At 33 weeks pregnant, your baby is about the size of a pineapple, and bones are hardening throughout the body — except for the skull, which stays soft and flexible on purpose. Seven weeks (give or take) to go, and the body is quietly getting ready for delivery in some very specific ways.

If your dates feel confusing, remember that gestational age counts from the first day of your last period (LMP), not from conception — so "33 weeks pregnant" usually means about 31 weeks since ovulation. For the full timeline, see our pregnancy week-by-week guide, or find out exactly how your due date is calculated. If you're picking up from last week, catch up on 32 weeks pregnant first.

Diagram comparing a pineapple to a 33 week fetus, showing bones hardening except the still-soft skull — At 33 weeks, your baby is about the size of a pineapple, with bones hardening except the still-soft skull.

Key takeaways

Baby is about the size of a pineapple (roughly 43.7 cm, head to heel) and weighs around 1,918 grams.
Bones are hardening throughout the body, but the skull stays soft and flexible for delivery.
About 7 weeks remain until a typical full-term due date.

What "33 Weeks Pregnant" Actually Means

Using standard gestational dating, week 33 starts about 31 weeks after ovulation, placing you well into the third trimester. In fetal-age terms (counting from conception rather than your last period), this is closer to "31 weeks post-conception."

With roughly 7 weeks left until a typical 40-week due date, many providers are now seeing patients every two weeks and starting to talk through birth plan details in more depth.

Baby Size at 33 Weeks

At 33 weeks, your baby is about the size of a pineapple — roughly 43.7 centimeters long, measured head to heel, and weighing around 1,918 grams. (Source: Baby Your Baby, Utah Department of Health)

Bones Hardening, Except the Skull

This week, your baby's bones are hardening throughout the body — with one deliberate exception. The cranial bones around the brain stay soft and somewhat flexible, since they need to be able to shift and overlap slightly to help your baby's head descend through the birth canal during delivery. (Source: Cleveland Clinic)

Those same soft skull bones are also why newborns have the soft spots (fontanelles) parents are often told to be gentle around — they typically firm up and close over the following months and years as the skull knits together after birth.

Diagram showing a 33 week fetus skeleton hardening while the skull bones stay soft and flexible — By 33 weeks, most bones are hardening, but the skull stays soft and flexible to help with delivery.

What You Might Notice at 33 Weeks Pregnant

Week 33 tends to bring a mix of a growing belly and the physical demands of late pregnancy. Here's what commonly shows up:

Shooting nerve pain (sciatica), as the growing uterus puts pressure on the sciatic nerve.

Increased pelvic pressure, as your baby grows and takes up more room.

More frequent urination, as the growing uterus presses on your bladder.

Backaches, as your center of gravity continues shifting forward.

Braxton Hicks contractions, appearing as occasional, painless tightening in the belly.

Swelling in the feet and ankles, especially by the end of the day.

Trouble finding a comfortable sleep position, as the belly grows large enough to limit your options.

It's also completely normal to have few or no symptoms yet. Symptom timing and intensity vary widely from person to person and even between pregnancies for the same person.

What's Happening in Your Body

Bones are hardening throughout the body, except the skull, which stays soft.
The soft skull bones help the head shift slightly during delivery.
Pelvic pressure and frequent urination often increase as your baby grows.
About 7 weeks remain until a typical full-term due date.

Tips for Week 33

Try a maternity support belt if pelvic pressure is bothering you.

Do gentle stretches or prenatal yoga if sciatica-type pain shows up — ask your provider first if it's severe.

Empty your bladder fully when you go, and don't hold it in longer than needed.

Keep taking your prenatal vitamin — steady nutrition continues to matter through the rest of pregnancy.

Start discussing your birth plan in detail with your provider, including pain management preferences.

Tips for Partners

Offer a hip or lower back massage if sciatica-type pain is bothering your partner.
Be patient with more frequent bathroom trips — it's the uterus pressing on the bladder, not a choice.
Help research or finalize birth plan details together.
Take on more physical tasks as pelvic pressure and discomfort increase.

FAQ

How big is my baby at 33 weeks pregnant? About the size of a pineapple — roughly 43.7 centimeters long, measured head to heel, and weighing around 1,918 grams.

Why does my baby's skull stay soft when other bones are hardening? The cranial bones stay soft and somewhat flexible so they can shift and overlap slightly, helping the head descend through the birth canal during delivery.

When will my baby's skull bones fully harden? This typically continues over the following months and years after birth, which is also why newborns have soft spots (fontanelles) that need gentle handling.

Why do I have shooting pain down my leg? This is often sciatica, caused by the growing uterus putting pressure on the sciatic nerve. Gentle stretching can help, but mention severe or persistent pain to your provider.

Why am I urinating so often now? The growing uterus is pressing on your bladder, leaving less room for it to fill before you feel the urge to go.

What symptoms are normal at 33 weeks pregnant? Sciatica, pelvic pressure, frequent urination, backaches, Braxton Hicks contractions, swelling, and trouble sleeping are all common at this stage.

How many weeks do I have left at 33 weeks pregnant? About 7 weeks remain until a typical 40-week due date, though every pregnancy's timeline is a little different.

Pregnancy Checklist at Week 33

Keep taking a prenatal vitamin daily
Try a maternity support belt if pelvic pressure shows up
Do gentle stretches if sciatica-type pain appears
Discuss birth plan and pain management preferences with your provider
Empty your bladder fully at each bathroom trip
Rest when you can as pelvic pressure increases
Note any regular contractions, heavy bleeding, or reduced movement and call your provider if it occurs

Related guides

32 Weeks Pregnant: Symptoms, Baby Size & What to Expect — what happened the week before, as breathing movements became more regular
Pregnancy Week by Week: A Complete Guide — see what happens in every week and trimester, from implantation to full term
How Is Your Due Date Actually Calculated? — the exact formula behind your due date, plus a free calculator

Week 33 brings hardening bones and a deliberately soft skull, with roughly 7 weeks left until a typical due date.