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What Is the Third Trimester of Pregnancy?

The third trimester of pregnancy encompasses weeks 28 through 40 of your pregnancy. From week 37 onward, doctors consider your baby full term, so you know she will be arriving soon. Those few weeks may seem longer than the rest of your pregnancy combined! Understanding what to expect during the last part of pregnancy can help lessen your anxiety and help you look forward to your baby’s birth.

What Happens to Your Body During the Third Trimester?

Obstetrician Visit for Pregnant Woman in Third TrimesterAlthough you may be tired of being pregnant, it is important to remember that every week brings you closer to seeing your baby in person! It is also important to bear in mind that for each week she stays inside you, the better prepared she will be for life on the outside.

27-32 weeks

  • The top of your uterus now sits about five inches above your belly button. This may put pressure on your diaphragm, increasing your heartburn and making you feel short of breath.
  • You are probably gaining about one pound every week, and your blood volume has increased by 40 to 50 percent. This increased volume is needed to support both you and your baby.
  • You have probably been seeing your obstetrician once a month, assuming there have been no complications during your pregnancy. Sometime during your final trimester, the doctor will start seeing you every two weeks, and then every week as your due date approaches.
  • You may experience more swelling in your feet and ankles, as well as more aches and pains in general. Carrying around a baby in your belly can be hard work, and it puts pressure on blood vessels, tendons and ligaments.
  • You may also feel some anxiety about labor and delivery. This is normal, and your doctor or childbirth class instructor can help reassure you.

38 to 40 weeks

Your baby should turn head-down by this point in your pregnancy. If not, he is in what is called a breech. If this happens, the doctor may recommend another sonogram to confirm the baby’s position. A breech delivery can be more complicated, and your doctor may want to talk to you about your delivery options.

The obstetrician may recommend a non-stress test during the final weeks of your pregnancy, too. The test just monitors the baby’s heart rate and movements when he is not under the stress of labor.

Pregnant Woman Having Trouble Sleeping During Third Trimester

Other normal body changes in your third trimester include:

  • More Braxton Hicks contractions. As long as these are random and not occurring on a schedule you can time, there is no reason to worry.
  • Increased urination as the baby grows and presses on your bladder.
  • Hemorrhoids, as the baby grows and puts more pressure on blood vessels in your lower body.
  • Difficulty sleeping as your belly grows.
  • Tender breasts, and watery milk beginning to leak from your breasts.

Pregnant Woman in Third Trimester Experiencing Braxton-Hicks ContractionsCall your obstetrician immediately if any of the following occur:

  • Contractions that become regular in frequency, increase in frequency or intensity, or become painful.
  • Vaginal bleeding
  • Sudden decrease in baby’s activity
  • Extreme swelling of your face, legs, feet, ankles or other body parts
  • Rapid or excessive weight gain

Tips for Mom’s Partner During the Third Trimester

Your baby is nearing delivery, so it is important to give some thought to a few important questions in the final months of preparation:

  • Do you want to be present for the baby’s birth? If you travel for work, this may take some planning.
  • How will you ensure you make time for your new baby and your partner after the baby arrives? They will both need your support.
  • What do you want life to be like once the baby is born?
  • Can you arrange for parental leave?
  • How is the baby budget doing? Do you need to put a little more aside to make sure things go well?

What Can You Do to Prepare for Birth During the Third Trimester?

You have probably already decided where to give birth to the baby. If not, now is the time to do this and to tour the birthing facility. Familiarize yourself with their check-in procedures, their birthing rooms and the nurses, if you can. Take a tour of the nursery, too!

If you and your partner have not attended childbirth classes, do this now! This is your chance to learn what to expect during labor and delivery, as well as to find out about options available to you during delivery. You will also get to ask questions of experienced labor and delivery coaches, learn to diaper and breastfeed your new baby, and get valuable resource information that you will need after your baby arrives.

A checklist of things to have ready before baby arrives:

  • A family member or friend on standby to care for pets and other children.
  • A bag packed and ready for the hospital for yourself, your partner and the baby.
  • The practiced route to the hospital and the mode of transportation to get there.
  • An approved car seat installed in your car – and practice using it!
  • Maternity leave arranged with your employer, and parental leave arranged for your partner.
  • A crib set up for baby and double-checked for safety, especially if it is used or a hand-me-down.
  • Emergency numbers written down and close to your phone – for your emergency child care provider, pet sitter, and yourself if you need to call your doctor.
  • Stocks of baby supplies like diapers, baby wipes and baby clothes in newborn and infant sizes obtained.
  • Have baby’s room set up and decorated, including a nursing rocker and footrest for yourself!
  • Check any used or hand-me-down equipment such as strollers and car seats to make sure they meet government safety standards.
  • You have made a birth plan with your obstetrician, including who will be with you during labor and delivery, concerns you may have about procedures at the hospital, hospital pre-registration completed with your insurance information, plans for nursing your baby, and your preferences regarding anesthesia during labor and delivery.
  • Celebrate your baby’s pending arrival with your friends and family!

Fetal Development in the Third Trimester

Third Trimester, Week 28 Gestational Age (Week 26 Fetal Development)

Your baby’s brain is developing billions of neurons. Her eyelids can partially open, and she has eyelashes. She may have dreams, too. Her eyesight is getting better. Her central nervous system can control her breathing movements and her body temperature. She probably weighs about two and ¼ pounds and measures around 15 inches from head to foot.

Third Trimester, Week 29 Gestational Age (Week 27 Fetal Development)

Your baby kicks, stretches, and makes grasping movements with his hands. You feel him moving inside you frequently.

Third Trimester, Week 30 Gestational Age (Week 28 Fetal Development)

Baby can now open her eyes completely, and she may have a full head of hair. Her bone marrow is forming red blood cells. She has grown to weigh almost three pounds.

Third Trimester, Week 31 Gestational Age (Week 29 Fetal Development)

Your baby has finished most of the major developments – his organs and bones are all in place. Now he will start putting on weight quickly in preparation for birth.

Third Trimester, Week 32 Gestational Age (Week 30 Fetal Development)

The layer of lanugo – the soft, downy hair – that covered your baby’s skin for the past several months begins to fall off now. She has toenails now and starts to practice breathing. She weighs about three and ¾ pounds.

Third Trimester, Week 32 Gestational Age (Week 30 Fetal Development)

The baby is growing and putting on weight, getting ready to be born. He has both toenails and fingernails now. His lungs continue to mature, although they need a few more weeks in your uterus to be fully ready for life outside. His bones are completely formed, but they are still soft. He stands almost 17 inches tall now.

Third Trimester, Week 33 Gestational Age (Week 31 Fetal Development)

Baby’s pupils in her eyes can now change size in reaction to light. She can also distinguish light from dark. Her bones have started to harden, but her skull bones are still soft and flexible.

Third Trimester, Week 34 Gestational Age (Week 32 Fetal Development)

Her lungs and central nervous system keep developing as your baby grows and puts on more weight. Her skin is soft and smooth. Her fingernails have reached the tips of her fingers. She stands about 18 inches tall and weighs more than four and ½ pounds.

Third Trimester, Week 35 Gestational Age (Week 33 Fetal Development)

Your baby’s arms and legs start to look chubby, thanks to all the weight he has gained.

Third Trimester, Week 36 Gestational Age (Week 34 Fetal Development)

Things are pretty crowded for your baby now that he takes up almost all the space inside the amniotic sac. It is harder for him to punch you, but you will still feel him stretch, roll and wiggle inside you.

Third Trimester, Week 37 Gestational Age (Week 35 Fetal Development)

Your baby is now considered “early term” if she were to be born. Babies born now usually do well, but it is best for yours to stay inside for another few weeks. This gives her lungs and brain time to mature completely. Her head will turn down into your pelvis in preparation for delivery. If this does not happen over the next week or two, your doctor will talk with you about ways to deal with the issue.

Third Trimester, Week 38 Gestational Age (Week 36 Fetal Development)

If your baby were born now, he would be considered “full term.” This means he could make his debut any time now. His head and his abdomen are about the same circumference around. His fingernails are long enough that the nurses will probably trim them soon after he is born. As he gets bigger, you may notice changes in his movement. It is very crowded in your belly now. However, if you see your baby stops moving or has a significant reduction in his movements, you should contact the doctor immediately.

Your body is busy giving the baby antibodies to protect him against diseases. All the baby’s organs are developed now, although his lungs will keep maturing up until the day he is born. The baby measures between 19 and 21 inches tall and can weigh between six and ¾ pounds up to nine or ten pounds at delivery.

Third Trimester, Week 39 Gestational Age (Week 37 Fetal Development)

Your full term baby is ready for life outside of you. Fat continues to be deposited all over your baby’s body. The average weight of a newborn is about seven and ½ pounds, and their average height is about 20 inches. Newborns come in all sizes, though. Your doctor should be able to give you a good estimate of your baby’s size by measuring your belly during your prenatal visit.

Third Trimester, Week 40 Gestational Age (Week 38 Fetal Development)

This week is technically your baby’s due date. However, your due date was a calculation based on the date of your last period. It is entirely normal to go into labor before or after your due date. You probably feel like you have been pregnant forever. As long as your baby is healthy and your doctor says things are fine, try to stay comfortable and to walk as much as you can. This will help prepare your body for delivery. Remember - gravity will be your friend in the delivery room!

Third Trimester, Week 41 Gestational Age (Week 39 Fetal Development)

If you have passed your due date by a full week, you baby is considered “late term.” This is not a concern. Your doctor will continue monitoring you and your baby. He or she will check the status of your cervix to see if you have started to dilate in preparation for delivery. If you are still pregnant at 42 weeks, your baby is “post-term.” At this point, the obstetrician may do more non-stress tests and may talk to you about inducing labor.

Read the other guides in our three-part series:

This concludes our series on what to expect during the three trimesters of your pregnancy. Very soon you will be ready for labor and delivery! If you have any questions or concerns during your third trimester of pregnancy, or you need to schedule a prenatal appointment, call our office at 913-948-9636.