At 27 weeks, you’re entering the final stretch of pregnancy. This week marks the very beginning of the third trimester, and your baby now weighs about 2¼ pounds (1 kg) and measures roughly 13¾ inches (35 cm) from head to heel. A lot is changing for both of you right now, from your baby’s rapidly maturing nervous system to a new set of physical symptoms you may not have experienced before.
Your Baby at 27 Weeks
Your baby’s nervous system is actively maturing this week. Brain connections are forming rapidly, and your baby is developing more defined sleep and wake cycles. You may notice a pattern to when they’re active and when they’re quiet, especially in the evening and at night.
The lungs are still developing and won’t be fully mature for several more weeks, but they’re making progress. The eyes can open and close now, and your baby is practicing breathing movements by inhaling and exhaling small amounts of amniotic fluid. At about the size of a head of cauliflower, your baby is gaining fat under the skin, which will help regulate body temperature after birth.
How Your Body Is Changing
The third trimester brings a new wave of physical changes, some familiar and some entirely new. Your uterus is now well above your belly button, and the growing pressure it puts on surrounding organs explains many of the symptoms that show up around this time.
Braxton Hicks contractions often become noticeable around now. These are mild, irregular tightening sensations in your abdomen that come and go without a pattern. They tend to show up in the afternoon or evening, after physical activity, or after sex. They typically last less than a minute and happen only once or twice an hour. Changing positions, like sitting down if you’ve been walking, usually makes them fade.
Shortness of breath is common as your baby pushes upward against your rib cage. You might notice it more when lying on your back. Heartburn and constipation can also pick up because pregnancy hormones slow your digestion while your uterus presses against your intestines. Backaches are another frequent complaint, caused by hormones loosening your pelvic connective tissue combined with stretched abdominal muscles that can no longer support your spine as well.
Some less expected symptoms can also appear. Heart palpitations, that fluttering or pounding feeling in your chest, happen because your growing uterus slows blood flow back to your heart. Spider veins (tiny red or purplish veins) may appear on your skin as your blood volume increases, and varicose veins can develop in your legs. Hemorrhoids, which are essentially varicose veins in the rectal area, are also common in the third trimester. Frequent urination ramps up again as the baby moves lower in your pelvis and presses on your bladder, and you may start leaking urine when you laugh, cough, or sneeze.
Prenatal Appointments and Screenings
If you haven’t already had your glucose screening test, it’s likely scheduled right around now. Most providers test for gestational diabetes between 24 and 28 weeks using a one-hour glucose challenge test. You’ll drink a sugary solution and have your blood drawn an hour later. If the results come back elevated, a longer follow-up test confirms or rules out gestational diabetes.
If your blood type is Rh-negative, you’ll receive an injection of Rh immunoglobulin (commonly known as RhoGAM) between 26 and 28 weeks. This prevents your immune system from producing antibodies that could attack your baby’s red blood cells if your baby is Rh-positive. It’s a routine shot, usually given in the arm or hip.
Your provider will also check your blood pressure and weight at each visit and ask about any new symptoms. These checks become more important as the third trimester progresses.
Nutrition in the Third Trimester
Your baby’s rapid growth means your nutritional needs are higher now. Iron is one of the most critical nutrients during pregnancy, with a recommended daily intake of 27 mg. Iron supports the increased blood volume your body is maintaining and helps deliver oxygen to your baby. Red meat, beans, spinach, and fortified cereals are good sources, and your prenatal vitamin likely covers a significant portion.
Calcium intake should be around 1,000 mg per day for adults 19 and older (1,300 mg for those under 19). Your baby is building bone, and if you’re not getting enough calcium from your diet, your body will pull it from your own bones.
Omega-3 fatty acids, particularly DHA, play a key role in your baby’s brain development during the third trimester. Expert guidelines recommend at least 250 mg per day of DHA and EPA combined, with an additional 100 to 200 mg of DHA on top of that during pregnancy. Eating 8 to 12 ounces of low-mercury seafood per week, like salmon, sardines, or shrimp, generally covers this. If you don’t eat fish regularly, a DHA supplement is a reasonable alternative. Intakes up to 1,000 mg per day of DHA have not raised safety concerns in pregnant women.
Starting Kick Counts
Now that you’re in the third trimester, tracking your baby’s movements becomes a useful daily habit. Pick a time when your baby is usually active (often in the evening), sit with your feet up or lie on your side, and count every kick, jab, poke, or roll until you reach 10 movements. Most babies hit 10 within about 30 minutes to two hours.
The specific number matters less than the pattern. Once you have a sense of what’s normal for your baby, a noticeable change, like taking much longer than usual to reach 10 movements or a significant drop in activity, is worth reporting to your provider.
If Your Baby Were Born Now
At 27 weeks, a baby born prematurely would need significant medical support but has a strong chance of survival. Data from neonatal units shows survival rates of 60 to 70 percent at 24 weeks and 80 to 90 percent at 28 weeks, placing 27 weeks solidly in between. Babies born at this stage typically require time in the NICU to support breathing, feeding, and temperature regulation, and outcomes have improved substantially over the past decade. The risk of long-term health complications drops with each additional week in the womb.
Preterm Labor Warning Signs
Knowing the difference between Braxton Hicks contractions and actual preterm labor is important at 27 weeks. Braxton Hicks are irregular, mild, and stop when you change activity. Real labor contractions become regular, progressively stronger, more frequent, and longer lasting. They don’t go away when you rest or shift positions.
Contact your provider right away if you experience contractions more than four times in an hour, a persistent dull ache in your lower back, pressure in your pelvis that feels like the baby is pushing down, stomach cramps that feel like period pain, or any fluid or blood leaking from your vagina. Nausea, vomiting, diarrhea, sudden swelling of your hands or face, or vision changes like blurring or double vision also warrant an immediate call. Before 37 weeks, any of these symptoms should be evaluated quickly.