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33 Weeks Pregnant: Baby Size, Symptoms and What to Do

Week 33 is in the third trimester, month 8 of pregnancy. Here's how big your baby is, what's developing, what you may feel and what to do this week.

Week 33 · 3rd trimester · month 8
About the size of a cantaloupe
about 17.3 in (44 cm) · 4.6 lb (2,100 g) (head to heel)

Your baby this week

Your baby's nervous system is fully developed and the bones are hardening. The skull bones stay soft and unfused so the head can pass through the birth canal more easily.

At 33 weeks your baby is receiving antibodies from you through the placenta, which help protect against infections in the first months; this is also how vaccines given in pregnancy reach your baby. The skull bones aren't fused yet, so the head can pass through the birth canal. Your baby alternates between sleeping and waking, and the pupils now narrow in bright light. For you, pelvic and pubic bone pain is common because hormones loosen the joints. Taking smaller steps, keeping your knees together when getting up and avoiding standing on one leg can help. If pain makes walking hard, ask about a referral to a physical therapist.

By the numbers

Week 33 covers days 231 to 237 counted from the first day of your last period, which is 83% of a 40-week pregnancy. About 49 days remain until a 40-week due date. Since last week, an average baby gains about 7.1 oz (200 g). By date of conception, your baby is about 31 weeks old.

Pregnancy is dated from the first day of your last period, so conception happens around week 2. Your due date is 280 days (40 weeks) from that day, and an early ultrasound may adjust it.

Your body

Pelvic aches and trouble getting comfortable at night are common. Call if pelvic pain is severe or comes with regular tightening of your belly.

Tests and to-dos this week

Install the car seat and have it checked. Ask your provider which signs mean it's time to call or head to the hospital.

  • Tdap (whooping cough) vaccine · weeks 27–36 · vaccine

    Recommended during each pregnancy, preferably early in this window.

  • RSV vaccine (September–January) · weeks 32–36 · vaccine

    Or your baby can get an RSV antibody shot after birth instead; ask your provider which option fits.

Coming up: Group B strep (GBS) test (from week 36). Full prenatal visit schedule

Tips for the third trimester

  • From 28 weeks, go to sleep on your side; if you wake on your back, just roll over.
  • Pack your hospital bag and agree with your provider on when to head in.
  • Call right away, even at night, if your baby moves less or differently.
  • Know the signs of labor: regular, strengthening contractions, your water breaking or a bloody show.

Call your provider or labor and delivery right away if you have:

  • your baby is moving less or differently than usual
  • your water breaks, especially if the fluid is green, brown or smells bad
  • bright red bleeding or constant, severe belly pain
  • a severe headache, vision changes, pain under the ribs or sudden swelling
  • intense itching, especially on the palms and soles

In an emergency, call 911.

Last week and next week

Last week (32): Your baby is fully formed and mostly gaining weight now.

Next week (34): Space is getting tight, so your baby stays curled up.

Frequently asked questions

How big is the baby at 33 weeks?

About the size of a cantaloupe: about 17.3 in (44 cm) · 4.6 lb (2,100 g), measured head to heel. These are rounded averages, and every baby grows at their own pace.

How many months is 33 weeks pregnant?

33 weeks is in month 8 and the third trimester. About 7 weeks (49 days) remain until a 40-week due date. Months are approximate; providers count weeks and days.

Why does my pubic bone hurt in pregnancy?

Pregnancy hormones loosen the pelvic joints, which can cause pain known as pelvic girdle pain or symphysis pubis dysfunction. Physical therapy, gentle movement and a support belt can help; tell your provider if pain is severe.

What's the next test or appointment after week 33?

Next up: Group B strep (GBS) test, from week 36. Your provider may schedule things differently depending on your health and local practice.

Sources

Last reviewed: November 14, 2026 · Kitpebble editorial team

This page is for general information. It isn't medical advice or a diagnosis and doesn't replace your OB-GYN or midwife. Sizes are rounded averages. Our editorial policy

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