By the time the third trimester begins at week 28, you have already come a long way. The first trimester’s exhaustion and nausea are (mostly) behind you. The second trimester’s relative ease and first movements are giving way to something new: the unmistakable physical reality of a baby who is running out of room, a body that is preparing for one of the most significant physical events of your life, and an anticipation that is somewhere between excitement and something that is harder to name. The third trimester is not always comfortable. But it is purposeful — every week brings your baby closer to readiness for the world outside. This guide covers what to expect, what to prepare, and how to navigate the final stretch.

Your Baby’s Development in Weeks 28–40

The third trimester is defined primarily by growth. Your baby goes from around 1kg at week 28 to approximately 3–3.5kg at full term, with the majority of that weight gain happening in the final eight weeks. This is not merely mass — it is the fat stores your baby will use for temperature regulation after birth, the lung maturation needed for independent breathing, and the neurological development that continues at a remarkable pace right through to and beyond birth.

Key developmental milestones by week

• Week 28: The eyes open for the first time. Rapid brain development is underway. The baby can hiccup — which you may feel as rhythmic, regular jolts.
• Week 32: Bones are fully formed, though the skull remains soft and flexible to allow passage through the birth canal. Most babies have settled into a head-down position by this point, though some turn later.
• Week 34: The lungs are maturing; a baby born at this point would likely need respiratory support but would survive with specialist care. Fat continues to be deposited under the skin.
• Week 36: The baby is considered “”late preterm”” — most major development is complete, but the final weeks of growth and maturation matter. Lanugo (fine body hair) begins to disappear.
• Week 37–40: Full term. The baby continues gaining weight and the lungs fully mature. The baby’s head may “”engage”” in the pelvis — called lightening — which can make breathing slightly easier while increasing pelvic pressure.

What Your Body Is Doing in the Third Trimester

The physical experience of the third trimester is shaped largely by the sheer size of the bump and by the body’s preparation for birth. Many of the symptoms of these weeks are uncomfortable but purposeful.

Braxton Hicks contractions

Braxton Hicks — irregular, usually painless tightening sensations across the abdomen — are the uterus practising the contractions of labour. They are common from the second trimester but become more noticeable in the third. They differ from labour contractions in that they are irregular, do not increase in intensity over time, and typically ease with rest or a change of position. If you are unsure whether contractions are Braxton Hicks or early labour, your midwife team can advise.

Sleep disruption

Sleep in the third trimester becomes progressively more difficult — a combination of physical discomfort, frequent urination, and the difficulty of finding a comfortable position. Side-sleeping is recommended from 28 weeks; a pregnancy pillow between the knees and under the bump can significantly improve comfort. If you wake on your back, simply roll to your side — there is no need for alarm about the time spent there.

Pelvic girdle pain

Pelvic girdle pain (PGP) — pain in the pelvis, hips, and sometimes the lower back — affects a significant proportion of pregnant people in the third trimester, caused by the hormone relaxin loosening the ligaments of the pelvis. It ranges from mild to severe. If PGP is affecting your daily functioning, tell your midwife — referral to a physiotherapist who specialises in pregnancy can make a substantial difference.

Heartburn and breathlessness

As the uterus pushes upward against the stomach and diaphragm, heartburn and breathlessness often increase. Smaller, more frequent meals, avoiding lying flat after eating, and sleeping slightly propped up can help with heartburn. Breathlessness typically improves in the final weeks when the baby’s head engages and the uterus drops slightly.

Preparing for Birth in the Third Trimester

The third trimester is the practical preparation phase — the point at which thinking about birth transitions into preparing for it. The decisions and preparations of these weeks do not need to be all-or-nothing; they can be approached one by one.

Birth preferences

A birth plan — more accurately called a birth preferences document — is a record of what matters to you about your birth experience: your preferences for pain relief, who you want present, how you feel about interventions, and what you would want to happen in various circumstances. It is not a contract, and birth rarely follows a plan precisely. Its value is in the conversations it generates with your care team, and in ensuring you have thought through your options before you are in labour. Your midwife can help you develop it.

Antenatal classes

Antenatal classes — whether NHS-provided, NCT, or independent — offer practical information about labour, birth, and the early postnatal period, alongside the opportunity to meet other parents at a similar stage. They are not obligatory, but many parents find them genuinely useful for both information and connection. Book early, as popular classes fill up.

The hospital bag

Most parents pack their hospital bag from around week 36. Standard items include: your maternity notes and birth preferences, comfortable clothing for labour and the postnatal period, toiletries, snacks, a phone charger, and a going-home outfit for the baby — including an appropriate car seat if you are travelling home by car.

“”The third trimester is where pregnancy stops being something happening to you and starts being something you are preparing for. The parents who feel most ready are not those who have planned for every outcome — they are those who trust that they can handle what comes.””

— Jenny Smith, NHS consultant midwife and author of The Midwife’s Handbook. Smith has supported thousands of families through the transition to birth and the immediate postnatal period. Her observation about the nature of birth readiness — rooted in trust rather than control — is a perspective that consistently helps parents approach the third trimester with less anxiety and more groundedness.

For a complete overview of your pregnancy from week one to birth, including first and second trimester guidance, visit our full Pregnancy Week by Week guide in the Pregnancy section.

Frequently Asked Questions

How do I know if I am in labour?

Labour typically begins with one or more of: regular contractions that increase in intensity and frequency over time and do not ease with rest; a “”show”” (a mucus plug, sometimes blood-tinged, from the cervix); or rupture of membranes (waters breaking — which may be a gush or a slow trickle). Your midwife will have given you guidance on when to contact the labour ward based on your individual circumstances. When in doubt, call your midwife team — they are there to help you make the right call.

What is the difference between Braxton Hicks and real contractions?

Braxton Hicks are irregular, usually painless, do not increase in intensity over time, and tend to ease with rest or movement. Labour contractions are regular, become progressively stronger and longer, come at decreasing intervals, and do not ease with rest. If you are timing contractions and finding they are regular and increasing, contact your midwife team.

Should I be worried if my baby moves less?

A change in your baby’s usual movement pattern in the third trimester — specifically, a reduction from what is normal for your baby — should always be reported to your midwife or maternity unit. Do not wait until the next day, and do not rely on the idea that movement reduces near the end of pregnancy (it should not). Movement monitoring apps and counting kicks campaigns (such as Count the Kicks) provide useful practical guidance.

My baby is in a breech position at 34 weeks — should I be worried?

At 34 weeks, around 20% of babies are still in a breech (bottom-down) position. The majority turn spontaneously before 36–37 weeks. If your baby remains breech at 36 weeks, your care team will discuss your options — including external cephalic version (ECV), a procedure to manually turn the baby — and your birth choices. Most breech presentations are manageable; the conversation with your midwife or obstetrician at that point will clarify your specific situation.

How will I know if I am overdue and what happens then?

If you have not gone into labour by your due date, you are not yet “”overdue”” in a clinical sense — full term is considered 37–42 weeks. At 41 weeks, most care providers offer a membrane sweep (a procedure to encourage labour) and discuss induction. By 42 weeks, induction is typically recommended. Your care team will explain the monitoring and decision-making process clearly; you have the right to discuss all options and to make informed decisions about your care.

Key Takeaways

• The third trimester (weeks 28–40+) is primarily about rapid growth — your baby gains most of their birth weight and completes lung maturation in these final weeks.
• Braxton Hicks contractions, sleep disruption, heartburn, and pelvic girdle pain are common and purposeful — most are manageable with simple adjustments.
• Birth preparation in the third trimester includes developing birth preferences, considering antenatal classes, and packing a hospital bag from around week 36.
• A change in your baby’s movement pattern should always be reported to your midwife or maternity unit — do not wait.
• Labour typically announces itself through regular, increasing contractions, a show, or waters breaking — when in doubt, call your midwife team.
• Most babies who are breech at 34 weeks turn before 37 weeks; your care team will discuss options if this does not happen.

The third trimester is the final chapter of a story that has been building for seven months. It is physically demanding, emotionally complex, and — for almost every parent — profoundly meaningful. The discomfort is real, and so is everything else. Whatever happens in the weeks ahead, you are more prepared than you feel. Trust the process, trust your care team, and trust yourself. You are nearly there.