Week 31 of Pregnancy: Your Baby Is the Size of a Coconut

TL;DR

• Your baby is about 41.1 cm long — roughly the size of a coconut
• Your baby can now turn their head from side to side, responding to stimuli
• Sleep may feel nearly impossible between discomfort, bathroom trips, and restless legs
• Practice deep breathing exercises to prepare for labor

Your Baby This Week

Your baby is becoming more coordinated and responsive with each passing day. This week, they can turn their head from side to side — a sign that their neck muscles are strengthening and their neurological development is progressing nicely. They're responding to sounds, light, and even touch, turning toward familiar voices and away from bright lights.

At about 41.1 cm long and around 3.3 pounds, your baby is starting to look more and more like a newborn. Their skin is becoming less translucent as fat layers build up underneath, and their facial features are becoming more defined. Those tiny fingernails have grown to the tips of their fingers — and some babies even scratch themselves in the womb.

Your baby's five senses are all functioning now. They can taste the amniotic fluid (which changes flavor based on what you eat), hear your heartbeat and voice, see changes in light, feel the walls of the uterus around them, and respond to temperature changes. It's a rich sensory world in there.

Sleep cycles are becoming more established too. Your baby spends most of their time in REM sleep, which is essential for brain development. When they're awake, they're active — kicking, stretching, sucking their thumb, and practicing the movements they'll need after birth.

Your Body This Week

Getting comfortable enough to fall asleep might feel like solving a puzzle every night. Between the size of your belly, the ache in your back, the need to pee every two hours, and the restless legs that just won't quit, sleep is a real challenge. A pregnancy pillow between your knees and under your belly can help. Some people find that a warm (not hot) bath before bed relaxes muscles enough to drift off.

Braxton Hicks contractions may be more frequent now. These practice contractions usually feel like a tightening or hardening of your uterus that lasts 30 seconds to two minutes. They're irregular and shouldn't be painful. Dehydration can trigger them, so keep water nearby at all times.

You might be noticing more pressure in your pelvis and lower abdomen. This is your baby settling deeper, and while it's a good sign for birth preparation, it can make walking feel uncomfortable and increase that constant urge to pee. Pelvic tilts and gentle stretching can ease some of the discomfort.

Round ligament pain — those sharp, sudden pains on one or both sides of your lower belly — may still be making appearances, especially when you change positions quickly. Moving more slowly when getting up from a chair or rolling over in bed can help prevent these jolts.

Common Questions at Week 31

Why can't I sleep even though I'm exhausted?

Third trimester insomnia is incredibly common. It's a combination of physical discomfort, hormonal changes, anxiety about the birth, and your baby's tendency to be most active right when you're trying to wind down. Try establishing a relaxing bedtime routine, limiting screen time before bed, and keeping your bedroom cool. If you're lying awake with racing thoughts, getting up to do something calming (like reading) for 20 minutes before trying again can help more than tossing and turning.

What are Braxton Hicks contractions and should I worry?

Braxton Hicks are your uterus practicing for labor. They feel like a tightening across your belly and are usually irregular, brief, and painless or mildly uncomfortable. They're normal and common from the second trimester onward. Call your provider if contractions become regular (every 10 minutes or closer), painful, or are accompanied by bleeding, fluid leaking, or lower back pain — these could be signs of preterm labor.

Is it normal for baby to move less as they get bigger?

Your baby isn't necessarily moving less — they're moving differently. As space gets tighter, those big kicks and somersaults turn into rolls, shifts, and pushes. You should still feel regular movement throughout the day. Continue doing kick counts, and if you notice a significant decrease in movement, contact your provider.

This Week's Tip

Practice deep breathing exercises to prepare for labor. Deep breathing isn't just a relaxation technique — it's a practical tool you'll use during contractions. Try this: breathe in slowly through your nose for four counts, hold for four counts, and exhale slowly through your mouth for six counts. Practice this for a few minutes each day. It helps lower your heart rate, reduce tension, and gives you something concrete to focus on. Many people find that the breathing techniques they practice now become instinctive during labor.

Sources

• American College of Obstetricians and Gynecologists (ACOG) — Third Trimester
• Mayo Clinic — Fetal Development: The Third Trimester

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