Your Third Trimester

57441459_22.jpgWelcome to your third and final trimester! At 28 weeks, you are officially on the downhill slope, you can see the light at the end of the tunnel, you're on the homestretch... and yet, clichéd expressions aside, there are so. many. long. days. ahead.

The third trimester, while exiting, often brings with it added aches and pains, less sleep, frequent attention from strangers (there's no hiding your pregnancy now!), and lots more prenatal appointments. On the flip side, the third trimester also brings fun preparations for baby's arrival, childbirth classes, feeling baby move all the time, and for many, extra attention, support, and help. Like I always say, everyone's experience during pregnancy differs, so try not to get hung up on comparison.

Like our "Your First Trimester" and "Your Second Trimester" posts, we want to make sure you have the most useful and helpful basic information about your third trimester in a quick and easy-to-read post. So, here goes. 

How long is the third trimester?

The third trimester is unique in that how long it lasts can vary between 12 to 15 weeks (and beyond, for some), or less than 12 weeks if you give birth prematurely (before 39 weeks). The third trimester begins at 28 weeks. A full term pregnancy is between 39 and 41 weeks. "Late term" is the 41-42 weeks, and "post term" is after 42 weeks.  

What happens to baby in the third trimester?

Your baby is growing, developing, and moving in the third trimester! In these last few months, your baby really begins to add on the fat they need to survive and be healthy outside of your body. Most of the systems are well developed by the third trimester, except for baby's lungs, which are still maturing. This is one of the most important reasons why every week of pregnancy counts! Lung maturation happens up to the moment of birth. If your baby were to be born early in the third trimester, they would likely need interventions to support healthy lung functioning. 

During the third trimester, your baby's hearing is fully developed and can respond to sounds. Toward the end of the trimester, your baby's reflexes are in full swing and coordinated -- they can close eyes and blink, grasp with fingers, and respond to sound, light, and touch. By the end of this trimester, baby will have eyelashes and eyebrows and may either have a full head of hair or barely any. 

Movements in the third trimester can cause feelings of awe, discomfort, and hilarity. As your baby grows, there's less room to move around, but that doesn't stop them from trying! You'll likely experience the odd sensation of baby rolling around, stretching arms and legs, and even "bouncing" in your abdomen. You're also now able to feel baby's hiccups which can feel fun or annoying, especially if it's frequent. 

In the middle to late third trimester, your baby will begin to get in position for birth. Ideally, this will be head down, chin tucked, and facing your back or side, but babies don't always get that memo. Your care provider will help you determine your baby's position, and if your baby is breech (head up), will discuss options trying to turn baby head down.   

By the end of the third trimester, baby will be anywhere from 6-9 pounds on average if you give birth at full term. Of course, some babies are smaller and some larger even if they're born at the same time. Babies born earlier can of course weigh much less. If your baby is born at or after 28 weeks, there is a good chance of survival due to the many advances and knowledge we have in premature baby care. 

What happens to me in the third trimester?

Oh third trimester, how I love/loathe thee. For most people, the third trimester includes a lot of physical symptoms, many of which are not exactly "fun" and some of which are downright debilitating. Because this trimester is when your baby is at their biggest in size, you are also at your "most" for experiencing symptoms. Physically, your body is going through tremendous change to accommodate baby's growth and weight. Additionally, as you near the end of the trimester, you experience a shift in hormones as your body prepares for birth. Estrogen, for example, is at its peak in the third trimester. You may experience an increase in mood swings during the third trimester due to fluctuating hormones. And for some in their third trimester, nausea may still be a thing. For others, nausea that went away may come back. And for others, nausea may finally go away.  

You may also experience any of the following in the third trimester: 

  • Shortness of breath
  • Increased tiredness or fatigue
  • Backache
  • Heartburn or increased heartburn
  • Leg cramps and/or numbness in legs and feet
  • Hemorrhoids
  • Spider or varicose veins
  • Stuffy nose/congestion
  • Difficulty finding comfort while sleeping 
  • Nausea
  • Dizziness
  • Stretch marks
  • Frequent urination
  • Heightened sense of smell and taste, along with aversions to food and scents
  • Mild swelling in feet and ankles
  • Round ligament pain (sharp pulling/pain or dull ache in lower abdomen, usually to one side, upon changing positions)
  • Mood and emotional changes
  • Reduced or high sex interest -- both are considered "normal"
  • Constipation or increased constipation
  • Physical bodily changes, including enlarged breasts and changes to waistline and abdomen
  • Regular or increased vaginal discharge
  • Skin changes, including itchiness and pigment changes
  • Braxton Hicks contractions, or an increase in 
  • Burst(s) of energy, often referred to as "nesting"
  • Increased anxiety about birth or parenting or both 

Will maternity clothes still fit in the third trimester?

There comes a time in most peoples' pregnancy when no shirt, no matter how "maternity" does not cover the underside of your belly. Your maternity clothes, in general, should last you until the end of your pregnancy, but it's not uncommon to experience a tighter fit with a little belly popping here and there. You will also likely experience an increase in breast size in the third trimester. Find a bra with good stretch and good support. 

How often will I feel baby move in the third trimester?

During the third trimester, you will start to notice that baby has regular sleep and awake cycles. You'll notice more activity when baby is awake, of course. In general, baby should be moving frequently throughout the day. In the third trimester, it's helpful and important to do "kick counts," which is a monitoring of your baby's movements during the same time every day. According to Count the Kicks, the first time your record your baby's movements, you should time how long it takes to feel 10 movements. It could be as little as 30 minutes to up to two hours. You will likely see a pattern that's normal for your baby if you do kick counts around the same time each day for several days throughout the third trimester. Learn more about counting movements at Count the Kicks.

What happens during prenatal care in the third trimester?

During the third trimester, from weeks 28 to 36, you'll see your OB or midwife once every two weeks. After 36 weeks, your visits will be weekly until labor. At each appointment, you'll have the continued routine checks of weight, blood pressure, and urine. Your care provider also will listen to your baby's heartbeat, feel your abdomen, and measure your fundal height (the area from your pubic bone to the top of your uterus), which generally corresponds to baby's size and growth. Toward the end of the third trimester, your provider also will check to see if baby is head down, which can usually be determined by feeling your abdomen. 

Around weeks 35-37, your OB or midwife will perform a Group B Strep test to determine if you are positive for the Group B Strep bacteria. This is done by swabbing the bacteria in your vagina. If you are positive (about 25% of people will have the bacteria), you will receive antibiotics during labor so as to prevent passing the bacteria to baby, which can be harmful. 

During the third trimester, continue to talk often to your doctor or midwife about birth. Be sure to talk about your choices and preferences in birth, asking questions as often as possible. How you're cared for during labor and birth can affect you and your baby for the rest of your lives. Learn more about how to "spot the best care."


What symptoms should I worry about in the third trimester?

Signs that could indicate a complication and require medical attention during the third trimester include:

  • Bleeding
  • Leak or gush of fluid prior to full term, 39 weeks
  • Severe abdominal pain
  • Abdominal cramping
  • Fever and/or chills
  • Painful urination
  • Excessive thirst
  • Swelling or puffiness in hands and/or face
  • Vision changes
  • Excessive nausea and vomiting 
  • Severe headache(s)
  • Leg or calf pain and/or swelling in one leg
  • Constant or frequent and intense lower back pain
  • Regular or frequent tightening of abdomen with or without low backache (before full term, 39 weeks)

If you experience any of the above, call your care provider right away. 

Other resources for your third trimester

We've written other helpful resources on the second trimester to help answer some of the questions that pop up during this time. Check it out:

Enjoying Your Third Trimester

Third Trimester Checklist

Heading Into Summer... In Your Third Trimester

Best Exercise for Your Third Trimester

Swelling in Your Third Trimester

Top Nutrients You Need in Pregnancy by Trimester

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