At 24 weeks pregnant, your baby is about the size of an ear of corn, and the lungs have finished forming their basic structure — though they're still not mature enough to work well outside the uterus. This week also often opens the window for gestational diabetes screening, one of the more routine appointments coming up in the next few weeks.

If your dates feel confusing, remember that gestational age counts from the first day of your last period (LMP), not from conception — so "24 weeks pregnant" usually means about 22 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 23 weeks pregnant first.

Diagram comparing an ear of corn to a 24 week fetus, showing fully formed lung structure — At 24 weeks, your baby is about the size of an ear of corn, with the lungs' basic structure now fully formed.

Key takeaways

Baby is about the size of an ear of corn (roughly 30 cm, head to heel) and weighs around 600 grams.
The lungs' structure is fully formed, though they're not yet mature enough to work outside the uterus.
Gestational diabetes screening often begins around now, typically sometime between weeks 24 and 28.

What "24 Weeks Pregnant" Actually Means

Using standard gestational dating, week 24 starts about 22 weeks after ovulation, placing you near the end of the second trimester. In fetal-age terms (counting from conception rather than your last period), this is closer to "22 weeks post-conception."

This week is a commonly cited developmental milestone because it lines up with meaningful lung structure progress, and because it's often when the glucose screening window opens for gestational diabetes.

Baby Size at 24 Weeks

At 24 weeks, your baby is about the size of an ear of corn — roughly 30 centimeters long, measured head to heel, and weighing around 600 grams. (Source: Baby Your Baby, Utah Department of Health)

Lung Structure and the Glucose Screening Window

This week, your baby's lungs are fully formed in terms of basic structure, but they're not yet developed enough to work well outside the uterus on their own. (Source: Cleveland Clinic) Over the coming weeks, the lungs will keep maturing and begin producing surfactant, a substance that helps keep the tiny air sacs from collapsing once breathing starts.

Around this same stretch, many providers begin gestational diabetes screening — typically sometime between weeks 24 and 28. It usually starts with a glucose challenge test: you drink a sugary solution, then have your blood sugar checked an hour later. If you'd like to understand what the screening involves and what happens if your numbers come back elevated, our guide to gestational diabetes walks through it in detail.

Diagram showing a 24 week fetus with fully formed lung structure and early surfactant production — At 24 weeks, the lungs' basic structure is fully formed, though maturity for breathing independently is still weeks away.

What You Might Notice at 24 Weeks Pregnant

Week 24 tends to bring a mix of anticipation around upcoming screening and familiar third-trimester-adjacent symptoms. Here's what commonly shows up:

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

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

Restless legs, which some people notice more often in the evening.

Backaches, as your center of gravity continues shifting forward.

Itchy belly skin, as it keeps stretching to accommodate your growing baby.

Increased vaginal discharge, which is typically normal unless it changes color, odor, or is accompanied by discomfort.

Fatigue, which can return for some people as the body works harder to support the pregnancy.

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

The lungs' basic structure is fully formed, though functional maturity is still weeks away.
Gestational diabetes screening often begins around now, typically between weeks 24 and 28.
Movement continues to feel stronger and more distinct.
Braxton Hicks contractions may become more noticeable.
Fatigue can return as your body works harder to support the growing pregnancy.

Tips for Week 24

Ask your provider when your glucose screening is scheduled, if it hasn't come up yet.

Eat balanced meals in the days leading up to your screening — most providers don't require special prep, but ask if you're unsure.

Elevate your feet in the evening if mild swelling shows up.

Stretch before bed if restless legs are bothering you.

Rest when you can, especially if fatigue has returned.

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

Tips for Partners

Offer to go along to the glucose screening appointment — it can take a couple of hours with the waiting period, and company helps.
Take on more of the physical chores if fatigue or restless legs are flaring up.
Learn the basics of gestational diabetes together, in case screening results come back needing follow-up.
Keep an eye out for Braxton Hicks patterns, and help track when they happen if your partner wants a record.

FAQ

How big is my baby at 24 weeks pregnant? About the size of an ear of corn — roughly 30 centimeters long, measured head to heel, and weighing around 600 grams.

Are my baby's lungs fully developed at 24 weeks? The basic structure is fully formed, but the lungs aren't yet mature enough to work well outside the uterus — that maturity continues developing over the following weeks.

When does gestational diabetes screening happen? Most providers screen sometime between weeks 24 and 28, usually with a glucose challenge test.

Do I need to do anything to prepare for the glucose screening? Most providers don't require special preparation, but confirm with your provider since guidance can vary slightly.

What symptoms are normal at 24 weeks pregnant? Braxton Hicks contractions, swelling, restless legs, backaches, itchy skin, increased discharge, and fatigue are all common at this stage.

Why has my energy dropped again after feeling better in the second trimester? Fatigue can return as your body works harder to support your growing baby, even during the generally higher-energy second trimester.

What happens if my glucose screening comes back elevated? You'll typically be asked to take a longer follow-up test to confirm a gestational diabetes diagnosis — our gestational diabetes guide covers what that involves.

Pregnancy Checklist at Week 24

Keep taking a prenatal vitamin daily
Ask your provider when your glucose screening is scheduled
Elevate your feet if mild swelling shows up
Stretch before bed if restless legs are bothering you
Rest when you can if fatigue has returned
Learn what the glucose screening involves ahead of your appointment
Note any severe cramping, heavy bleeding, or reduced movement and call your provider if it occurs

Related guides

23 Weeks Pregnant: Symptoms, Baby Size & What to Expect — what happened the week before, as lung blood vessels began developing
Gestational Diabetes: What You Need to Know — what the screening involves and what a diagnosis means
Pregnancy Week by Week: A Complete Guide — see what happens in every week and trimester, from implantation to full term

Week 24 marks a meaningful lung development milestone, and it's often when the gestational diabetes screening window opens over the next several weeks.