What Happens in the Third Trimester

Weeks 28-40 at a glance

In the third trimester the baby gains weight quickly, builds fat, and moves into a head-down position for most births. Common symptoms include shortness of breath, heartburn, frequent urination, swelling, trouble sleeping, and Braxton Hicks contractions.

Visits become more frequent so your provider can monitor blood pressure, growth, and the baby's position as your due date nears.

Third-trimester schedule and tests

Typical timing in weeks 28-40. Your provider sets your exact plan.

Item	When	What it does
Prenatal visits	Every 2 weeks	From about 28 to 36 weeks
Prenatal visits	Weekly	From about 36 weeks to delivery
Group B strep (GBS) test	36-37 wk 6 days	Vaginal and rectal swab; if positive, you get IV antibiotics during labor
Daily kick counts	From ~28 weeks	Track your baby's movement pattern at home

How to do kick counts

Counting movement helps you notice changes early:

• Pick a time when your baby is usually active, often after a meal.
• Sit or lie on your side and note the time.
• Count any movement, including kicks, rolls, jabs, and flutters.
• Time how long it takes to reach 10 movements; many babies reach 10 within about 2 hours.
• Do it around the same time daily so you learn your baby's normal pattern.
• Call your provider the same day if movement slows, stops, or changes from the usual pattern.

Braxton Hicks vs. real labor

How practice contractions differ from true labor.

Feature	Braxton Hicks	Real labor
Timing	Irregular, do not get closer together	Regular, come closer together over time
Strength	Stays mild	Gets stronger and more intense
With rest or position change	Usually ease or stop	Continue and progress
Location	Often felt in the front	Often start in the back and wrap around

Preparing for birth

• Confirm your provider's instructions for when to go to the hospital or call.
• Pack a bag for you and the baby by around 36 weeks.
• Install and have the car seat checked ahead of time.
• Discuss your birth preferences, pain relief options, and feeding plan with your provider.
• Know the signs of labor: regular contractions, your water breaking, and a bloody show.

Reflects ACOG group B strep and preeclampsia guidance and Cleveland Clinic/Mayo Clinic third-trimester guidance, 2024-2026.

Related questions

How often are prenatal visits in the third trimester?

Visits are usually every two weeks from about 28 to 36 weeks, then weekly from 36 weeks until delivery. Your provider may see you more often if you have high blood pressure, diabetes, or other concerns.

When is the group B strep test done and why?

GBS screening is done at 36 to 37 weeks and 6 days using a swab of the vagina and rectum. GBS is common and usually harmless to adults but can infect a newborn during birth. If you test positive, you receive IV antibiotics during labor to protect the baby.

When should I start counting kicks?

Most providers suggest starting around 28 weeks. Pick a consistent time, count any movements, and learn your baby's normal pattern. Contact your provider the same day if movement decreases or changes, rather than waiting.

How do I tell Braxton Hicks from real labor?

Braxton Hicks contractions are irregular, stay mild, and ease with rest or a change of position. Real labor contractions come at regular intervals, get closer together and stronger, and do not stop when you move. When in doubt, call your provider.

What are the warning signs of preeclampsia?

Preeclampsia signs include a severe or persistent headache, vision changes, sudden swelling of the face and hands, upper-right belly pain, and rapid weight gain, typically in the second half of pregnancy. Preeclampsia can be serious, so contact your provider right away if you have these symptoms.

Sources & further reading

1. Cleveland Clinic — Third Trimester of Pregnancy
2. ACOG — Group B Strep and Pregnancy (FAQ)
3. Cleveland Clinic — Kick Counts (Fetal Movement Counting)
4. Mayo Clinic — Preeclampsia: Symptoms & causes
5. ACOG — Preeclampsia and High Blood Pressure During Pregnancy (FAQ)

This article reflects current AAP, CDC, FDA, and other public-health guidance and is for educational purposes only. It does not constitute medical advice. ParentFlow is a wellness companion — not a substitute for your pediatrician. For any medical concern, contact your healthcare provider.