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Pregnancy

31 Weeks Pregnant

At 31 weeks pregnant, your baby is the size of a coconut. Learn about rapid brain growth, Braxton Hicks contractions, shortness of breath, and third trimester tips.

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Reviewed by: Whispie Editorial Team Evidence-Based Parenting Research

Published:

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This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.

Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or ACOG.

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Quick answer: Week 31 sits squarely in the third trimester. Most of your baby's organs and systems are already formed — the next several weeks are about maturation, weight gain, and fine-tuning of the brain, lungs, and immune system. For you, the focus shifts toward managing physical discomfort, watching for warning signs, and starting.

At a Glance

  • Trimester: Third trimester (weeks 28–40)
  • Weeks to go: About 9 weeks until your due date
  • Baby size: Coconut — roughly 41 cm (16 inches) head-to-heel, about 1.5 kg (3.3 lb)
  • Key milestone: Rapid brain development and fat accumulation; the baby is now beginning to look round and "ready"

Week 31 sits squarely in the third trimester. Most of your baby's organs and systems are already formed — the next several weeks are about maturation, weight gain, and fine-tuning of the brain, lungs, and immune system. For you, the focus shifts toward managing physical discomfort, watching for warning signs, and starting practical preparation for labor and birth.

Your Baby's Development This Week

At 31 weeks, your baby is in a phase of intense neurological growth. Billions of neural connections are forming, and the brain's surface is changing from smooth to grooved (the characteristic folds — sulci and gyri — that increase surface area for higher cognitive function). This process continues well after birth, but the architecture is being laid down now.

Your Body and Symptoms This Week

At 31 weeks, the physical demands of pregnancy are real. Your uterus has reached about 11 cm above your navel, your blood volume is about 50% higher than pre-pregnancy, and you are likely carrying 8–11 kg (18–24 lb) of extra weight. Common symptoms this week include:

Nutrition: What to Eat & Avoid This Week

In the third trimester your calorie needs increase by about 450 kcal per day above your pre-pregnancy needs. But quality matters far more than quantity — the baby is laying down fat, brain tissue, and bone now.

Prioritize:

Avoid: Raw or undercooked fish, meat, and eggs; unpasteurized dairy; high-mercury fish (swordfish, king mackerel, tilefish, shark); deli meats unless heated until steaming; alcohol entirely; caffeine above 200 mg/day; herbal teas not confirmed safe in pregnancy.

Movement & Exercise

ACOG recommends at least 150 minutes per week of moderate-intensity activity throughout pregnancy unless your provider has restricted activity. At 31 weeks, exercise improves sleep, supports stamina for labor, reduces back pain, and can lower the risk of gestational diabetes complications.

Good choices this week: Walking, prenatal yoga, swimming or water aerobics, stationary cycling, prenatal Pilates, and pelvic floor exercises (Kegels). Squats and pelvic tilts help prepare the pelvis for labor.

Avoid: Contact sports, activities with fall risk (skiing, horseback riding), scuba diving, hot yoga or saunas, exercise lying flat on your back for extended periods, and any activity requiring sharp twists or jumps. Stop and call your provider for chest pain, severe shortness of breath, dizziness, vaginal bleeding, fluid leakage, regular painful contractions, or decreased fetal movement after exercise.

Mental & Emotional Wellbeing

As the due date approaches, it is normal to feel a mix of excitement, anxiety, impatience, and even ambivalence. Sleep disruption amplifies emotional swings. Up to 1 in 7 pregnant women experiences depression or anxiety — these are medical conditions, not failures of character.

Helpful practices:

If sadness, hopelessness, racing thoughts, or persistent anxiety interfere with daily functioning, contact your provider. Treatment in pregnancy is safe and effective; untreated depression carries its own risks for both parent and baby.

Common Concerns & When to Call Your Doctor

Most third-trimester symptoms are normal. The following require same-day medical attention:

These can indicate preterm labor, preeclampsia, infection, or placental problems — all of which benefit from early evaluation.

Tests & Appointments This Week

Between 28 and 36 weeks, prenatal visits typically shift to every 2 weeks. At your week 31 (or 30 or 32) visit, expect:

GBS (Group B Strep) testing is done later, around 36–37 weeks. The glucose tolerance test for gestational diabetes is usually done between 24 and 28 weeks, so it should already be complete.

Tips for Week 31

  1. Start daily kick counts. Pick a consistent time of day (often after a meal). Count to 10 movements and note how long it took. Trends matter more than a single count.
  2. Sleep on your side with support. A pillow between the knees, behind the back, and under the belly transforms comfort.
  3. Begin your hospital bag list. You do not need to pack it yet — just write the list.
  4. Sign up for a childbirth class. Most run 4–6 weeks; starting now means finishing well before 40 weeks.
  5. Practice pelvic floor exercises daily. 3 sets of 10 Kegels reduces incontinence and supports recovery.

Preparing for What's Next

The next 4–6 weeks are a sweet spot for practical preparation. You still have energy and mobility, but the third-trimester reality of an impending baby is concrete. Consider:

Frequently Asked Questions

Is it normal to feel breathless at 31 weeks pregnant?

Yes. By 31 weeks your uterus has risen about 4 inches above your navel and is pressing on the diaphragm, which reduces lung capacity. Shortness of breath after climbing stairs or even speaking long sentences is very common. It usually improves around 36 weeks when the baby "drops" into the pelvis. Sit upright, sleep propped on pillows, and slow your pace. Call your provider if breathlessness comes on suddenly, is severe at rest, or is paired with chest pain or a fast heartbeat.

How many times should I feel the baby move at 31 weeks?

After 28 weeks, ACOG recommends doing daily kick counts. A common method is to count until you feel 10 distinct movements (kicks, rolls, jabs) — this should happen within 2 hours, and usually within 30 minutes when the baby is active. Movements should not decrease as you approach term, although the type of movement changes from sharp kicks to rolls and stretches as space tightens. Call your provider the same day if you notice a clear drop in movement.

Are Braxton Hicks contractions normal at 31 weeks?

Yes, Braxton Hicks (practice contractions) are common in the third trimester. They feel like the whole belly tightening, are irregular, do not get stronger or closer together, and usually ease when you change position, drink water, or rest. Call your provider if contractions become regular (e.g., 4 in 20 minutes), painful, or are paired with lower back pain, pelvic pressure, fluid leakage, or bleeding — these can be signs of preterm labor.

What is the baby's size at 31 weeks?

At 31 weeks, your baby is roughly the size of a coconut — about 41 cm (16 inches) from head to heel and weighing around 1.5 kg (3.3 lb). Most of the major organs are formed; the next 6–9 weeks are mainly about gaining fat, fine-tuning the brain and lungs, and practicing breathing and swallowing movements.

Why am I so tired again at 31 weeks?

Third trimester fatigue is real and has several causes: poor sleep from frequent urination and discomfort, a higher metabolic load (you are growing a 1.5 kg baby plus extra blood volume), iron levels dropping, and the physical work of carrying extra weight. Rest when you can, prioritize iron-rich foods, and ask your provider to check your hemoglobin if fatigue feels extreme.

Can I still sleep on my back at 31 weeks pregnant?

It is best to sleep on your side from the third trimester onward — left side is often recommended because it improves blood flow to the placenta, but either side is acceptable. Lying flat on your back can compress the vena cava (a major vein) and lead to dizziness or reduced blood flow to the baby. If you wake up on your back, do not panic — just roll to your side. A wedge pillow or pillow between the knees helps.

When should I worry about swelling at 31 weeks?

Mild swelling of the feet and ankles (edema) is normal in the third trimester from increased blood volume and pressure on pelvic veins. Worrying signs include sudden swelling of the face or hands, swelling in only one leg (possible blood clot), severe headache, vision changes (spots, blurriness), or upper-right belly pain — these can suggest preeclampsia and need same-day evaluation.

Should I be doing anything to prepare for labor at 31 weeks?

Yes — now is a great time to start hospital bag planning, finalize your birth preferences, sign up for a childbirth class if you have not already, tour the birth facility, and confirm pediatrician choice. You do not need to pack the bag yet, but a list helps. Practice pelvic floor and breathing exercises, and learn the difference between Braxton Hicks and true labor signs.

Is heartburn worse at 31 weeks?

For many women, yes. The growing uterus pushes the stomach upward and pregnancy hormones relax the valve between the stomach and esophagus, so acid backs up more easily. Eat smaller meals, avoid lying down for 2–3 hours after eating, sleep with your upper body slightly elevated, and skip trigger foods (spicy, fried, citrus, caffeine). Most antacids containing calcium carbonate are considered safe — confirm with your provider.

What tests happen around 31 weeks?

Between 28 and 32 weeks, prenatal visits typically shift to every 2 weeks. You may have an additional growth ultrasound if you have risk factors, a repeat antibody screen if you are Rh-negative (with a RhoGAM injection around 28 weeks), and ongoing blood pressure and urine checks for preeclampsia. GBS testing happens later, around 36–37 weeks.

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