The third trimester — Week 28 to Week 40 (and sometimes beyond) — is the final and most anticipated phase of pregnancy. The baby gains weight rapidly, and you get mentally and physically ready for delivery. Below is a detailed breakdown of each week.
(This article is the next and final part of our Pregnancy Calendar Week by Week overview and our Second Trimester Guide.)
Week 28: The Start of the Third Trimester
- Baby’s Growth (size: eggplant): The baby’s eyes start opening and closing, and the baby now enters the REM sleep cycle.
- Your Changes: Third trimester checkups now happen every 2 weeks.
- Tip: Follow your antenatal appointment schedule — don’t miss any.
Week 29: Muscles and Lungs Are Developing
- Baby’s Growth (size: butternut squash): The baby’s muscles and lungs continue to develop.
- Your Changes: You may feel shortness of breath as the uterus puts pressure on your lungs.
- Tip: Sitting upright makes breathing a bit easier.
Week 30: The Brain Is Rapidly Developing
- Baby’s Growth (size: cabbage): The baby’s brain is developing rapidly, and they’re learning to regulate temperature.
- Your Changes: Back pain and fatigue may increase.
- Tip: Sleeping on your left side improves blood flow — a pregnancy pillow can help.
Week 31: The Baby’s Weight Increases Quickly
- Baby’s Growth (size: coconut): The baby’s weight now starts increasing rapidly — significant gain happens each week.
- Your Changes: Frequent urination may increase again.
- Tip: Start packing your hospital bag — it’s better to be ready early.
Week 32: Bones Are Hardening
- Baby’s Growth (size: squash): The baby’s bones are hardening (except the skull, which stays soft for delivery).
- Your Changes: Braxton Hicks contractions may become more frequent.
- Tip: Note the pattern of your contractions — if they become regular and painful, tell your doctor.
Week 33: The Immune System Is Strengthening
- Baby’s Growth (size: pineapple): The baby’s immune system is strengthening — they’re receiving antibodies from you.
- Your Changes: Sleeping may become difficult — finding a comfortable position becomes challenging because of the bump.
- Tip: Use pregnancy-safe pillows to try multiple sleeping positions.
Week 34: The Vernix Coating Thickens
- Baby’s Growth (size: cantaloupe): The baby’s protective vernix coating thickens, and the lungs are almost mature.
- Your Changes: Pelvic pressure may increase as the baby shifts downward.
- Tip: Get your birth plan and hospital documents ready.
Week 35: Kidneys Are Fully Developed
- Baby’s Growth (size: honeydew melon): The baby’s kidneys are fully developed, and the liver is functioning fairly well too.
- Your Changes: Weekly doctor visits may begin.
- Tip: The GBS (Group B Streptococcus) test usually happens around this week — confirm with your doctor.
Week 36: Moving Into Birth Position
- Baby’s Growth (size: romaine lettuce): The baby starts moving into the head-down (birth) position.
- Your Changes: You may feel “lightening” — as the baby shifts down, breathing becomes a bit easier but bladder pressure increases.
- Tip: It’s important to recognize the early signs of labor — be sure to read our guide: 5 Early Signs of Labor You Shouldn’t Ignore: A Compassionate Guide.
Week 37: Close to Full-Term
- Baby’s Growth (size: swiss chard bunch): The baby is now considered “early term,” and the lungs are quite mature.
- Your Changes: The cervix may start dilating (your doctor will check this at your appointment).
- Tip: Keep your hospital bag ready — labor could start anytime.
Week 38: The Baby Is Fully Ready
- Baby’s Growth (size: leek): All of the baby’s organs are functional, and they’re fully ready for birth.
- Your Changes: You may lose your mucus plug or notice spotting — a sign labor is getting close.
- Tip: Make sure your partner or family clearly knows the plan for getting to the hospital.
Week 39: Full Term
- Baby’s Growth (size: watermelon): You’re now officially “full term” — the baby could arrive any time.
- Your Changes: Contractions may become strong and regular if labor is starting.
- Tip: Track the timing of your contractions (duration and gap) and follow your doctor’s guidance on when to head to the hospital.
Week 40: Due Date — and Beyond
- Baby’s Growth: The baby is fully developed and ready to come into the world.
- Your Changes: If your due date passes, don’t worry — plenty of babies arrive even after 40 weeks. Your doctor will monitor you closely.
- Tip: Stay calm, double-check your hospital bag and documents, and make sure you have your support system with you.
Things to Keep in Mind During the Third Trimester
- ✅ Don’t miss weekly or bi-weekly doctor visits
- ✅ Learn to recognize the early signs of labor
- ✅ Keep your hospital bag and birth plan ready in advance
- ✅ Track the pattern of your contractions
According to WHO’s guidelines, regular monitoring during the third trimester helps track the health of both mother and baby more effectively.
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Related Reads
- Pregnancy Calendar Week by Week — Overview & Calculator
- Week 14 to 27: Second Trimester Detailed Guide
- 5 Early Signs of Labor You Shouldn’t Ignore: A Compassionate Guide
- Baby Health Essentials: Safe Sleep, Proper Nutrition & Hygiene for New Parents
FAQs
Regular contractions, water breaking, and mucus plug loss are common signs of labor. For full details, read this guide.
The third trimester runs from Week 28 to Week 40, and can sometimes extend up to Week 42.
Don’t worry — keep up with regular monitoring with your doctor. Many pregnancies deliver normally even after 40 weeks.
Disclaimer: This article is for general information purposes only and is not a substitute for medical advice. Always consult your gynecologist regarding your specific pregnancy condition.
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