Everything You Need to Know About The Third Trimester of Pregnancy

Dates: The Beginning of Week 27 – The End of Week 40

You’ve been counting down the weeks for half a year now. Maybe the time has gone quickly for you, or maybe you feel like you’ve been pregnant forever. You may find yourself nesting hard or waking in the middle of the night fretting over whether you’re ready for this baby to arrive.

The third trimester can be difficult physically too, and you might be feeling the strain on your internal organs and musculoskeletal system. No matter how uncomfortable you feel, remember you’re almost there, and soon you’ll forget all this discomfort as you gaze at the newborn baby in your arms.

Third Trimester Baby Development

27 Weeks: Your baby now weighs about 1.9 pounds and looks similar to a newborn—only smaller and thinner. The ability to thrive outside the womb improves with each passing day, and statistics show there’s a 90 percent chance of survival at 27 weeks. Through a series of step-like leg motions similar to walking, your baby performs somersaults. Rapid Eye Movement indicates fetal dreaming, and during waking periods, the eyes blink. Your baby’s eyes can open, but they stay mostly closed, and sight, hearing, taste, and smell become more developed. You might feel hiccups in the third trimester as your baby practices breathing and activates the nerve that controls the diaphragm. Right now, you’ll probably see your OB-GYN as often as every two weeks.

28 Weeks: Your baby will use additional calcium as more cartilage converts to soft, pliable bone. Further ear development allows babies to distinguish low and high-pitch sounds, which they noticeably react to, and new research reveals babies may make their first silent cries in the womb to express displeasure at 28 weeks. All nerve connections from the ears to the brain are complete, as the brain’s surface wrinkles to hold more brain cells. You might feel Braxton Hicks “practice contractions” now as the body rehearses for the big day. Around this time, doctors may check to see if your baby is head down or feet down in the “breech” position. There is still plenty of time to shift, but babies who remain in the breech position may need to be delivered by cesarean.

29 Weeks: Your baby’s lungs are maturing to allow greater respiration, and the eyes demonstrate increased sensitivity, following light around the womb. The head is growing larger to accommodate the billions of developing neurons, and your baby’s brain is sophisticated enough to see, hear, remember, and learn! Your baby’s acrobatics indicate a growing effort to develop limb strength that will help position and maneuver them through the birth canal to the outside world. Those little flutter movements have turned into karate kicks and punches. You should feel at least ten movements every two hours. A kick count is optimally conducted at night, after dinner, while lying on your side. If you aren’t feeling as many kicks as you think you should, consult your doctor.

30 Weeks: At 30 weeks, bone marrow produces red blood cells, and your baby’s body absorbs and stores calcium, iron, phosphorus, and protein. The brain prepares to double in weight over the last 11 weeks of pregnancy, mostly due to the thickening of the myelin sheath surrounding the nerves, which helps to protect them so they can send and receive signals quickly. By the time your baby is born, the brain will be a quarter of its adult size, but it will have perhaps 100 billion neurons—the most it will ever have. Around 30 weeks, your baby’s lungs will start producing surfactant, a substance that helps to keep open the tiny air sacs in the lungs. An average baby at this stage weighs about 3 pounds and measures 17 inches from head to toe. Many moms may begin to feel breathless as the uterus expands and crowds out the diaphragm.

31 Weeks: A phase of rapid weight gain begins right about now for your baby. In the coming weeks, your baby will more than double their weight. The amount of amniotic fluid decreases to about a pint and a half, which is why those kicks and punches feel so sharp these days. The digestive tracts are almost mature, with kidney and urinary health gauged by checking amniotic fluid levels if necessary. The hair on your baby’s head grows longer, and the baby can’t move and kick quite as forcefully as space in utero decreases.

32 Weeks: Development begins on the alveoli, the tiny sacs that allow the transfer of oxygen and carbon dioxide between the lungs and bloodstream. This development will continue until your child is roughly eight years old. Babies tend to be very busy sucking their thumbs, swallowing, kicking, and breathing to hone their survival skills. Your baby gained another pound of fat over the last two weeks, grew almost two inches, and is about the size of a half-gallon of milk now.

33 Weeks: There is less room in the womb now, with sonograms revealing all sorts of comical positions: from legs-crossed yoga poses to bent knees with the chin resting on the fist in “the thinker” pose. Your baby’s immune system is borrowing antibodies from your body, and bones are hardening. The eyes remain open during wakeful periods. High-risk pregnancies may have a biophysical profile done around this time to check for fetal movement, breathing, muscle tone, and amniotic fluids. A non-stress test measures how the baby’s heart rate changes during movements or contractions. These same tests may also be ordered when mothers go beyond their due dates.

34 Weeks: Your baby’s internal organs are fully formed, with the exception of the lungs. The skin is still red, the toenails are growing, and the fingernails have reached your baby’s fingertips. Many babies start turning, flipping, and transitioning to birth position. You may notice your bump shift a bit lower if your baby has changed positions recently. The descent makes breathing easier but places greater pressure on the bladder and pelvis, meaning more trips to the bathroom and round ligament pain. Belly measurements at this point range from 32 to 36 inches from the top of the uterus to the pubic bone. Measurements out of the normal range may indicate bigger or smaller babies, as well as breech or sideways positioning. Abnormal fundal height may prompt your doctor to request an extra ultrasound to be sure they’ve calculated your due date correctly and your baby is healthy and growing.

35 Weeks: Your baby now has a firm hand grasp, and fat stores help with temperature regulation, though this is still developing. Your baby’s reflexes are smoother and more coordinated. Between 35 and 37 weeks, doctors routinely take a culture to test for the presence of Group B Streptococcus bacteria, for which 20–25% of women test positive. GBS poses no threat to moms but is fatal for 1% of newborns. If GBS is detected, you begin antibiotics when labor starts in order to reduce the risk of infection. The clock starts ticking now for mothers of twins, as most twin births take place between 35 and 37 weeks.

36 Weeks: At this stage, most babies weigh about 6 pounds and measure over 20 inches. You may have started waddling now, as you feel the extra weight you’ve gained over the course of your pregnancy. Doctors may attempt to shift a breech position baby ahead of time by a low-risk method of pressing gently on your abdomen, which works about 50 percent of the time. You will start visiting the OB-GYN on a weekly basis now. These visits may entail a pelvic exam to check for cervix opening and thinning—two signs your body is preparing for labor. Once you’ve started that process, it could be hours—or weeks still—before the baby is born. 

37 Weeks: Your baby’s skin is turning pink and becoming less wrinkly. After your baby’s rapid growth spurt, you can expect their weight gain to slow a bit now, putting on half a pound or so each week. Your baby’s coordination is so fine-tuned, they can grasp with their fingers. Movement is generally slow since there’s so little room, but you may feel stretching, rolling, pivoting, and wiggling.

38 Weeks: Most of the lanugo (a thin layer of hair on your baby) and vernix (a waxy, white coating) have been shed in preparation for birth, though a small amount will still be present when your baby is born. Some babies have up to an inch of hair already. Boys’ testicles usually drop down into their scrotums, and the labia are completely developed in girls. Your baby’s lungs are producing more and more surfactant, preventing the air sacs from sticking to each other when your baby is taking breaths. Fat continues to build beneath the skin, and the average baby weighs 6.8 pounds.  

39 Weeks: Congratulations! You are now considered “full term,” meaning that your little one is likely to be perfectly healthy if you deliver now. Ultrasounds can show amazing details like eyelashes, and your baby’s brain continues to grow at an astonishing rate. Your baby has developed considerable strength in the arms and legs and will be closer to the average newborn baby size of about 7.6 pounds and 20.2 inches in length.

40 Weeks: Right now, your baby is about the size of a watermelon or pumpkin, and hair and nails are continuing to grow. Only 5% of babies arrive on their precise due dates, so be prepared to wait if you haven’t delivered already. At this point, it’s a good idea to talk to your health care provider about when you would want to formulate a backup labor plan that may include induction or a cesarean.  Your doctor will continue to monitor you and your baby to make sure you’re both healthy.

Your Physical Changes in the Third Trimester

With the finish line now in sight, excitement and anxiety can peak. Some mothers feel apprehensive about the changes ahead, while others can’t wait to meet their new little person. In terms of physical changes, you may notice

• Backaches and pelvic pain: The joints loosen in preparation for labor. The growing weight of the uterus and baby adds to the pressure on your spine, muscles, blood vessels, and nerves.
• Braxton Hicks contractions: You may experience these irregular, pre-labor contractions that are your body’s way of “practicing” for labor. While these contractions can be uncomfortable, you probably won’t notice any regularity in their timing.
• Changes in vaginal discharge: If watery fluid seeps out, you could be losing amniotic fluid and going into labor! If you see blood-tinged discharge (called “bloody show”), you may have passed the mucus plug—a sign that labor is very near.
• Clumsiness: As your body changes, you might find yourself feeling clumsier, and your ligaments will be looser, making it easier to fall or twist an ankle. Be sure to take extra caution as you move around.
• Constipation: Pregnancy hormones slow digestion, which sometimes causes constipation.
• Cramping: Early labor is characterized by 30 to 45-second cramps, with five to 30 minutes of rest in between. They begin mild, like period cramps, and gradually increase in frequency and intensity.
• Fatigue: It takes a lot of energy to fuel your baby’s development and move the extra weight around, so you’ll probably be extra tired during the third trimester.
• Frequent, urgent urination: The baby’s size puts pressure on the bladder, preventing it from filling up before needing to be emptied. Lying on your left side will increase kidney efficiency.
• Heartburn: Eating small meals throughout the day is preferable to eating three larger meals. Your baby compresses your digestive organs, causing heartburn and gas.
• Hemorrhoids and varicose veins: The growing uterus puts pressure on your veins and rectum, causing new bulges. The good news is that they’ll disappear postpartum.
• Insomnia: Three in four pregnant women experience insomnia in their third trimester. Hormonal changes, late-night bathroom trips, and anxiety about the uncertainty of labor can all cause sleepless nights. With hormones playing funny tricks on the body, you may also start having strange dreams.
• Itchy skin: Since your skin stretches to accommodate your growing baby, many women experience itchy skin in the third trimester. About 1 in 150 women develop an itchy, bumpy rash across the stomach and extremities. Try some lotion or belly balm for relief from the itching.
• Kicks in the ribs: The uterus reaches up to the bottom of the rib cage, and many babies flip upside down in preparation for birth.
• Lightening: Some women experience the feeling of the baby moving down to the pelvis, which may make your bump look and possibly feel lighter. Even if you don’t feel anything, you may be able to eat more food and breathe easier.
• Swollen feet and legs: Increased blood flow and pressure from your uterus can cause swelling in the lower extremities. Compression stockings or elevating the feet can help, but if you notice other signs of preeclampsia, be sure to seek medical attention immediately.
• Swollen, leaky breasts: Some women experience leaking colostrum, the yellowish substance that will be your baby’s first food.

Third Trimester To-Do List

1. Take any childbirth and breastfeeding classes you signed up for.
2. Start or continue preparing older children for their new sibling with books and discussions. Some parents find it helpful to give older children their own doll so they can practice being a big brother or sister.
3. Interview prospective pediatricians and decide where your child will go.
4. Wash all baby linens, cloth diapers, baby slings, and clothing.
5. If you’re delivering at a hospital, preregister so they have all your information ahead of time.
6. Stock the pantry with grab-and-go snacks and the freezer with prepared meals.
7. Arrange for postpartum help, whether you’re going to hire a doula or baby nurse or take up any friends and family on offers to help.
8. Properly install your baby’s car seat. You’ll need to have a car seat that meets current safety standards with you at your hospital or birthing center.
9. Look over your breast pump manual. Sterilize all parts and bottles.
10. Make sure you have nursing bras and comfortable clothing ready for your recovery.
11. Assemble playpens, strollers, and baby swings.
12. Spend quality time with your partner, friends, and older children.
13. Review your birth plan and establish a game plan for what you’ll do when contractions begin.
14. Pack a bag for the hospital. (Check out our lists of what to bring and what to leave at home!)

What Kindred Bravely Moms Remember About the Third Trimester

Every woman will experience the third trimester differently, but hearing from others who have gone through what you're about to experience can be helpful when you're feeling confused or overwhelmed. Talk to the women in your life who have been there, or reach out to the amazing moms in our Facebook group, KindredMamas. Knowing that you have a supportive community can make all the difference in the world.

To get you started, here are some third-trimester memories that KB Moms have shared. They reflect the variety of ways the third trimester impacted them both physically and emotionally:

• “I loved utilizing the website Spinning Babies in my third trimester to ease back pain. I also slept with a peanut ball between my legs to help with comfort at night. My husband would pick up my big belly by standing behind me, clasping his hands under my belly, and lifting up; this helped take the weight and pressure off so much! Walking daily kept me energized and kept my toddlers active. I did anything to take my mind off the approaching due date—swimming, trips to the zoo, hiking, nature parks, playing at the park with my older kids—that was my focus. I prepared for my breastfeeding journey by reading. One of my favorite books was The Womanly Art of Breastfeeding.” – Shantel

• “The third trimester was definitely not my favorite. I was back to being tired most of the time, and moving around was difficult—especially getting in and out of bed! My feet were so swollen—I had to buy special shoes because none of mine fit. Every time I got in the car to drive anywhere, my son decided he wanted to dig his elbow and foot into my rib cage. It wasn’t all bad, though. The baby got the hiccups a lot. You’d think that would bother me, but I actually loved it. I realized that I slept better if I worked out, so I made sure to exercise every day. The best part about the third trimester was being so close to meeting my little man. He arrived a couple days early—and for that, I’m very thankful!” – Stephanie
  
  
• “In my most recent pregnancy, the third trimester was the first time I finally had some energy. I kept waiting for the energy burst that usually comes during the second trimester, and finally, it arrived a few weeks into the third... just in time for my belly to be HUGE. The nesting instincts were out of control. The desire to eat lots and lots of ice cream was real! And, since this was the third baby, I literally felt like she was going to fall out of me at any given moment.” – Lauren

Congratulations on making it to your third trimester! You are an amazing mama already, and the journey is just beginning. As much as possible, try to enjoy these last weeks of pregnancy, and know that you have so much to look forward to!