, taking a breastfeeding class may be helpful.

During the third trimester, both the mother's body and fetus continue to grow and change.

Fetal development during the third trimester

During the third trimester, the fetus continues to grow in size and weight. The lungs are still maturing, and the fetus begins to position itself head-down. By the end of the third trimester, the fetus is about 19 to 21 inches long and weighs, on average, 6 to 9 pounds. During the third trimester:

  • The fetus can see and hear.
  • The fetus’s brain continues to develop.
  • The kidneys and lungs continue to mature.
  • By the 36th week, the head may engage (drop into the pelvic area), which is a process called lightening.
  • The bones of the skull remain soft to make it easier to pass through the birth canal.
  • For many babies, the irises of the eyes are slate blue. The permanent eye color will not appear until several days or weeks after birth.
  • The fetus can suck its thumb and has the ability to cry.
  • By 38 to 40 weeks, the fetus's lanugo has disappeared almost completely.
  • By 38 to 40 weeks, the lungs have matured completely.
  • The baby is covered in vernix caseosa (or simply called vernix), a creamy, protective coating on the skin.
  • The head will usually turn downward during the last couple of weeks of pregnancy.

Changes in the mother's body

In the third trimester, some women become increasingly uncomfortable as their due date nears. As the fetus grows in size and crowds the abdominal cavity, some mothers-to-be have difficulty taking deep breaths or getting comfortable at night for sleep.

The following is a list of changes and symptoms that a woman may experience during the third trimester:

  • Skin temperature increases as the fetus radiates body heat, causing the mother to feel hot.
  • The increased urinary frequency returns due to increased pressure being placed on the bladder.
  • Blood pressure may decrease as the fetus presses on the main vein that returns blood to the heart.
  • Swelling of the ankles, hands and face may occur (called edema) as the mother continues to retain fluids.
  • Hair may begin to grow on a woman's arms, legs and face due to increased hormone stimulation of hair follicles. Hair may also feel coarser.
  • Leg cramps may become more frequent.
  • Braxton-Hicks contractions (false labor) may occur at irregular intervals in preparation for childbirth.
  • Stretch marks may appear on the abdomen, breast, thighs and buttocks.
  • Colostrum (a fluid in the breasts that nourishes the baby until the breast milk becomes available) may begin to leak from the nipples.
  • Dry, itchy skin may persist, particularly on the abdomen, as the skin continues to grow and stretch.
  • A woman's libido (sexual drive) may decrease.
  • Skin pigmentation may become more apparent, especially dark patches of skin on the face.
  • Constipation, heartburn, and indigestion may continue.
  • White-colored vaginal discharge (leukorrhea) increases, which may contain more mucus.
  • Backaches may persist and increase in intensity.
  • Hemorrhoids may persist and increase in severity.
  • Varicose veins in the legs may persist and increase in severity.

As demonstrated above, each woman carries her baby differently, depending on her body structure and amount of weight gain.