Week 31 of Pregnancy
Learn about your baby's development and what to expect at 31 weeks pregnant.
Baby's Size This Week
Baby Development at Week 31
- ● Your baby now measures about 41.1 cm and weighs approximately 1502g.
- ● Rapid brain development continues, and the connections between brain cells (synapses) are forming at an extraordinary rate, supporting future learning and memory.
- ● Layers of fat continue to accumulate beneath the skin, now giving your baby a rounder, fuller appearance and improved ability to regulate body temperature.
- ● The eyes can open and close; your baby spends periods with eyes open during waking hours and can track slow-moving light.
- ● Your baby is practicing breathing movements using amniotic fluid for 30–40% of the time, a sign of healthy lung and diaphragm development.
- ● All five senses are functional — your baby can smell amniotic fluid (flavored by your diet), taste, hear, see light, and feel touch inside the womb.
Your Body at Week 31
- ● Shortness of breath is common as the baby moves higher and presses against the diaphragm — short, frequent walks rather than extended activity may be more comfortable.
- ● Swelling (edema) in feet, ankles, and hands is normal; elevate your legs when resting and reduce sodium intake.
- ● Sleep may become challenging — try a pregnancy pillow and sleep on your left side for better circulation.
- ● Braxton Hicks contractions may intensify and feel more uncomfortable — they are differentiated from true labor by their irregularity and cessation with rest.
- ● Pelvic girdle pain and symphysis pubis dysfunction (pain at the front of the pelvis) may develop or worsen as the hormone relaxin loosens the pelvic joints.
- ● Increased urination may return as the baby's head moves lower and puts additional pressure on the bladder.
Week 31 Checklist
- ☐ Attend prenatal visits every 2 weeks as scheduled in the third trimester.
- ☐ Practice relaxation and breathing techniques for labor preparation — consider a birth preferences worksheet to clarify your priorities.
- ☐ Finalize your birth preferences and discuss them with your care team, including your wishes for delayed cord clamping and skin-to-skin contact.
- ☐ Ensure your newborn essentials (infant car seat, bassinet, feeding supplies) are ready and car seat installation is scheduled.
- ☐ Begin packing your hospital bag: comfortable clothing, toiletries, phone charger, snacks, and items for the baby's first outfit and ride home.
- ☐ Research your postpartum recovery needs: pelvic floor physical therapy referrals, lactation support contacts, and meal prep or delivery options.
Frequently Asked Questions
What should I expect at 31 weeks pregnant?
At 31 weeks pregnant, you are in the third trimester with roughly 9 weeks until your due date. Your baby is about the size of a Coconut (41.1 cm) and is rapidly developing brain connectivity, fat stores, and sensory integration. Common symptoms include shortness of breath, swelling, pelvic pain, sleep difficulty, and more frequent Braxton Hicks contractions. Always consult your healthcare provider for personalized guidance.
How big is my baby at 31 weeks?
At week 31, your baby is approximately 41.1 cm in length and weighs around 1502g — roughly the size of a Coconut. These measurements are averages based on WHO fetal growth charts; individual babies vary naturally in size.
What is pelvic girdle pain and how is it treated?
Pelvic girdle pain (PGP) refers to pain in the joints of the pelvis — the sacroiliac joints at the back and the symphysis pubis at the front — caused by the hormone relaxin loosening the ligaments. It can range from mild discomfort to debilitating pain that affects walking. Treatment includes pelvic floor physical therapy, a support belt, avoiding asymmetric positions (like crossing legs or carrying weight on one hip), and sleeping with a pillow between the knees.
When should I start packing my hospital bag?
Most providers recommend having your hospital bag packed by 35–36 weeks, but packing it earlier (around week 32) ensures you are prepared if labor begins prematurely. Key items include: identification and insurance information, your birth plan, comfortable clothing, toiletries, phone charger, snacks for labor, a going-home outfit for baby, and a properly installed car seat in the vehicle.
Can I still exercise at 31 weeks pregnant?
Yes, regular physical activity in the third trimester is beneficial for managing weight gain, reducing back pain, improving sleep, and preparing for labor. ACOG recommends at least 150 minutes of moderate-intensity aerobic activity per week throughout pregnancy for those without contraindications. Safe options include walking, swimming, prenatal yoga, and stationary cycling. Avoid exercises that involve lying flat on your back, contact sports, or activities with a risk of falling.
Track Your Exact Pregnancy Week
Use our free Pregnancy Week Tracker to find out exactly how far along you are based on your last menstrual period or due date.
Track My Pregnancy →Sources
- ACOG
- WHO Fetal Growth Charts
- Mayo Clinic
Medical disclaimer: This content is for informational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider for guidance specific to your pregnancy.