The third trimester can feel like a countdown with a body that has its own mind: a heavier belly, lighter sleep, and a baby who seems to do somersaults right when you finally lie down. Many parents in India also juggle extra practical questions—festival travel, long commutes, family advice coming from all sides, and which symptoms mean “wait and watch” versus “call the doctor now”. The third trimester is also when check-ups often become more frequent, and decisions (birth preferences, hospital choice, support person) start to feel real.

What typically changes week by week in the third trimester? What is medical, what is just uncomfortable, and what needs a prompt call? Let’s make it straightforward.

Third trimester basics: timing, due date language, and “term”

The third trimester usually starts at 28 weeks of gestational age and continues until birth.

Doctors count pregnancy using gestational age (GA), measured from the first day of the last menstrual period. Your estimated due date (EDD) is around 40 weeks GA, but it is not a fixed “expiry date”. A healthy baby may arrive before or after it—commonly between 38 and 42 weeks.

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You may also hear “weeks since conception”, which is about two weeks less than GA. Same pregnancy, different counting.

“Viability” means the baby has a reasonable chance of surviving outside the uterus with intensive newborn care. Many centres discuss this around 24 weeks GA, and outcomes improve steadily—especially after 28 weeks, when lung and brain maturation speed up.

Term definitions (useful for planning and monitoring):

Early term: 37+0 to 38+6
Full term: 39+0 to 40+6
Late term: 41+0 to 41+6
Post-term: 42+0 and beyond

Third trimester weeks: what often changes by stage

Every pregnancy is unique. Still, the third trimester often follows a familiar pattern.

Weeks 28–31: early third trimester milestones

Baby is gaining weight fast, building subcutaneous fat, and improving coordination. Lungs mature quickly as surfactant production rises (surfactant helps tiny air sacs stay open after the first breaths).

You may notice:

Heartburn and bloating (progesterone slows digestion)
Breathlessness with activity
Backache and sleep disruption
More Braxton Hicks tightenings (often irregular, may settle with rest and hydration)

Common planning steps:

Discuss your visit schedule
Consider Tdap vaccination timing (often 27–36 weeks, as per local guidance)
Start noticing baby’s daily movement rhythm

Weeks 32–34: crowded uterus, stronger movements

Movements can feel stronger but less “flippy”—more rolls, stretches, and jabs. Many babies spend more time head-down, though position can still change.

You might feel:

Pelvic pressure
More night-time urination
Stronger reflux

In many Indian care settings, an ultrasound around this time may check:

Estimated fetal weight and growth curves
Placenta location
Amniotic fluid (AFI or deepest pocket)
Presentation (head-down/breech)

If there are specific risks, your doctor may suggest extra monitoring such as NST, BPP, or Doppler studies.

Weeks 35–37: key tests and final prep

This window often includes the GBS swab (35–37 weeks) where screening is offered. If positive, antibiotics during labour reduce the risk of early newborn infection.

Appointments may shift to weekly. Your team also checks baby’s presentation—head-down versus breech.

Braxton Hicks can become frequent. A helpful question: do they stay irregular and ease with rest? That points more to practice contractions.

Weeks 37–40+: term weeks and “any day now”

From 37 weeks, pregnancy is considered term. Baby continues to gain weight, engagement (baby settling deeper into the pelvis) can make the pelvis feel heavy.

Many parents notice:

Increased discharge
On-and-off bursts of energy, then fatigue
Even more fragmented sleep

If you cross your due date, closer monitoring (often NST/BPP and fluid checks) may be suggested, along with a discussion on induction timing.

Baby development in the third trimester: what is happening inside

The third trimester is less about building organs from scratch and more about maturing systems that will run independently after birth.

Growth and body fat

From week 28 onwards, weight gain accelerates. Ultrasound estimates are based on measurements (head, abdomen, femur length) plotted on growth curves—useful estimates, not a direct weighing.

Brain and nervous system maturation

The third trimester is a peak period for brain growth. Myelination (insulating nerve pathways) and rapid wiring support feeding coordination, reflexes, and sleep–wake rhythms.

Lung development

Lungs increase surfactant and practise breathing movements in amniotic fluid. Earlier birth may need respiratory support, later third trimester births tend to have more lung readiness.

Passive immunity (IgG transfer)

Maternal IgG antibodies cross the placenta more in late pregnancy, giving baby temporary protection after birth. Vaccination during pregnancy can strengthen this transfer.

Skin changes: vernix and lanugo

Vernix caseosa coats and protects baby’s skin. Lanugo (fine hair) usually thins towards term. Increasing fat also supports temperature regulation.

Placenta and amniotic fluid

Amniotic fluid depends largely on baby’s swallowing and urination. Too little (oligohydramnios) or too much (polyhydramnios) can lead to closer follow-up.

Baby position: head-down, breech, transverse

Many babies settle head-down (cephalic) during the third trimester. If baby remains breech near term, your doctor may discuss ECV (external cephalic version) around 36–37 weeks, depending on placenta position, fluid levels, and overall safety.

Baby movement in the third trimester: what’s normal and how to track it

As space gets tighter, you may feel fewer big flips but stronger rolls and stretches. Movement should remain present and recognisable.

Kick counts: a simple method

A commonly used approach is 10 movements in 2 hours:

Choose a time baby is usually active (often after meals)
Sit quietly or lie on your left side
Count distinct movements (kicks, rolls, swishes)

Many babies reach 10 much sooner. The point is noticing your baby’s usual pattern.

Decreased fetal movement: when to call

If you feel a persistent drop from your baby’s normal pattern, or you cannot feel 10 movements in 2 hours, call promptly.

You may be offered:

NST (heart rate response to movement)
BPP (ultrasound + NST, looks at breathing movements, tone, movement, and fluid)
Ultrasound checks of growth, placenta, fluid, and position

Common third trimester symptoms and what can help

Why does the third trimester feel so physical? Mechanical pressure, hormones, and circulation changes combine.

Fatigue and anaemia

Fatigue is common, but iron deficiency anaemia can make it worse. If blood tests show low haemoglobin or ferritin, iron supplementation may be advised.

Shortness of breath and rib pressure

The diaphragm has less room. Sit upright, pace activity, and try side-sleeping.

Seek urgent care for chest pain, fainting, or sudden severe breathlessness.

Heartburn and indigestion

Progesterone relaxes the valve between the oesophagus and stomach, and the uterus increases pressure. Helpful steps:

Smaller, more frequent meals
Avoid lying down for 2–3 hours after eating
Slight elevation of upper body at night

Ask your doctor about pregnancy-appropriate antacids such as calcium carbonate if needed.

Pelvic pressure and “lightening”

When baby descends, you may feel heaviness and more urinary frequency. Side-lying rest, short breaks, and a support belt (if advised) can help.

Back pain, ligament discomfort, pubic pain

Posture changes and ligament laxity contribute. Heat/cold packs, supportive footwear, and prenatal physiotherapy are often useful.

Avoid NSAIDs unless your clinician approves.

Swelling (oedema), heavy legs, varicose veins

Mild ankle/foot swelling is common in the third trimester. Walking, leg elevation, and hydration help, compression stockings may help if advised.

Call urgently if swelling is sudden (face/hands), or if there is severe headache or vision change (possible preeclampsia). One-sided leg swelling with pain/redness needs urgent assessment (possible clot).

Constipation and haemorrhoids

Fibre, fluids, and gentle daily movement are first-line. Sitz baths and clinician-approved creams can soothe haemorrhoids.

Urinary frequency and small leaks

Bladder pressure increases. Small leaks with coughing/sneezing are common. Burning, fever, or foul-smelling urine suggests UTI—call promptly.

Hand tingling: carpal tunnel symptoms

Fluid shifts can trigger carpal tunnel syndrome symptoms (tingling, numbness). Wrist splints at night and hand elevation can help.

Sleep and emotional load

Sleep may be lighter, with vivid dreams. Worry can also rise—especially close to delivery. If anxiety becomes overwhelming, or mood feels very low, discuss it with your obstetrician, support and counselling options exist.

Third trimester comfort strategies: sleep, food, movement

Sleep set-up

Side-sleeping is generally preferred in late pregnancy. Use pillows:

Between knees
Under the belly
Behind the back (to prevent rolling flat)

If you wake up on your back, roll to your side—no panic.

Eating and key nutrients

The goal is steady nutrition, not “eating for two”. Common focuses in the third trimester:

Iron (especially if anaemia is present)
Calcium (preferably from food)
Omega-3 (DHA) as part of a balanced diet

If you take both iron and calcium supplements, separating them can improve absorption.

Medicines and OTC remedies

Avoid self-medicating. Some anti-inflammatory medicines (like ibuprofen) are usually avoided in the third trimester. Share a full list of supplements and OTC products with your doctor.

Gentle exercise

If your pregnancy is uncomplicated, walking, swimming, prenatal yoga, and light stretching can support sleep, circulation, and mood.

Stop and seek advice for bleeding, leaking fluid, regular contractions, faintness, or decreased fetal movement.

Sex in the third trimester

In an uncomplicated pregnancy, sex is generally safe. Comfort is the guide—side-lying positions often help.

Seek advice if there is bleeding, leaking fluid, placenta previa, or risk of preterm labour.

Prenatal care in the third trimester: visits and routine checks

Many clinics schedule visits every 2 weeks from 28–32 weeks, then weekly from around 36 weeks until delivery.

Typical checks:

Blood pressure
Weight trends
Urine testing when used (protein, infection)
Symptom review
Fetal heart rate (often 110–160 bpm)

Growth assessment

Fundal height (cm from pubic bone to top of uterus) often roughly matches weeks of pregnancy. If it is smaller/larger than expected, ultrasound may evaluate growth, placenta, fluid, and position.

Cervical checks

Cervical checks may be offered closer to term or if labour is suspected. They can assess dilation/effacement, but they do not reliably predict when labour will start.

Third trimester tests and screenings

Depending on your pregnancy and local practice:

Glucose testing follow-up for gestational diabetes (OGTT if needed)
GBS screening (where offered)
CBC for anaemia (often haemoglobin <11 g/dL in the third trimester)
RhIG around 28 weeks if you are Rh-negative and not sensitised

Monitoring: when extra testing is used

Extra monitoring may include:

Ultrasound for growth, placenta location, fluid, and presentation
NST
BPP
Umbilical artery Doppler when placental insufficiency or growth restriction is suspected

Vaccines in the third trimester

Depending on timing and local guidance, you may be offered:

Tdap (often 27–36 weeks)
Flu vaccine
COVID-19 vaccine/booster
Maternal RSV vaccine (in some settings)

These support protection for the pregnant person and increase transplacental IgG transfer to the baby.

Skin changes: itching, stretch marks, rashes

Dry, stretched skin can itch. Moisturiser and cool compresses help.

Call promptly if itching is intense, worse at night, and especially if it involves palms and soles or is paired with dark urine or yellowing of eyes/skin (possible intrahepatic cholestasis of pregnancy, needs bile acid testing).

Warning signs in the third trimester: when to call or go in

Contact your maternity unit urgently for:

Vaginal bleeding
Suspected waters breaking (gush or continuous leak)
Regular painful contractions before 37 weeks
Decreased fetal movement
Fever or chills
Severe headache, vision changes, right upper belly pain
Sudden swelling of face/hands
One-sided leg swelling with redness or pain
Chest pain, fainting, severe breathlessness

Labour signs: telling true labour from Braxton Hicks

Braxton Hicks: often irregular, may ease with rest, hydration, warmth, or position change.

True labour: becomes regular, closer, longer, stronger—and changes the cervix.

A common timing guide is 5-1-1 (5 minutes apart, 1 minute long, for 1 hour), but follow your hospital’s instructions.

If waters break, note time, colour (clear versus green/brown), smell, and baby’s movement pattern, then call.

Preparing for birth in the third trimester

The third trimester is a good time to keep plans simple and flexible.

Birth preferences: support person, comfort measures, pain relief options (including epidural anaesthesia)
Induction: may be offered for post-term pregnancy, ruptured membranes without labour, preeclampsia, diabetes-related concerns, or fetal growth concerns
Breech baby: discuss ECV around 36–37 weeks if appropriate
Hospital bag: many parents pack between 32–36 weeks, include documents, clothes, pads, baby clothes, and a properly installed car seat
Logistics: plan transport (especially at night), childcare for older children, and who to call first

To remember

The third trimester starts at 28 weeks and continues until birth, “term” has specific week ranges.
Baby gains fat, matures brain and lungs, and benefits from increasing IgG antibodies.
In the third trimester, movements may feel different, but they should stay present, reduced movement is a strong reason to call.
Warning signs—bleeding, leaking fluid, fever, severe headache/vision changes, sudden swelling, intense palm/sole itching, or contractions before 37 weeks—need prompt medical attention.

If you feel unsure, your obstetrician, midwife, or maternity unit can guide you. You can also download the Heloa app for personalised tips and free child health questionnaires for children.

Third trimester: week-by-week timeline and what to expect