Third Trimester Guide: What to Expect in the Final Stretch

The third trimester begins at week 28 and runs through to birth, which for most women is somewhere between weeks 39 and 41. These final twelve or so weeks bring the most significant physical demands of pregnancy — the largest bump, the most disrupted sleep, the most appointments, and the most preparation to do before your baby arrives.

They also bring the clearest sense of the finish line, which matters when the physical discomfort is real and relentless. Understanding what to expect makes it considerably easier to navigate — not because knowing changes what happens, but because recognising what's normal removes the anxiety that compounds everything else.

What's happening in your body in weeks 28 to 40

Your baby's growth accelerates

Your baby grows from around one kilogram at 28 weeks to an average of 3.4 kilograms at birth, gaining the majority of their body weight in the final trimester. This rapid growth drives most of the physical changes you'll notice — the increasing size and weight of the bump, the shortness of breath as your uterus pushes against your diaphragm, and the frequency of urination as your bladder has progressively less room.

By week 36, most babies settle into a head-down position in preparation for birth. Your midwife or obstetrician will check your baby's position at appointments in the final weeks. If your baby is in a breech position at 36 weeks, your care team will discuss options with you including external cephalic version, a procedure that can turn a breech baby, and what a breech presentation means for your birth options.

Braxton Hicks become more noticeable

Practice contractions become more frequent and often more noticeable in the third trimester. They feel like a tightening across the abdomen, usually painless, and unlike true labour contractions they don't become progressively stronger, longer, or closer together. Staying hydrated and changing position usually eases them. If contractions become regular, painful, or you have any other concerns including reduced fetal movement, contact your midwife promptly.

Shortness of breath

As your uterus expands upward, it reduces the space available for your lungs to expand fully. Feeling breathless during mild exertion is common from around 28 to 32 weeks. For many women this eases slightly in the final few weeks when the baby drops lower into the pelvis — a process called engagement or lightening — though this is more common in first pregnancies than subsequent ones. Sudden or severe breathlessness at any point warrants prompt medical assessment.

Swelling

Mild swelling of the feet and ankles, called oedema, is common in the third trimester and is caused by the increased blood volume and fluid retention of late pregnancy combined with the pressure your uterus puts on the blood vessels returning blood from your legs. It typically worsens over the course of the day and improves overnight with your legs elevated.

Swelling that is sudden, severe, or involves your face or hands warrants immediate medical attention as it can be a sign of pre-eclampsia. Similarly, swelling in one leg that is significantly worse than the other — particularly with redness, warmth, or pain — should be assessed promptly to rule out deep vein thrombosis.

Pelvic pressure and lightning crotch

As your baby grows and their head engages lower into your pelvis, many women experience a sharp, shooting pain through the pelvis or vagina — colloquially called lightning crotch. It is caused by your baby's position putting pressure on pelvic nerves and is completely normal, if startling. It passes within seconds and is not a sign of labour starting.

General pelvic heaviness and pressure in the lower abdomen is also common from around 32 weeks as the baby's weight bears down on the pelvic floor. Pelvic floor exercises, supportive underwear, and reducing time on your feet all help manage this.

Sleep in the third trimester

Sleep in the third trimester is genuinely hard for most women. The combination of a large bump limiting comfortable positions, hip and pelvic pain from side lying, frequent bathroom trips, heartburn, Braxton Hicks, fetal movement, and a busy mind adds up to fragmented, unrestorative sleep that affects mood, energy, and pain tolerance in a cycle that feeds itself.

From 28 weeks, NSW Health recommends settling to sleep on your side for every sleep — nights, naps, and returning to sleep after waking. Either left or right side is fine. If you wake on your back, simply roll back onto your side. The focus is on the position you fall asleep in.

Making side sleeping sustainable through the third trimester requires addressing three zones simultaneously: support under your bump to reduce the downward pull on your lower back, support between your knees to keep your hips stacked rather than letting the top hip drop forward, and something behind your lower back to discourage rolling. A setup that maintains all three through a night of movement makes a measurable difference to the frequency of overnight waking from pain.

The Bumpnest Maternity Pillow is designed specifically for this stage — the three-component modular system addresses each zone independently so the support stays in place when you roll, without the bulk of a full-body pillow. If sleep disruption is significantly affecting your daily function, this is the stage where getting your setup right makes the most difference.

For everything else affecting third trimester sleep — heartburn, restless legs, temperature regulation — our [third trimester sleep survival guide] covers practical management strategies in detail.

Your antenatal appointments in the third trimester

Appointments become more frequent in the third trimester. For uncomplicated pregnancies, you'll typically see your midwife or obstetrician every two to four weeks from 28 weeks, increasing to every one to two weeks from 36 weeks.

Each appointment covers blood pressure and urine testing, fundal height measurement to track your baby's growth, and checking your baby's heartbeat. Your baby's position is checked from around 34 to 36 weeks.

Key appointments and tests in the third trimester include:

At around 28 weeks, most women have a glucose tolerance test to screen for gestational diabetes if not already completed. A blood test also checks iron levels, rhesus antibodies for rhesus-negative women, and other routine markers. A whooping cough vaccination is recommended between 28 and 32 weeks of every pregnancy — it protects your newborn before they're old enough to be vaccinated themselves.

At around 35 to 37 weeks, a Group B Streptococcus swab may be offered. GBS is a bacteria carried by around 25 percent of women without causing any symptoms, but it can cause serious infection in newborns if transmitted during birth. A positive result means antibiotics will be offered during labour rather than requiring a caesarean.

Your care team will also discuss your birth preferences, what to expect in early labour, and when to contact them or go to hospital. If you haven't completed antenatal education, the third trimester is the time to do it — classes fill quickly and the information is most useful when birth is approaching rather than months away.

Preparing practically in the third trimester

Pack your hospital bag by 36 weeks. Preterm labour and unexpected early admissions do happen. Having your bag ready before 36 weeks means one less thing to manage if things progress faster than expected. Our [what to pack in your hospital bag] guide covers everything you need in detail.

Write your birth preferences. A birth preferences document is not a rigid plan — birth is unpredictable. It's a clear, concise outline of your preferences around pain relief, monitoring, delayed cord clamping, skin-to-skin contact, and anything else that matters to you, so your care team can refer to it without you needing to communicate everything mid-labour.

Prepare your home for the postpartum period. Stock the freezer with meals. Set up a feeding station with water, snacks, phone charger, and whatever you'll need within arm's reach during night feeds. Buy more maternity pads than you think you'll need. Have a plan for who will help in the first two weeks. These are the practical preparations that make the biggest difference to how the postpartum period starts.

Install the car capsule. Your baby cannot leave the hospital without a properly installed rear-facing capsule. Many councils, NRMA locations, and baby retailers offer free installation checks. Book one before your due date.

Emotional changes in the third trimester

The third trimester brings a particular emotional landscape that is worth acknowledging. The excitement of approaching birth coexists with anxiety about labour, about parenthood, about how everything will change. The physical discomfort makes it harder to manage emotions that would be manageable with adequate sleep and energy. And the reality of the impending transition — to parenthood, to a completely different life — tends to crystallise in these final weeks in ways that earlier in pregnancy it didn't.

Nesting instincts — a compulsion to organise, clean, and prepare the home — are common and can be useful when channelled into practical preparation. They can also become counterproductive if they drive exhaustion in a period when rest matters.

Antenatal anxiety is extremely common and very treatable. If anxiety about birth, parenthood, or your baby's health feels persistent, intrusive, or overwhelming, speak with your GP or midwife. This is not something to manage alone and it does not need to reach crisis level before it's worth addressing.

Monitoring your baby's movements

From 28 weeks, awareness of your baby's movement pattern becomes important. There is no defined number of movements that is normal — what matters is that you know your baby's individual pattern and notice if it changes.

If you notice a significant reduction in your baby's movements compared to their usual pattern, or if movements stop, contact your midwife or maternity assessment unit promptly. Do not wait until the next day and do not be reassured by drinking cold water or lying on your left side — these are myths. Your care team would always rather assess and reassure you than have you wait at home with reduced movements.

The Safer Baby Bundle at stillbirthcre.org.au has clear, evidence-based information on monitoring fetal movement that is worth reading and bookmarking.

When to contact your midwife or go to hospital

Contact your midwife or maternity assessment unit promptly if you experience reduced or absent fetal movement, regular contractions before 37 weeks, sudden or severe swelling particularly of the face or hands, a severe headache particularly with visual disturbances, vaginal bleeding at any point, your waters breaking, or any symptom that feels urgent or wrong to you.