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Pregnancy Guide·Third Trimester

Week 33: Immune Antibodies Transferring

Pineapple (~29cm crown-rump)·Last reviewed: 25 April 2026
Quick answer

At week 33, antibodies are being transferred from you to your baby through the placenta, building their immune system. According to Nuhah's pregnancy guide, your baby weighs about 1.9kg and their bones are continuing to harden.

Baby development at week 33

Antibodies are being actively transferred from you to your baby through the placenta, providing passive immunity for the first few months after birth. Bones continue to harden, though the skull remains soft for birth. The baby weighs about 1.9kg and is roughly 44cm from head to toe. The pupils can now constrict and dilate in response to light.

Your body this week

You may feel very heavy and tired. Walking may be uncomfortable due to pelvic pressure. Heartburn can be intense. Sleeping on your side with a pillow between your knees may help with comfort. Some people experience restless legs or leg cramps at night. Mood swings can return as hormones shift.

Things to do this week

1
Finalise your birth plan and share it with your midwife and birth partner
2
Make sure your hospital bag is packed
3
Prepare frozen meals for after the birth
4
Discuss the whooping cough vaccination with your midwife (usually offered at around 20 weeks)

Frequently asked questions

What vaccines are recommended during pregnancy?

The whooping cough (pertussis) vaccine is recommended for all pregnant people, ideally from around 20 weeks (optimal window 20-32 weeks), but it can be given later. It protects your baby in their first weeks of life before they receive their own vaccinations. The flu vaccine is also recommended during pregnancy.

Related reading

Preparation
Hospital Bag Checklist: What to Actually Pack

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