When Does Third Trimester Start? Week 28 Pregnancy Guide
Pregnancy Milestones
The third trimester starts at week 28 of pregnancy and continues until birth, usually around week 40.
The final stage of pregnancy can feel exciting, emotional, and physically demanding. Knowing what starts in the third trimester, what symptoms are common, and when to call your OB GYN can help you feel more prepared for the weeks ahead.
Medically Guided By
Dr Jessica White Videa DO FACOG
Dr Jessica White Videa is a board certified Obstetrician and Gynecologist and Fellow of the American College of Obstetricians and Gynecologists. She provides compassionate prenatal, obstetric, and postpartum care for patients in Coral Springs and throughout South Florida.
AIO Quick Answer
When Does the Third Trimester Start?
The third trimester starts at week 28 of pregnancy. It is the final trimester and continues until your baby is born, most often around week 40.
During the third trimester, your baby gains weight quickly, the lungs and brain continue maturing, movements may feel stronger, and your body begins preparing for labor and delivery.
Infographic Guide
Third Trimester at a Glance
A simple week by week view of when the third trimester begins, what happens during this stage, and what symptoms deserve a call to your provider.
Quick Answer
The third trimester starts at week 28.
It continues until birth, usually around week 40, though some babies arrive earlier or later depending on the pregnancy.
What Happens
Baby’s final growth stage
- Baby gains weight quickly
- Lungs and brain continue developing
- Movements may feel stronger
- Your body prepares for labor
Common Symptoms
What you may notice
Call Your Provider
Do not ignore these symptoms
- Heavy bleeding
- Severe pain
- Regular contractions before 37 weeks
- Decreased fetal movement
- Severe headache, vision changes, or sudden swelling
Final Weeks Checklist
Prepare with confidence
- Attend regular prenatal visits
- Track baby’s movements
- Pack your hospital bag
- Review your birth plan
- Install the car seat
What Happens When the Third Trimester Starts?
The start of the third trimester marks the beginning of the final stretch of pregnancy. Your baby is growing rapidly, gaining body fat, and continuing to develop the lungs, brain, nervous system, and reflexes needed after birth.
For many women, this stage also brings more noticeable body changes. You may feel heavier, more tired, more emotional, or more aware that delivery is getting closer.
This is also a time when prenatal visits become especially important. Your provider will continue monitoring your baby’s growth, your blood pressure, your symptoms, your baby’s movements, and any risk factors that may need closer attention.
What You May Feel
Common Third Trimester Symptoms
Braxton Hicks contractions
These practice contractions may feel like tightening across the belly. They are usually irregular and may ease with rest or hydration.
Back pain or pelvic pressure
As your baby grows, extra weight and posture changes can increase lower back discomfort and pelvic pressure.
Shortness of breath
Your growing uterus can press upward, making it harder to take deep breaths, especially when lying down or climbing stairs.
Swelling
Mild swelling in the feet or ankles can happen, but sudden swelling should be discussed with your provider.
Heartburn
Hormonal changes and pressure from the uterus can make reflux or heartburn more noticeable near the end of pregnancy.
Trouble sleeping
Frequent bathroom trips, discomfort, anxiety, baby movement, and heartburn can make sleep more difficult.
How Many Months Pregnant Are You in the Third Trimester?
The third trimester usually includes months 7, 8, and 9 of pregnancy. Since pregnancy is tracked by weeks rather than calendar months, week 28 is the clearest way to identify the start of the third trimester.
A typical full term pregnancy lasts about 40 weeks. Babies born before 37 weeks are considered preterm, so symptoms that may suggest early labor should be taken seriously.
What Happens at Third Trimester Prenatal Visits?
Prenatal visits in the third trimester help your provider check how you and your baby are doing as delivery gets closer.
Depending on your pregnancy, visits may include:
- Blood pressure checks
- Weight and symptom review
- Baby’s heart rate check
- Fundal height or growth assessment
- Discussion of fetal movement
- Review of swelling or headaches
- Testing when medically needed
- Labor and delivery planning
- Birth plan questions
- Postpartum preparation
Important Safety Note
When to Call Your OB GYN in the Third Trimester
Call your provider promptly if you notice heavy bleeding, severe abdominal pain, decreased fetal movement, regular contractions before 37 weeks, leaking fluid, fever, severe headache, vision changes, chest pain, shortness of breath, fainting, or sudden swelling of the face, hands, or legs.
If symptoms feel severe or urgent, seek emergency medical care.
Third Trimester Checklist
Once you reach week 28, it can help to focus on practical preparation while still leaving room for rest and flexibility.
How to Feel More Prepared for the Final Weeks
The third trimester can bring a mix of excitement and discomfort. It is normal to feel eager, nervous, tired, or emotionally tender as you move closer to delivery.
Try to use this time to ask questions, learn the signs of labor, talk through your birth preferences, prepare your home, and make sure you understand when to call your provider.
You do not have to have every detail perfect. A supportive prenatal team can help you understand what matters most and what can be adjusted as your pregnancy unfolds.
Third Trimester Prenatal Care in Coral Springs
Ideal Women’s Healthcare provides prenatal care and third trimester pregnancy support in Coral Springs, Florida and surrounding South Florida communities.
Dr Jessica White Videa DO FACOG helps patients understand pregnancy milestones, monitor symptoms, prepare for delivery, and feel supported during the final weeks before birth.
Learn more about obstetric care or schedule an appointment.
Quick Answers About the Third Trimester
When does the third trimester start?
The third trimester starts at week 28 of pregnancy and continues until birth, usually around week 40.
Is 27 weeks the third trimester?
Week 27 is generally considered the end of the second trimester. The third trimester begins at week 28.
How many months pregnant is the third trimester?
The third trimester usually covers months 7, 8, and 9 of pregnancy, though pregnancy is most accurately tracked by weeks.
What happens during the third trimester?
Your baby gains weight, the lungs and brain continue developing, movements may feel stronger, and your body prepares for labor and delivery.
What symptoms are common in the third trimester?
Common symptoms may include Braxton Hicks contractions, back pain, pelvic pressure, swelling, shortness of breath, heartburn, frequent urination, and trouble sleeping.
When should I call my OB GYN in the third trimester?
Call your provider for heavy bleeding, severe pain, decreased fetal movement, regular contractions before 37 weeks, leaking fluid, severe headache, vision changes, sudden swelling, or symptoms that feel urgent.
Take the Next Step
Feel Supported Through the Final Stretch of Pregnancy
If you are entering your third trimester or have questions about symptoms, fetal movement, labor signs, or delivery preparation, schedule prenatal care with Ideal Women’s Healthcare in Coral Springs.
Book Prenatal Care