Pregnancy Week by Week Third Trimester: Best 28-40 Week Guide

Medical Disclaimer: This article is for informational purposes only and reviewed against WHO antenatal care guidelines. The third trimester requires close monitoring — always follow your gynaecologist’s specific guidance.

Pregnancy week by week third trimester is the phase where pregnancy stops being something you’re experiencing and starts being something you’re finishing.

My cousin described the third trimester as “the last month lasting approximately four years.” She said this at Week 34, while trying to find a comfortable position on the sofa, her feet elevated on three pillows, a hot water bottle on her back, and her phone in her hand alternating between Google searches for “natural labour induction” and “how to sleep when you can’t breathe properly.”

She delivered at Week 39, four hours of active labour, healthy baby. She now says the third trimester was the most important preparation for labour she went through — not because she did anything specific, but because by the end of it, she was so genuinely ready that the prospect of labour was a relief.

This guide covers the pregnancy week by week third trimester — everything happening with your baby and your body from Week 28 to Week 40, the essential final trimester tests, and what to prepare so that when labour begins, you are ready.

Pregnancy Week by Week Third Trimester — What This Phase Is

The pregnancy week by week third trimester runs from Week 28 to birth — typically Week 40, though full term is defined as anywhere from Week 37 to Week 42.

According to the World Health Organization’s antenatal care guidelines and FOGSI (Federation of Obstetric & Gynaecological Societies of India) clinical guidelines, the third trimester is when the most intensive antenatal monitoring occurs — blood pressure, fetal growth, fetal position, and the mother’s overall health are assessed at every visit. The Indian Academy of Pediatrics recommends that Indian pregnant women attend at minimum four antenatal visits during pregnancy, with at least one in the third trimester — though more frequent visits are standard practice.

What the third trimester is primarily about: Your baby is growing and maturing. The organs are formed — now they are completing their development, particularly the lungs and brain. Your body is preparing for labour. And you are preparing — emotionally, practically, and physically — for birth.

Week by Week — Third Trimester

Week 28 — The Third Trimester Begins

Baby size: Aubergine/Brinjal (approximately 37.6 cm, 1 kg)

Your baby has crossed the 1 kg mark. The eyes can open and close. REM sleep — the dreaming sleep — has begun, which is significant because REM sleep is essential for brain development. The baby’s brain is developing at an extraordinary rate in the third trimester.

For you: Braxton Hicks contractions — the painless practice contractions that have been occurring since the second trimester — may become more frequent and noticeable. They remain irregular and do not increase in intensity or frequency. If contractions become regular, more intense, or are accompanied by other symptoms — contact your doctor.

The third trimester monitoring begins: More frequent antenatal visits. Blood pressure monitoring is critical in the third trimester as pre-eclampsia risk is highest now.

Week 29 — Iron Stores Transfer

Baby size: Butternut squash (approximately 38.6 cm, 1.15 kg)

Your baby’s iron stores are being built up this week — the iron that will sustain them through the first six months of life, before solid food provides dietary iron. This means your iron needs are highest in the third trimester.

For you: The sheer size of the uterus is now creating physical discomfort throughout the body. Heartburn is almost universal — the uterus pushes the stomach upward, and the valve between the stomach and oesophagus is relaxed by progesterone. Small meals, avoiding lying down after eating, and sleeping slightly propped up are the most effective management strategies.

India tip: Iron supplementation is particularly important now. Take your prescribed iron supplement consistently. Pair it with amla juice or nimbu paani — vitamin C significantly increases iron absorption. Avoid chai within an hour of your iron tablet.

Week 30 — The Lungs Are Maturing

Baby size: Cabbage (approximately 39.9 cm, 1.3 kg)

The baby’s lungs are developing rapidly — producing increasing amounts of surfactant, the substance that allows the air sacs to remain open after birth. Adequate surfactant is what allows a baby to breathe independently. It is fully sufficient by approximately Week 36.

For you: Shortness of breath intensifies as the uterus continues rising toward the diaphragm. Simple activities — walking, climbing stairs — may require pauses. This is normal and will ease in the last few weeks as the baby descends (called “lightening”) and the pressure on the diaphragm reduces.

Week 31 — Rapid Brain Development

Baby size: Coconut (approximately 41.1 cm, 1.5 kg)

The baby’s brain is in its most active development period. Connections between brain cells are forming at a remarkable rate. This is the period when DHA — the omega-3 fatty acid found in fatty fish, walnuts, and flaxseeds — is most critical for fetal brain development.

For you: Sleep difficulties become significant. The bump makes every position uncomfortable. The most recommended position — left side sleeping — keeps weight off the vena cava and optimises blood flow to the placenta. A pregnancy pillow supporting the bump and positioned between the knees significantly improves comfort.

Week 32 — Practice Breathing

Baby size: Jicama/Large pear (approximately 42.4 cm, 1.7 kg)

The baby is practising breathing movements — inhaling and exhaling amniotic fluid rhythmically, exercising the diaphragm and chest muscles in preparation for breathing air after birth. The toenails are fully formed. The baby is plumping up — significant fat deposits are building under the skin.

For you: If you haven’t already, this week is ideal for starting to gather your hospital bag items. Our hospital bag checklist India guide has everything you need, organised by category.

Kick counting begins: From Week 28 onward, monitoring fetal movement is important. Most gynaecologists recommend that you should feel at least 10 movements within any 2-hour period during a time when the baby is normally active. If you notice significantly reduced movement — contact your doctor the same day.

Week 33 — The Baby’s Skull Is Hardening

Baby size: Pineapple (approximately 43.7 cm, 1.9 kg)

The baby’s skull bones are hardening — except for two areas called fontanelles (the soft spots on a newborn’s head) which remain flexible to allow the skull to compress slightly during passage through the birth canal. This compression is normal and the head reshapes within days of birth.

For you: Symphysis pubis dysfunction — pain at the pubic joint — affects many women in the third trimester as the hormone relaxin loosens the ligaments in preparation for birth. It creates a sharp, stabbing pain or ache in the pubic area, particularly with walking, climbing stairs, or turning over in bed. A physiotherapist specialising in obstetric care can help significantly.

Week 34 — Practising All the Skills

Baby size: Cantaloupe melon (approximately 45 cm, 2.1 kg)

The baby is now practising all the skills needed for life outside the uterus — sucking, swallowing, breathing, blinking, and grasping. If born now, a baby at 34 weeks has excellent survival odds with appropriate neonatal care.

For you: The final growth spurt of pregnancy is well underway — both yours and the baby’s. The physical demands of the third trimester are real: the weight of the bump affects your centre of gravity, your back, and your joints. Gentle walking, pregnancy yoga, and swimming are all helpful if you are able to continue exercise.

Antenatal class: If you haven’t attended an antenatal class — now is the time. The Lamaze technique, breathing methods for labour, what to expect during delivery, breastfeeding basics — this preparation makes a significant difference to the birth experience.

Week 35 — Getting Into Position

Baby size: Honeydew melon (approximately 46.2 cm, 2.4 kg)

Many babies move into the head-down position around this week. Your gynaecologist will begin checking the baby’s position at antenatal visits from Week 34 onward. If the baby remains breech (bottom or feet first), your gynaecologist will discuss options — which may include external cephalic version (ECV, a procedure to manually turn the baby) or planning for a caesarean section.

For you: Increased pelvic pressure as the baby descends. Frequent urination returns as the baby’s head puts pressure on the bladder. Some women experience “lightening” — a sensation of the baby dropping — which reduces pressure on the diaphragm and makes breathing easier.

Week 36 — Almost Full Term

Baby size: Papaya (approximately 47.4 cm, 2.6 kg)

The baby’s lungs are mature — surfactant production is sufficient for independent breathing. The baby is considered “early term” at Week 37. Most babies are born between Weeks 38 and 40.

For you: Your antenatal visits are now weekly or every two weeks. Group B Streptococcus (GBS) screening may be offered around this week (a vaginal swab to check for a bacteria that, if present, requires antibiotics during labour). Discuss with your gynaecologist.

Birth plan: Finalise your birth preferences — where you will deliver, who will be with you, your preferences around pain relief, episiotomy, immediate skin-to-skin contact. A written birth plan shared with your delivery team helps ensure your preferences are known.

Week 37 — Full Term

Baby size: Winter melon (approximately 48.6 cm, 2.9 kg)

Your baby is full term. They could be born at any point now — their systems are mature enough to support life outside the uterus. The remaining weeks are for further growth and the final maturation of the brain.

Signs of labour approaching:

Lightening (baby dropping into pelvis)
Mucus plug discharge — a thick plug of mucus that has sealed the cervix
Bloody show — blood-tinged mucus as the cervix begins to thin
Increased Braxton Hicks contractions
Nesting instinct — a sudden burst of energy and urge to organise

For you: The final weeks of pregnancy are often a combination of intense physical discomfort and growing anticipation. Rest as much as possible. Eat well. Let people help you. You are nearly there.

Week 38 — The Final Preparation

Baby size: Leek (approximately 49.8 cm, 3.1 kg)

The baby is shedding the vernix and lanugo — the protective coating and fine hair that covered them throughout pregnancy. The baby continues to put on approximately 30 grams of fat per day. The brain and nervous system continue their rapid development — a process that will continue for years after birth.

For you: Sleep is likely very difficult by now. Many women report waking every 1-2 hours — whether from discomfort, needing to urinate, or the baby’s activity. This disruption, as exhausting as it is, may be nature’s preparation for the frequent night waking that follows birth.

Week 39 — The Most Common Birth Week

Baby size: Watermelon (approximately 50.7 cm, 3.3 kg)

Week 39 is statistically the most common week for birth in full-term pregnancies. The baby is completely ready. Every organ system is mature. The only question is timing.

Signs of true labour vs false labour:

True Labour	False Labour (Braxton Hicks)
Contractions regular	Contractions irregular
Contractions getting stronger	Contractions stay the same
Contractions getting closer	Contractions may stop
Not relieved by movement	May improve with walking or rest
Cervix dilating	No cervical change

When to go to hospital: Contractions 5 minutes apart, lasting 1 minute each, for 1 hour (the 5-1-1 rule). Water breaking — go immediately regardless of contractions. Any bleeding. Reduced fetal movement.

Week 40 — Due Date

Baby size: Small pumpkin (approximately 51.2 cm, 3.5 kg)

The due date arrives. Approximately 80% of babies are born within two weeks of their due date — half before, half after. Only 5% of babies are born exactly on their due date.

If you reach your due date without labour: your gynaecologist will discuss options. Most practices do not intervene before Week 41. Between Weeks 41 and 42, induction of labour is typically offered because the placenta begins to age and function less effectively, and the risk to the baby increases slightly.

Post-dates monitoring: If you go past your due date, your gynaecologist will typically schedule additional fetal monitoring — non-stress tests and/or biophysical profiles to assess the baby’s wellbeing.

Essential Third Trimester Tests

Glucose Challenge / Tolerance Test (if not done in second trimester)

Gestational diabetes screening is ideally done Week 24-28 but may be repeated or done for the first time in the third trimester if missed.

Group B Streptococcus (GBS) Screening (Week 35-37)

Vaginal swab. If positive — antibiotics during labour are given. Does not affect normal delivery plans.

Fetal Growth Scan (Week 32-36)

Assesses baby’s growth, fluid levels, placental function, and position. Helps identify growth restriction or macrosomia (large baby).

Antenatal Monitoring (Ongoing)

Blood pressure at every visit — critical for pre-eclampsia detection. Urine protein. Fetal heart rate. Fundal height measurement.

Preparing for Labour — Indian Hospital Bag Essentials

For you:

Comfortable loose cotton kurtas or nightgowns (front-opening for breastfeeding)
Old comfortable underwear (you won’t want to worry about these)
Maternity pads — the heavy-duty kind (regular pads are not adequate for post-delivery bleeding)
Toiletries — soap, shampoo, toothbrush
Snacks for labour — dates, nuts, nimbu paani for energy
Documents — antenatal card, insurance, ID

For baby:

3-4 cotton jhablas or onesies
Soft cotton receiving blanket
Nappies (diapers) — small pack for hospital
Cotton cap and mittens
Baby soap, gentle baby oil

For the complete hospital bag list with India-specific recommendations, our hospital bag checklist India guide has everything organised by category.

Third Trimester Nutrition — Most Critical Needs

Iron: At its highest demand in the third trimester as fetal iron stores are built. Take your supplement consistently — with vitamin C (amla, nimbu) for maximum absorption.

DHA: The baby’s brain development peaks now. Fish for non-vegetarians (mackerel, sardines, hilsa — well cooked). Walnuts, ground flaxseeds, DHA supplement if recommended by your doctor.

Calcium: Fetal bone density is highest in the last trimester. Curd, paneer, ragi, full-fat milk, sesame seeds.

Dates: Research from Jordan and published in multiple obstetric journals suggests consuming 6 dates daily from Week 36 may reduce the need for labour induction and shorten early labour. Discuss with your gynaecologist.

Warning Signs — Go to Hospital Immediately

Any vaginal bleeding — not the mucus plug, but actual blood

Water breaking — a gush or steady trickle of clear fluid

Severe headache with visual disturbances — possible pre-eclampsia

Sudden severe swelling of face, hands, feet with headache — possible pre-eclampsia

Significantly reduced fetal movement — fewer than 10 movements in 2 hours during active period

Contractions before Week 37 that are regular and increasing — possible preterm labour

Fever above 38°C

Severe epigastric pain (upper abdominal pain) — can indicate HELLP syndrome

FAQ — Pregnancy Week by Week Third Trimester

Q: My baby is breech at Week 34. What are my options?

A baby in breech position at Week 34 has significant time to turn — many do spontaneously before Week 37. Your gynaecologist will continue monitoring the position. If the baby remains breech at Week 36-37, external cephalic version (ECV) — a procedure where a doctor manually turns the baby from outside — may be offered. If ECV is not successful or not appropriate, a planned caesarean section is typically recommended for a breech presentation.

Q: I’m past my due date. Should I agree to induction?

This is a conversation to have specifically with your gynaecologist based on your individual circumstances — your health, your baby’s monitoring results, and your preference. Most guidelines suggest induction is appropriate between Weeks 41 and 42. The decision should be made with full information about the risks and benefits in your specific situation, not as a general rule.

Q: How do I know if my water has broken?

Amniotic fluid is clear and odourless (or very faintly sweet-smelling). It comes in a gush or steady trickle and does not stop — unlike urine, which you can control. If you suspect your waters have broken, call your gynaecologist and go to hospital — regardless of whether contractions have started. Once waters break, there is a risk of infection, and most hospitals want to deliver within 24 hours.

Q: My Braxton Hicks contractions are getting more frequent. Is this labour starting?

Braxton Hicks — practice contractions — become more frequent in the final weeks of pregnancy. The key distinction from true labour: Braxton Hicks are irregular, do not increase in intensity, and often stop with movement or hydration. True labour contractions are regular, get stronger, get closer together, and do not stop. If you are unsure, call your gynaecologist — they will not mind the call.

Q: What can I do to encourage labour naturally when I’m overdue?

Walking is the most consistently recommended and safest approach — it encourages the baby to descend and may help stimulate contractions. Dates from Week 36 — the evidence suggests six dates daily may have a modest effect. Nipple stimulation can trigger oxytocin release — but should be discussed with your doctor before trying. Most other “natural induction” methods (castor oil, strong spices, evening primrose oil) either have no evidence or carry risks. Discuss any approach with your gynaecologist before trying.

Q: I’m terrified of labour. How do I manage the fear?

Fear of labour is extremely common — particularly in first-time mothers. Antenatal classes that include realistic information about what labour involves and what pain relief is available significantly reduce fear. Understanding the physiology of labour — why pain occurs and what it means — helps many women. Hypnobirthing techniques are genuinely helpful for some women. Most importantly: discuss your specific fears with your gynaecologist. Fear is not irrational and deserves to be taken seriously, not dismissed.

About This Article

Written by the MumPappaHub editorial team — including an aunt whose cousin described the third trimester as “the last month lasting approximately four years.” She delivered at Week 39. She now says the third trimester was the most important preparation she went through. She was right.

Reviewed for accuracy against WHO antenatal care guidelines and Indian Academy of Pediatrics third trimester monitoring recommendations. This content is for general informational purposes only and does not constitute medical advice. Always follow your gynaecologist’s specific guidance.

MumPappaHub — Real talk for real parents. mumpappahub.com