The third trimester — weeks 28 through 40 — is the final chapter before you meet your baby. Your body prepares for labour, your baby gains half its birth weight, and both of you settle into a sleep-wake rhythm. Here is what to expect week by week and how to prepare for the big day.
Key milestones: Baby turns head-down (~week 32) · Early term from week 37, full term from week 39 · Brain grooves complete by week 35 · Expected due date at week 40
Weeks 28–30: Rapid Weight Gain Begins
Eyes open, bone marrow takes over
At week 28, your baby's eyes open for the first time and pupils react to light. Bone marrow fully takes over red blood cell production. Weight is ~1 kg. By week 29, the baby actively accumulates subcutaneous fat to prepare for temperature regulation after birth — drawing ~250 mg of calcium from your body every day. Braxton-Hicks practice contractions may become more noticeable.
Kick counting starts now: From week 28, count fetal movements daily. Set aside a time when your baby is typically active and count. You should feel at least 10 movements in 2 hours. Contact your doctor immediately if movements significantly decrease.
1.3–1.5 kg, stronger jabs
Space is running out. Your baby now weighs ~1.3–1.5 kg and can no longer swim freely, so movements feel like strong elbows and knees pressing outward. Amniotic fluid reaches its maximum volume this week and will gradually decrease from here. Colostrum — the antibody-rich first milk — may begin leaking from your breasts. Your weight gain may be at its fastest right now.
Weeks 31–34: Countdown to Term
Head down, skin smooth, nails grown
By week 32, most babies turn head-down (vertex position) — the ideal position for a vaginal birth. If yours has not, see breech baby: odds of turning and birth options. Skin is smoothing out and turning pink as fat fills in beneath it. Nails reach the fingertips. The immune system strengthens by absorbing your antibodies. Your uterus is now 11 cm above the navel; shortness of breath is a constant companion. Blood volume is 40–50% higher than before pregnancy.
Warning signs in the third trimester — call your doctor immediately if you experience: sudden swelling of face or hands, severe headache, visual disturbances, pain in the upper right abdomen (possible preeclampsia), vaginal bleeding, or a sudden significant decrease in fetal movement.
Sleep schedules and lung preparation
At week 33, your baby has a clear sleep-wake schedule — pupils close when sleeping, open when awake. Bones are hardening everywhere except the skull, which stays soft and movable for the birth canal. By week 34, the lungs are in their final preparation stage; the baby inhales and exhales amniotic fluid to strengthen breathing muscles. Vernix (protective coating) thickens to help with the birth. Weight: ~2.1–2.3 kg.
Weeks 35–37: Full Term Preparation
2.4–2.8 kg — lungs nearly ready
At week 35 your baby weighs ~2.4 kg. Most lanugo has disappeared; vernix is thick. The digestive system is ready, though feeding requires practice. By week 36, the lungs are nearly mature. The baby's head may engage (drop into the pelvis) — you'll feel less pressure on the ribs but more on the bladder. You may need to urinate every 30 minutes.
Week 37 = early term: A baby born at 37 weeks or later has lungs and organs considered ready for independent life and is unlikely to need neonatal intensive care. Weeks 37–38 are medically defined as "early term"; weeks 39–40 are "full term," which on average brings slightly better outcomes still.
Weeks 38–40: The Wait
Ready — just waiting for the signal
Your baby is fully ready. At week 40, average weight is 3.3–3.5 kg and length ~50 cm. The placenta will begin to age after week 41, which is why induction is often offered at 41–42 weeks. Your body is producing a surge of oxytocin, and the baby's cortisol helps trigger labour. Braxton-Hicks contractions may become stronger and more regular as the cervix softens and effaces.
How to Count Fetal Kicks
Regular kick counting is one of the simplest and most powerful tools for monitoring your baby's wellbeing in the third trimester. Here's the standard method:
- Choose a time when your baby is usually active (often after meals)
- Sit or lie comfortably and focus on movements
- Count kicks, rolls, jabs, or swishes — anything counts
- You should feel at least 10 movements in 2 hours
- If you don't reach 10 movements in 2 hours, call your midwife or maternity unit
- Never use alcohol or cold drinks to "wake up" the baby to get movement
Baby Novum has a built-in kick counter that records each movement, tracks the time taken, and stores your history so you can share it with your doctor.
Signs of Labour
- Regular contractions — unlike Braxton-Hicks, labour contractions get longer, stronger and closer together
- Waters breaking — a gush or trickle of fluid from the vagina (call your maternity unit immediately)
- Show — a plug of pink-tinged mucus (may happen days before labour starts)
- Backache — a continuous low dull ache, different from the usual back pain
- Nesting urge — a sudden burst of energy to clean and organise (often 24–48 hrs before labour)
Go to hospital immediately if: waters break, you have heavy bleeding, contractions are 5 minutes apart and lasting 1 minute, or you have sudden severe pain or pressure.
The full breakdown — including how to tell real contractions from Braxton-Hicks and the 5-1-1 rule — is in the signs of labour guide.
Third Trimester Checklist
- Pack your hospital bag by week 36 (see our full checklist)
- Count kicks daily from week 28 — know your baby's pattern
- Take the glucose tolerance test at week 28 (gestational diabetes screen)
- Continue iron, omega-3, calcium and magnesium supplements
- Attend all prenatal appointments (usually every 2 weeks from week 28, then weekly from week 36 — see the full visit-by-visit schedule)
- If you are having growth scans, ask for each estimate rather than only the latest — our guides to reading the report and growth percentiles explain why the trend matters more than any single number
- Write your birth plan and discuss with your midwife
- Practice breathing and relaxation techniques for labour
- Install the infant car seat and check it's fitted correctly
Swelling and disrupted sleep both peak in these weeks — the swelling guide covers which kind needs a same-day call, and sleep positions covers getting comfortable at this size. It is also worth reading the postpartum recovery guide now, while there is quiet time to do it. For any single week in this stretch, see the week-by-week guide.
FAQ — Third Trimester
When does the third trimester start and how long does it last?
The third trimester runs from week 28 through birth, typically around week 40, though anywhere from 37 to 42 weeks is within the normal range. It is the longest single stretch by symptom load — kick counts, more frequent appointments, and birth preparation all ramp up during these weeks.
How often will I see my care provider in the third trimester?
Appointments typically move to every two weeks from week 28, then weekly from week 36 onward for most care pathways. This increasing frequency is routine monitoring, not a response to any specific concern — it reflects how much changes for both of you in the final stretch.
What is the single most important daily habit in the third trimester?
Daily kick counts from week 28 onward. Reduced fetal movement is one of the strongest non-invasive warning signs available, and same-day assessment of reduced movement is associated with meaningfully better outcomes — it is worth treating as routine rather than optional.
How is "full term" different from being overdue?
A baby born from 37 weeks is early-term, and full term runs from 39 to 40 weeks 6 days — both are entirely normal outcomes, not early or overdue. "Overdue" more precisely means past 42 weeks, at which point care providers typically discuss induction; anywhere from 37 to 42 weeks is within the range care is designed around.