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Third trimester

33 weeks pregnant

At 33 weeks your baby's bones are hardening, though the skull bones stay soft to help with birth. The lungs are nearing full development but are not mature yet. Tiredness and Braxton Hicks tightenings are common, and many people start getting ready for the birth.

This page covers 33 weeks 0 days to 33 weeks 6 days (33+0 to 33+6), counted from the first day of the last period. Check how far along you are

Enter it to see the calendar dates of your week 33.

Botanical illustration of a durian

About the size of a durian

Typical estimated weight 2.16 kg (4 lb 12 oz) at 33+0, about 2.35 kg (5 lb 3 oz) by 33+6. This is the 50th centile; healthy babies commonly vary by about 12.7% either way.1

A reference value, not a measurement of your baby.

How your baby is developing

  • Your baby's bones are hardening, except the skull bones, which stay soft and flexible to help your baby pass through the birth canal.2,3
  • The lungs are nearing full development but are not fully mature yet.3,4
  • Growth and fat gain continue at a fast pace.4
  • Much of this final stretch goes into finishing growth and brain development.3
  • Your baby can see and hear many things around them and keeps processing more of what they sense.3

Changes you may notice

Everyone’s experience is different. You may notice some of these, or none.

  • Tiredness is common as you carry the extra weight.2
  • Braxton Hicks practice contractions may start or become more noticeable, feeling like a tightening for 20 to 30 seconds. They should not be painful. Call your provider or maternity unit if they become painful or regular.2
  • A heavy feeling low in the pelvis can be a sign that your baby is head down.2
  • Sleep problems, backache, heartburn, constipation, leg cramps, swelling and dizziness are common. Get medical advice about any vaginal bleeding.2
  • Keep noticing your baby's usual pattern of movements. If they slow down, stop or change, contact your provider or maternity unit immediately, even at night.5

Care around this week

  • Labor before 37 completed weeks is preterm labor. Signs include contractions every 10 minutes or more often, leaking fluid or bleeding from the vagina, pelvic pressure, a low dull backache, or period-like cramps. If you think you might be in labor before 37 weeks, contact your provider or maternity unit immediately, even in the middle of the night.6,7
  • US: the maternal RSV vaccine is given at 32 to 36 weeks during September through January in most of the country, and Tdap is recommended during weeks 27 through 36. UK: the RSV vaccine can be given up until labor, and the whooping cough vaccine, ideally given before 32 weeks, can still be given later.8,9,10
  • Group B strep is often discussed ahead of birth. US: universal screening is done at 36 weeks 0 days to 37 weeks 6 days. UK: NHS suggests asking your midwife about it, noting that up to 2 in 5 people carry it and most newborn infections are preventable.2,11

Questions to ask your provider

  • What should I pack in my hospital bag, and what does the hospital provide?
  • Who do I call if I think I am in labor before 37 weeks?
  • When will I be screened for group B strep?
  • Is there still time for my Tdap or RSV vaccine?
When to contact your provider straight away

Call 911 (US) or 999 (UK) in an emergency, such as heavy bleeding or bleeding with severe pain, a seizure, chest pain, or severe trouble breathing.12,13,14,15

These symptoms are not always serious, but each one needs prompt advice from your provider, midwife or maternity unit (or NHS 111 in the UK if you cannot reach them) rather than waiting for your next appointment, and it helps to tell them you are pregnant.

  • Vaginal bleeding or spotting at any stage of pregnancy. Call 911 or 999 if the bleeding is heavy or comes with severe belly pain, shoulder pain, or feeling faint or dizzy.14,16
  • Fluid leaking or gushing from your vagina, or discharge that is unusual for you. Get checked straight away if the fluid is greenish, colored or smells bad.7,14,15,17
  • Your baby moving less than usual, not moving, or a change in their usual pattern of movements. Call immediately, even in the middle of the night, and do not use a home Doppler to check yourself.5,14
  • A severe headache that does not go away with simple painkillers or gets worse, or sudden changes in your vision such as blurring or seeing flashing lights.12,14,15
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.12,14,15
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.12,14,18
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.17,18
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.14,15,17
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.14,15
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.19
  • Being sick so often that you cannot keep food or drink down, or signs of dehydration such as dark urine, peeing very little, or feeling dizzy.14,20
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.14,21

Questions about 33 weeks

When should I pack my hospital bag?

NHS suggests packing it around this stage, since only about 1 in 20 babies arrive on their due date. Include your notes, baby clothes, diapers, comfortable clothes, pads, toiletries, snacks and any medicines.2

Are Braxton Hicks normal at 33 weeks?

Yes. They feel like a tightening for 20 to 30 seconds and should not be painful. Call your provider or maternity unit if they become painful or regular.2

What are the signs of preterm labor at 33 weeks?

Signs include contractions every 10 minutes or more often, leaking fluid or bleeding from the vagina, pelvic pressure, a low dull backache and period-like cramps. If you think you might be in labor, contact your provider or maternity unit straight away.6,7

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. Week 33 of pregnancyNHS Best Start in Life
  3. Fetal development: stages of growthCleveland Clinic
  4. Fetal developmentUS National Library of Medicine
  5. Your baby's movementsNHS (England)
  6. Preterm laborUS National Library of Medicine
  7. Signs of going into labourNHS Best Start in Life
  8. Protecting Infants from RSVUS Centers for Disease Control and Prevention
  9. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  10. Vaccinations in pregnancyNHS (England)
  11. Committee Opinion No. 797: Prevention of Group B Streptococcal Early-Onset Disease in NewbornsAmerican College of Obstetricians and Gynecologists, 2020
  12. Pre-eclampsiaNHS (England)
  13. Epilepsy and pregnancyNHS (England)
  14. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  15. Pregnancy symptoms you need to get help forNHS (England)
  16. Vaginal bleeding in pregnancyNHS (England)
  17. Premature labour and birthNHS (England)
  18. Stomach pain in pregnancyNHS (England)
  19. Itching in pregnancyNHS (England)
  20. Severe vomiting in pregnancyNHS (England)
  21. Depression in pregnancyNHS (England)

Links checked November 12, 2026. Citing a source does not mean it endorses this site.

Written from the sources above and checked against them on 2026-11-12. Not reviewed by a clinician. Our editorial policy