At 33 weeks your baby is about 42.5 cm and 1.9 kg — roughly a pineapple — with a genuine sleep-wake schedule now and bones strengthening throughout the body, except deliberately at the skull.
The short answer: sleep and wake periods are now clearly distinct — eyes closed during sleep, actively looking around when awake. Bones are strengthening everywhere except the skull, which stays soft and moveable on purpose to help with birth. For you, amniotic fluid is gradually decreasing as baby fills the available space, movements can feel sharp enough to be uncomfortable, and heartburn often worsens.
Your baby this week
Baby's sleep and wake periods are now genuinely distinct — eyes closed during sleep phases, actively looking around during waking ones, a real behavioural rhythm rather than just a slowdown in movement. Bones throughout the body are getting stronger and denser, with one deliberate exception: the skull bones stay soft and separated by flexible sutures, allowing the skull to overlap slightly and mould as it passes through the birth canal.
Weight is now around 1.9 kg, and the pace of weight gain continues to be substantial from here through the final weeks.
Your body this week
Baby now occupies nearly all the available space, so amniotic fluid levels begin gradually decreasing from here — a normal, expected part of the trajectory rather than something to track. Movements can be felt very sharply now, sometimes enough to make you wince if an elbow presses into your ribs at just the wrong angle — a real change from the softer rolls of earlier months.
Heartburn often worsens around now, and avoiding lying down right after eating helps more than most other single change. If your partner is planning to support you through labour, this is also a good time for a refresher on massage, breathing cues, and other practical ways to help once things start.
Swelling in the feet and ankles tends to be more noticeable by now too, especially after standing for long stretches or by the end of a warm day. Elevating your feet, wearing supportive footwear, and staying hydrated all genuinely help — a comfortable shoe that fit fine at 20 weeks may no longer fit the same way, and that is completely normal.
Tests and appointments
Most care pathways have nothing specific scheduled precisely at 33 weeks, though appointments continue at their now-frequent pace through the rest of the third trimester.
✅ Worth doing this week
- Keep counting kicks daily — 10 movements in 2 hours remains the standard to check against
- Avoid lying down right after meals to ease worsening heartburn
- Talk through the birth plan with your partner if you have not already
- Shift position when a jab feels sharp — it often eases quickly
- Refresh labour support techniques together if your partner will be with you
When to call your doctor
Call the same day if: movement feels reduced or different from baby's usual pattern, especially fewer than 10 movements in 2 hours during an active period. Also call for bleeding, severe or one-sided abdominal pain, a severe headache with visual disturbance, sudden swelling of the face or hands, or a temperature above 38°C.
FAQ — 33 weeks pregnant
Why does the baby have closed eyes during sleep now?
By 33 weeks, sleep and wake periods are distinct enough that the difference actually shows: the eyes stay closed during sleep phases and open during active, awake periods, much like a newborn's pattern after birth. This is a real behavioural cycle, not just movement slowing down.
Why do skull bones stay soft this late in pregnancy?
Unlike most of the skeleton, which is hardening rapidly by now, the skull bones are deliberately kept soft and separated by flexible joints called sutures. This lets the skull overlap slightly and mould as it passes through the birth canal during vaginal birth, then gradually fuses over the first couple of years of life.
Why do movements suddenly feel sharp and even painful?
With baby taking up nearly all the available space now, an elbow or foot pressing into the ribs or a nerve can genuinely be felt sharply, sometimes enough to make you wince — a real change from the softer rolls of earlier months, not a sign that anything is wrong. Shifting position often helps if a particular jab becomes uncomfortable.
How big is the baby at 33 weeks?
About 42.5 cm and 1.9 kg — roughly a pineapple. Bones are strengthening throughout the body, with the deliberate exception of the skull, which stays soft and moveable to ease the passage through the birth canal.
Week 33 at a glance
At 33 weeks your baby is about 42.5 cm and 1.9 kg, with a genuine sleep-wake schedule and bones strengthening everywhere except the skull, which stays deliberately soft for birth. For you, amniotic fluid gradually decreases as baby fills the available space, movements can feel sharply distinct, and heartburn often worsens — all typical of this stage of the third trimester.
Inside Baby Novum: the birth plan template helps you set down preferences for pain relief, support people, and the first hour after birth, so the conversation with your care team starts from something written down.