TL;DR
- The third trimester is weeks 28-40 — the final stretch before you meet your baby.
- Your baby gains most of their weight now, going from about 2 pounds to an average of 6-9 pounds at birth.
- Discomfort increases — heartburn, back pain, insomnia, and Braxton Hicks are all common.
- This is when you prepare: pack your hospital bag, write a birth plan, install the car seat, and know the signs of labor.
What's Happening With Your Baby
Weeks 28-31: Gaining Weight
Your baby's brain is developing rapidly. The lungs are maturing but aren't quite ready yet. Baby is practicing breathing movements, hiccupping, and developing a more regular sleep-wake cycle. You'll notice patterns in when your baby is active and quiet.
Weeks 32-35: Getting Ready
Your baby is running out of room and may settle into a head-down position. Fat layers fill out under the skin, making baby look less wrinkled. The bones of the skull remain soft and flexible for delivery. Lungs continue to mature — babies born at 34+ weeks usually do well, though they may need some extra support.
Weeks 36-40: Full Term
At 37 weeks, your baby is considered "early term." At 39 weeks, "full term." Baby drops lower into your pelvis (called "lightening" or "engaging"), which makes breathing easier but puts more pressure on your bladder. The average baby at birth is about 7.5 pounds and 19-21 inches long.
What You Might Feel
Physical Symptoms
- Heartburn — Your growing uterus pushes your stomach upward. Eating smaller, more frequent meals helps.
- Back pain — The extra weight plus loosened ligaments equals an achy back. Prenatal massage, support belts, and gentle stretching can help.
- Swelling — Mild swelling in feet and ankles is normal. Sudden swelling in your face or hands needs immediate medical attention (it can be a sign of preeclampsia).
- Shortness of breath — Baby is crowding your lungs. This usually improves when baby drops.
- Insomnia — Between the discomfort, bathroom trips, and anxiety, sleep can be elusive. See our pregnancy insomnia guide.
- Braxton Hicks contractions — Practice contractions that are irregular and don't get stronger. See our Braxton Hicks vs. real contractions guide.
- Pelvic pressure — As baby drops, you may feel heavy pressure in your pelvis. Waddling is not optional.
- Frequent urination — Back with a vengeance as baby presses directly on your bladder.
Emotional Landscape
- Nesting instinct — A sudden urge to clean, organize, and prepare. Channel it, but don't overdo it.
- Anxiety about labor — Completely normal. Childbirth classes and talking to your provider can help.
- Impatience — Especially past your due date. Remember that due dates are estimates, not expiration dates.
- Emotional sensitivity — You might cry at everything. Hormones plus anticipation plus discomfort is a lot.
Prenatal Care
More Frequent Visits
Your appointment schedule ramps up:
- Weeks 28-36: Every 2 weeks
- Weeks 36-40: Every week
What Your Provider Is Watching
- Blood pressure — To screen for preeclampsia
- Baby's position — Confirming head-down by 36 weeks
- Fundal height — Measuring growth
- Group B Strep test — A vaginal/rectal swab around weeks 36-37. About 25% of people carry GBS bacteria. If positive, you'll receive antibiotics during labor.
- Cervical checks — Your provider may start checking for dilation and effacement in the final weeks (this is optional and you can decline)
Kick Counts
Starting around week 28, your provider may ask you to do daily kick counts. Pick a time when your baby is typically active and count how long it takes to feel 10 movements. Most babies hit 10 within 30 minutes to 2 hours. If you notice a significant decrease in movement, contact your provider.
Preparing for Birth
Things to Do
- Pack your hospital bag by 35-36 weeks — see our checklist
- Write a birth plan — see our template
- Install the car seat — Many fire stations and hospitals offer free inspections
- Tour the hospital or birth center — Know where to go and where to park
- Discuss pain management options with your provider — epidural, nitrous oxide, natural methods
- Know the signs of labor and when to head to the hospital
- Arrange help for after birth — Meals, childcare for other kids, household support
- Decide on pediatrician — Many providers recommend choosing one before delivery
When Is Labor Coming?
Common signs that labor may be approaching (days to weeks before):
- Baby drops lower in your pelvis
- Increased Braxton Hicks
- Losing your mucus plug
- Nesting urge intensifies
- Loose stools
- Lower back pain
Signs of actual labor:
- Regular contractions that get closer together and don't stop with rest
- Water breaking
- See our full signs of labor guide
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When to Call Your Provider Immediately
- Contractions every 5 minutes for 1 hour (or your provider's specified interval)
- Your water breaks
- Vaginal bleeding (more than spotting)
- Severe headache that won't go away
- Vision changes
- Sudden severe swelling
- Baby's movement decreases significantly
- Fever over 100.4F
- Any feeling that something is wrong — trust your instincts
Past Your Due Date
About 50% of first-time parents go past their due date. It's frustrating, but it's normal. Your provider will monitor you more closely after 40 weeks and will discuss options for induction, usually recommended between 41-42 weeks depending on your situation.
The Bottom Line
The third trimester is a marathon of waiting, preparing, and growing increasingly uncomfortable. It's also the home stretch — the last weeks before your life changes forever. Focus on rest, preparation, and being kind to yourself. You're almost there.
