Third Trimester
Medically reviewed by Samantha L. Fox, RN, BSN, MSN
Nursing Informaticist · United States Navy Nurse Corps · Last reviewed
Weeks 28–42 · The Home Stretch
You're in the home stretch! The third trimester is all about your baby putting on weight and getting ready for the big debut. Appointments become more frequent, your body feels the weight of a full-term pregnancy, and you're preparing everything for baby's arrival. It's equal parts exciting and exhausting — and the finish line is in sight.
Explore by Week
Key Milestones
Third Trimester Begins
Appointments shift to every 2 weeks. If you're Rh-negative, you'll receive the RhoGAM injection. Baby can now sense light and hear clearly.
Rapid Weight Gain
Baby gains about half a pound per week during this stretch. The lungs are maturing and the brain is developing complex folds.
Head-Down Position
Most babies turn head-down by week 32-36. Your doctor will check position at every visit. A baby still breech at 36 weeks may need a version attempt or planned C-section.
Group B Strep Test
A simple swab test for GBS bacteria. About 25% of women carry GBS. If positive, you'll receive IV antibiotics during labor to protect baby.
Weekly Appointments Begin
You'll now see your provider every week. Cervical checks begin to monitor dilation and effacement.
Early Term
Baby is considered early term. Brain and lung development continue until 39 weeks, so waiting for natural labor (when safe) is usually recommended.
Full Term & Due Date
Full-term babies have completed development and typically thrive at birth. Only about 5% arrive on the exact due date — most come within 2 weeks either way.
Overdue Monitoring
Doctors monitor closely with non-stress tests. Most will recommend induction by 41-42 weeks to reduce risks associated with post-term pregnancy.
Third Trimester Symptoms
Braxton Hicks Contractions
Irregular practice contractions that tighten your abdomen. They're usually painless and irregular — unlike real labor contractions.
Pelvic Pressure & Lightning Crotch
As baby drops into position, you may feel sharp shooting pains in the pelvis — nicknamed 'lightning crotch.' Uncomfortable but normal.
Shortness of Breath
Baby pressing on your diaphragm makes deep breaths harder. This usually improves after baby 'drops' (lightening).
Frequent Urination
Baby's head pressing on your bladder means frequent bathroom trips return with a vengeance.
Swelling (Edema)
Mild swelling in feet and ankles is normal. Sudden severe swelling, especially in the face/hands, warrants a call to your provider.
Insomnia
Hard to get comfortable! A pregnancy pillow helps. Try sleeping on your left side to improve circulation.
Heartburn
At peak intensity as baby squishes your stomach. Eat small meals, avoid lying down after eating, and ask your provider about safe antacids.
Nesting Instinct
An urge to clean, organize, and prepare — this is biologically normal! Channel it productively but don't overdo it.
Signs of Labor
Water Breaking
A gush or trickle of clear fluid — call your provider immediately. Many labors don't start with water breaking.
Bloody Show
Passage of the mucus plug, possibly tinged with blood. Can happen days before labor or as labor begins.
Regular Contractions
Unlike Braxton Hicks, real labor contractions get progressively stronger, longer, and closer together. Follow the 5-1-1 rule.
Lower Back Pain
Persistent lower back pain that radiates to the front, especially with a pattern, can indicate labor.
Nausea & Diarrhea
The body often clears itself out before labor begins. Some women experience nausea or loose stools.
🏥 Use our Contraction Timer to track contractions and know when to head to the hospital.
Third Trimester To-Do List
Clinical Context for the Third Trimester
The third trimester runs from week 28 through delivery, with full term defined as 39+0 through 40+6 weeks (ACOG). Prenatal visit cadence steps up — every 2 weeks from 28-36 weeks, then weekly from week 36 to delivery. Surveillance intensifies because this is the window where preeclampsia, gestational hypertension, preterm labor, and reduced fetal movement become the dominant clinical concerns.
Daily kick counts are recommended starting at 28 weeks per ACOG Practice Bulletin No. 229. The standard target is 10 movements within 2 hours; most babies reach this within 30 minutes when active. Significant or sustained decrease in movement is a reason to call your provider — not after a delay, the same day. Decreased fetal movement is one of the few warning signs you can reliably monitor at home.
Group B Streptococcus (GBS) screening is performed between 36+0 and 37+6 weeks per ACOG Committee Opinion No. 797. About 10-30% of pregnant women carry GBS asymptomatically; intrapartum antibiotic prophylaxis (typically IV penicillin every 4 hours during labor) reduces early-onset neonatal GBS disease by ~80%. Women with prior GBS-affected infants, GBS bacteriuria in current pregnancy, or unknown status with risk factors get prophylaxis regardless of swab result.
Preeclampsia surveillance escalates in the third trimester. Blood pressure and urine protein are checked at every visit. New-onset hypertension after 20 weeks (systolic ≥140 OR diastolic ≥90 on two readings 4 hours apart) with proteinuria — or with severe features (BP ≥160/110, low platelets, elevated liver enzymes, kidney dysfunction, pulmonary edema, persistent headache or vision changes) — meets diagnostic criteria per ACOG Practice Bulletin No. 222. Severe features mandate delivery regardless of gestational age.
Signs of labor include regular contractions that get stronger and closer together (the classic 5-1-1 rule: contractions every 5 minutes, lasting 1 minute, for 1 hour, for first-time moms), rupture of membranes (sudden gush or slow leak), bloody show, or persistent low back pain that radiates. ACOG Practice Bulletin No. 217 covers PROM management; report any fluid leak immediately so timing of delivery vs. expectant management can be assessed.
When to call your provider in the third trimester (or go to L&D):regular painful contractions, water breaks (clear or any color), bleeding more than spotting, severe headache with vision changes, sudden swelling of face or hands, upper-abdominal pain, decreased fetal movement, fever, or anything that makes you think "this is wrong." In labor evaluation, your instinct is data — providers would rather see you and send you home than miss something.
📚Clinical Sources & References
The calculations and guidance on this page are based on current clinical standards and peer-reviewed research. Reviewed by Samantha L. Fox, RN, BSN, MSN — Emergency Department nurse and US Navy Nurse Corps officer.
- [1]ACOG Practice Bulletin No. 229: Antepartum Fetal Surveillance. Obstet Gynecol. 2021;137(6):e116-e127.
- [2]ACOG Committee Opinion No. 797: Prevention of Group B Streptococcal Early-Onset Disease in Newborns. Obstet Gynecol. 2020;135(2):e51-e72.
- [3]ACOG Practice Bulletin No. 222: Gestational Hypertension and Preeclampsia. Obstet Gynecol. 2020;135(6):e237-e260.
- [4]ACOG Practice Bulletin No. 217: Prelabor Rupture of Membranes. Obstet Gynecol. 2020;135(3):e80-e97.
- [5]ACOG Practice Bulletin No. 107: Induction of Labor. Obstet Gynecol. 2009;114(2 Pt 1):386-397.
- [6]AAP & ACOG. Guidelines for Perinatal Care, 8th Edition. American Academy of Pediatrics; 2017.