31 Weeks Pregnant: Baby Is Practicing Breathing

At 31 weeks pregnant, you’re in the final stretch of your third trimester with only about 9 weeks to go until your due date. Your baby is continuing to grow and gain weight rapidly, and your body is working overtime to support this incredible development. This week marks a significant milestone as your baby’s organ systems become increasingly sophisticated and survival rates outside the womb continue to improve. Many women at this stage start experiencing more noticeable discomfort as their pregnancy weight increases, but understanding what’s happening with both you and your baby can help you navigate this exciting time with confidence.

Baby Development at 31 Weeks

Your baby is about the size of a coconut this week—roughly 16-17 inches long and weighing approximately 3.5-4 pounds. That’s nearly double what your baby weighed just 6 weeks ago, and this rapid growth will continue through delivery.

Your baby’s brain is developing at an astonishing rate right now. The brain’s surface area is increasing dramatically as more folds and grooves develop, which helps support cognitive development and memory formation. Your baby’s bone structure is continuing to harden, though their skull remains pliable to allow for passage through the birth canal. The soft spots (fontanels) on your baby’s head will remain flexible even after birth to facilitate growth.

At 31 weeks, your baby’s respiratory system is nearly mature. The tiny air sacs called alveoli are now producing surfactant—a crucial substance that helps the lungs inflate and function properly after birth. This is why babies born at 31 weeks have significantly better survival rates and fewer complications than earlier premature births.

Your baby is now able to regulate their own temperature better and has developed sufficient fat stores under their skin to help maintain body temperature after birth. Their immune system is also becoming more developed, particularly through the transfer of maternal antibodies through the placenta. The eyes continue to respond to light, and your baby’s hearing is fully developed. Many babies at this stage are sleeping 20-25 hours per day while in utero, cycling through quiet and active sleep phases.

Your Body This Week

At 31 weeks, you’ve likely gained between 20-25 pounds, though the exact amount varies based on your pre-pregnancy weight and other factors. Your uterus is about 4 inches above your belly button and continues to expand. Many women describe their belly as feeling tight and heavy at this stage, and you may notice that your center of gravity has shifted significantly, which can affect your balance and gait.

Your blood volume has increased by about 50% compared to pre-pregnancy levels, which means your heart is working harder to pump blood throughout your body and to the placenta. This increased circulation can cause varicose veins, spider veins, and hemorrhoids—all temporary conditions that often improve after delivery.

By this point in pregnancy, you’re likely experiencing some degree of back pain or pelvic discomfort. The weight of your growing belly pulls your center of gravity forward, placing extra strain on your lower back. Additionally, the hormone relaxin continues to loosen the ligaments in your pelvis in preparation for birth. Many women find that prenatal massage, pelvic floor physical therapy, or a maternity support belt can provide significant relief.

Your breathing may feel slightly more difficult at this stage, a condition called dyspnea of pregnancy. This occurs because your growing uterus pushes up on your diaphragm, giving your lungs less room to expand fully. This is completely normal and should improve somewhat after 36 weeks when your baby “drops” lower into your pelvis.

Common Symptoms at 31 Weeks

Braxton-Hicks Contractions: You may notice your belly tightening occasionally, usually lasting 30 seconds to 2 minutes. These practice contractions become increasingly common as you approach your due date. You can distinguish them from labor contractions because they’re typically painless, don’t occur at regular intervals, and go away with position changes, hydration, or walking.

Swelling (Edema): Many women experience increased swelling in their feet, ankles, hands, and face. While some swelling is normal, sudden swelling of the face or hands can be a sign of preeclampsia and should be reported to your healthcare provider immediately. Mild swelling often improves with elevation, staying hydrated, and wearing compression socks.

Fatigue: Many women feel more tired than ever at 31 weeks. Your body is investing enormous amounts of energy into growing your baby and preparing for labor. This is not laziness—it’s a biological signal that your body needs rest.

Sleep Difficulties: The combination of physical discomfort, frequent urination, vivid dreams, and anxiety about labor can make sleeping through the night increasingly challenging. Prenatal pillows can provide support for your belly, back, and knees. Sleeping on your left side is particularly beneficial as it optimizes blood flow to the placenta.

Digestive Issues: Constipation and hemorrhoids are increasingly common as your growing uterus puts pressure on your digestive system. Staying well-hydrated, eating fiber-rich foods, and staying active can help.

Leg Cramps: Changes in calcium and magnesium metabolism, and pressure on your nerves can cause painful leg cramps, particularly at night. Staying hydrated, stretching your calves regularly, and applying heat can help prevent cramps.

What to Do This Week

Schedule Your Next Appointments: At 31 weeks, you should be having appointments every 2 weeks, which will increase to weekly visits starting at 36 weeks. These appointments allow your provider to monitor your baby’s position, check your blood pressure and urine, and assess for any signs of complications.

Start Planning Your Birth: If you haven’t already created a birth plan, this is an excellent time to do so. Discuss your preferences regarding pain management, delivery position, immediate postpartum care, and feeding preferences with your healthcare provider. Keep in mind that labor often has a way of changing our plans, and flexibility will serve you well.

Prepare Your Hospital Bag: This is a good time to start thinking about what you’ll want at the hospital or birth center. You’ll want items for labor (comfort items, music, massage tools), items for your baby (receiving blankets, onesies), and items for postpartum recovery (comfortable going-home outfits, toiletries, cozy socks).

Stay Active: Continue with pregnancy-safe exercises like walking, swimming, prenatal yoga, or modified strength training. Physical activity helps manage weight gain, improves sleep, reduces back pain, and can facilitate an easier labor.

Practice Relaxation Techniques: Start exploring relaxation methods you might use during labor—whether that’s breathing exercises, visualization, affirmations, or meditation. Practicing these techniques now makes them easier to access when you’re in labor.

Nutrition Spotlight: Iron and Protein

At 31 weeks, your iron needs are particularly important as you prepare for potential blood loss during delivery. The recommended daily allowance for iron in pregnancy is 27 mg per day. Iron helps create hemoglobin, which carries oxygen throughout your body and your baby’s body. Without adequate iron, you’re at increased risk for anemia.

Iron comes in two forms: heme iron (from animal products, absorbed at 15-35% efficiency) and non-heme iron (from plant-based sources, absorbed at 2-20% efficiency). Heme iron sources include: lean red meat, poultry, fish, and shellfish. Non-heme iron sources include: legumes, fortified cereals and grains, dark leafy greens, dried fruit, and seeds.

To maximize iron absorption, consume iron-rich foods with vitamin C sources (citrus, berries, tomatoes, bell peppers). Avoid consuming tea, coffee, and calcium supplements within 2 hours of iron-rich meals. Protein is equally crucial at this stage—aim for 70-100 grams daily from sources like Greek yogurt, eggs, fish, chicken, beans, lentils, nuts, and seeds. Review our guide on foods to avoid during pregnancy for safety reminders.

When to Call Your Doctor

Contact your healthcare provider immediately if you experience:

• Severe or sudden swelling in your face, hands, or feet, particularly with headache or vision changes
• Sudden or severe headache, especially with vision changes or upper abdominal pain
• Vaginal bleeding that is more than light spotting
• Severe cramping or abdominal pain that doesn’t improve with rest
• Gushing or constant leaking of fluid from your vagina
• Significantly decreased fetal movement
• Fever above 100.4°F (38°C)
• Severe nausea and vomiting preventing you from keeping down food or fluids
• Painful urination with urgency and frequency
• Chest pain, difficulty breathing, or feeling faint

Frequently Asked Questions at 31 Weeks

Is it normal to feel more fatigued at 31 weeks than in earlier pregnancy?

Yes, absolutely. By the third trimester, your body is working incredibly hard to support your growing baby, manage the physical burden of pregnancy weight, and prepare for labor. Fatigue is your body’s way of signaling that it needs rest. If you’re experiencing extreme fatigue, discuss this with your healthcare provider to rule out conditions like anemia or thyroid issues.

What’s the difference between Braxton-Hicks contractions and real labor contractions?

Braxton-Hicks contractions are typically irregular, don’t increase in intensity, don’t get closer together, and may be relieved by rest, hydration, or position changes. They feel like tightening across your abdomen but aren’t painful. Real labor contractions occur at regular intervals, progressively increase in intensity and duration, continue regardless of what you’re doing, and are typically accompanied by cervical changes.

Should I be concerned about swelling at 31 weeks?

Mild swelling of the feet, ankles, and hands is very common in the third trimester and usually doesn’t indicate a problem. However, sudden or severe swelling, particularly of the face or hands, or swelling accompanied by headache, vision changes, or upper abdominal pain, could indicate preeclampsia and requires immediate medical evaluation.

Can I still exercise at 31 weeks?

Most women can safely continue exercise at 31 weeks. Walking, swimming, prenatal yoga, stationary cycling, and modified strength training are generally safe and beneficial. Avoid contact sports, high-impact activities, and anything that increases your risk of falling. Always listen to your body and stop any activity that causes pain, shortness of breath, or dizziness.