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Trimester 3 · Week 33 of 40

Week 33 of pregnancy: Listening and Learning

Skull bones stay soft for birth while weight gain nears its peak. Easing back pain and broken sleep, flying late in pregnancy, and preparing to breastfeed.

Last updated 28 September 2026

What's happening this week?

At 33 weeks your baby is filling out quickly and the bones are firming up, although the skull deliberately stays flexible. For you, a heavier bump often brings back or buttock pain and nights that are hard to settle. It is a good week to decide whether any travel is really needed before the final weeks, and to start learning how breastfeeding works. Keep noticing your baby's usual pattern of movements every day.

Baby's development

Your baby's skeleton continues to harden, but the bones of the skull are not fused. They stay as separate plates so the head can change shape slightly, or mould, as it passes through the birth canal.

In the last trimester babies typically gain about 150–220 g a week, and the fastest rate is usually reached around 35 weeks. Much of this gain is fat, which rounds out the body and will help your baby keep warm after birth. Brown fat, a special heat-producing type, has been building since roughly 26–30 weeks.

Antibodies called IgG pass from your bloodstream across the placenta in increasing amounts during the third trimester, giving your baby some protection against infection in the early weeks after birth.

Since about 27–28 weeks nearly all babies respond to sound, so a loud noise may startle yours and familiar voices may be picked up. Periods of quiet and activity alternate, though fully organised sleep and wake states do not appear until around 36 weeks. The lungs are still maturing: surfactant, which keeps the tiny air sacs open, is usually mature at about 34–36 weeks, which is why babies born now often need neonatal care.

Your baby's size

About the size of a cantaloupe

43.7 cm

17.2 in · Length

1900 g

Weight

Week 33

Gestational age

The 43.7 cm and 1.9 kg shown are a typical crown-to-heel length and estimated weight, not targets. Scan weight estimates have a wide margin, and a healthy baby this week might weigh roughly 1.9–2.4 kg. Indian babies often track a little below Western charts, and the cantaloupe is only a rough picture.

Your body this week

Your blood volume is around its peak now, roughly 40–50% more than before pregnancy, and your heart is working harder to move it. The uterus sits high under the ribs, so breathlessness when climbing stairs is common, and heartburn can flare after a large meal.

The extra weight at the front changes your posture and strains the lower back. For some people the pain spreads into a buttock or down the back of a leg, often called sciatica. Pregnancy hormones loosen ligaments, adding to the ache. Pain over the pubic bone, or when parting your legs, may be pelvic girdle pain instead, which a physiotherapist can help with.

Sleep often becomes fragmented: a full bladder, heartburn, cramps, a busy baby and a mind running ahead to the birth can all wake you. Your breasts have been making colostrum since mid-pregnancy, and some people notice small drops or dried crusts on the nipples. Others never leak before birth, and both are normal.

Symptoms you may notice

Every pregnancy is different - you may have some, all or none of these.

Back pain or sciatica: Posture changes and loosened ligaments strain the lower back. Sit with your back supported and bend your knees to lift. Paracetamol is generally the preferred painkiller if needed; avoid ibuprofen and similar medicines unless a doctor advises. Backache that comes and goes in waves before 37 weeks needs checking.
Trouble sleeping: Several things wake you at once in late pregnancy. Settle on your side with a pillow between your knees, keep the room cool, and if you wake on your back, simply turn over.
Breathlessness: The uterus presses up on your diaphragm. Slow down and sit upright. Sudden breathlessness, breathlessness at rest or with chest pain is an emergency.
Heartburn: Smaller meals and not lying down straight after eating help. Raising the head end of your bed can ease night-time symptoms.
Leaking colostrum: Small leaks are normal, and so is no leakage at all. A breast pad or folded soft cloth inside your bra keeps clothes dry.

Medical care and tests

Third antenatal visit (India)
Routine
28 to 34 weeks
India's minimum schedule includes a visit in this window, ideally with a medical officer. Blood pressure, weight, urine, haemoglobin and bump size are checked. Raised blood pressure or protein in the urine can lead to closer monitoring for pre-eclampsia, and low haemoglobin to a change in iron treatment.
Second Td dose, if still due
Only if needed
4 weeks after the first dose
If your first Td injection was given late, older Indian guidance prefers the second dose at least a month before the due date. If you had two doses in a pregnancy within the last three years, one booster is usually enough. Check your MCP card or ask your ANM.
Whooping cough and RSV vaccines
Varies by provider
Tdap 27 to 36 weeks; RSV 32 to 36 weeks (US)
In India, FOGSI recommends Tdap in place of the second Td dose at 27–36 weeks, mainly offered in private practice. The US gives an RSV vaccine at 32–36 weeks in season and the UK from 28 weeks; it is reportedly not available for pregnant women in India.

Schedules differ between government and private care and between countries. Free check-ups are available at government facilities on the 9th of each month under PMSMA; follow the plan on your own card.

Nutrition this week

Aim for an earlier, lighter dinner. Dal with rice or roti and a cooked sabzi, or vegetable khichdi with dahi, sits more easily than fried or rich food. ICMR-NIN advises not sleeping immediately after a meal, which also helps heartburn.
Spread your fluids through the day; ICMR-NIN suggests more than 2 litres daily. Drinking less close to bedtime may reduce night-time toilet trips for some people.
Have tea or coffee earlier in the day and keep total caffeine under 200 mg; a 150 ml cup of tea has roughly 30–65 mg.
If hunger wakes you, warm milk, a banana or roasted makhana is fine. Keep taking your iron and calcium tablets as prescribed, at different times of day.

Movement and exercise

Walking, swimming and prenatal yoga remain good choices, as long as you can still talk comfortably while moving.
For back and buttock pain, try gentle pelvic tilts on hands and knees, and avoid standing still for long spells. A physiotherapist can suggest exercises if pain limits your walking.
Limit time lying flat on your back; do floor exercises side-lying or propped up. Stop if you feel dizzy, notice fluid leaking or bleeding, or get painful tightenings.

Things to keep in mind

Flying: RCOG advises avoiding flights from 37 weeks with one baby, and from 32 weeks with twins or preterm risk factors. Airline rules vary and many need a fit-to-fly letter late in pregnancy, so check before booking and carry your records.
On any long trip, walk about regularly, drink water, and wear the lap belt under your bump.
Learn how to hold your baby and what a good latch looks like, ideally with your partner or a family member, because family support matters. Do not express colostrum unless your maternity team suggests it.

When to contact your doctor

Call your doctor or midwife the same day if you have

Itching of the palms or soles, especially if it is worse at night.
Any vaginal bleeding, even light spotting.
A temperature of 38°C or above, or burning when you pass urine.
Pain, warmth or swelling in one calf.
New swelling of the face or hands, or a headache that will not settle.
Low mood or anxiety most days for two weeks or more.

Get emergency care now if you have

Your baby's movements slow down, change or stop.
Regular tightenings, fluid leaking or a show before 37 weeks.
Heavy bleeding or severe, constant abdominal pain.
Severe headache with blurred vision or pain under the right ribs.
Chest pain or sudden breathlessness.

In India, call 108 for an ambulance, 102 for free transport for pregnant women in many states, or 112 for any emergency - or go straight to your nearest hospital with a maternity unit.

If something feels wrong, trust that feeling and call - you never need to wait for your next appointment.

Questions to ask your doctor

Is my back pain sciatica or pelvic girdle pain, and would physiotherapy help?
Is it safe for me to travel in the next few weeks?
Is my Td schedule complete, and do you recommend Tdap?
Is there a breastfeeding class or counsellor here?

Week 33 checklist

Check your MCP card for completed Td doses
Confirm any travel plans against airline rules
Set up pillows for side-sleeping
Join a breastfeeding class or watch a positioning session
Save the labour ward's contact number

Frequently asked questions

Can I fly at 33 weeks?

Air travel is not harmful in itself in an uncomplicated pregnancy. RCOG advises avoiding it from 37 weeks with one baby, or from 32 weeks with twins or preterm risk factors. Airlines set their own limits and many want a fit-to-fly letter, so check before booking and talk to your doctor first.

Is sciatica in pregnancy harmful to the baby?

Back and buttock pain is uncomfortable but does not harm your baby. Posture changes, loosened ligaments and the weight of the bump are the usual causes. Side-sleeping with a pillow between your knees, good back support and gentle exercise can help. Pain that comes in regular waves may be labour and should be checked.

Should I express breast milk before my baby is born?

Not unless your maternity team suggests it. Some units teach hand-expressing colostrum from about 36–37 weeks, particularly for mothers with diabetes, and show you how. For most people, the useful preparation now is learning about positioning and latch so feeding starts more smoothly.

This page is general information, not a diagnosis or a substitute for care from your own doctor or midwife. Pregnancies differ, and timings here are typical ranges rather than deadlines. Read our medical disclaimer and editorial policy.