Week 40 of Pregnancy: Your Baby Is the Size of a Pumpkin

TL;DR

• Your baby is about 51.2 cm long — roughly the size of a pumpkin
• Your baby is fully developed and ready to meet you
• Only about 5% of babies arrive on their due date — most come within a week or two on either side
• Your due date is here — remember, babies arrive on their own schedule

Your Baby This Week

This is the week. Your due date. Forty weeks of growing, developing, and preparing — and your baby is ready.

At about 51.2 cm and roughly 7.5 pounds (though healthy birth weights range widely from about 5.5 to 10 pounds), your baby is fully developed and waiting for the signal to begin their journey into the world. Every system is online. Their heart has been beating for about 37 weeks. Their lungs are coated with surfactant and ready to take that first breath. Their eyes can focus on objects 8-12 inches away — exactly the distance from the crook of your arm to your face when you hold them for the first time.

Your baby's brain has about 100 billion neurons — as many as there are stars in the Milky Way. Those neurons are forming connections at an astonishing rate, and this process will continue throughout childhood. But the foundation has been laid, right here, right now, inside you.

Your baby is building up their last reserves of fat, storing energy for the demanding work of being born and adjusting to life outside. They're curled up tightly in the fetal position, head down (in most cases), waiting. Your baby has been listening to your heartbeat for months. It's the sound they know best in the world. And soon, they'll hear it from the outside — pressed against your chest, skin to skin, breathing air for the first time.

Your Body This Week

If you're reading this on your actual due date and there's no baby yet — you're in very good company. Only about 5% of babies arrive on their due date. Most come within a window of two weeks before or after. Your baby isn't late. They're just taking their time.

That said, the waiting can be excruciating. You've been pregnant for nine months. Everyone is texting to ask if "anything is happening yet." Your body is uncomfortable in ways you didn't know were possible. You might swing between desperately wanting this baby to come out and being terrified about what comes next. This emotional rollercoaster is completely normal.

Physically, you might be noticing signs that labor could be approaching — or you might not be noticing anything at all. Common pre-labor signs include: losing your mucus plug, a bloody show, loose stools, a burst of energy (nesting), lower back ache, menstrual-like cramps, and Braxton Hicks contractions that might feel stronger than before. Some people experience all of these; some experience none before labor begins suddenly.

Your provider is monitoring you closely at this point. They'll likely discuss a plan for what happens if you go past 41 weeks, which may include increased fetal monitoring, non-stress tests, and eventually, discussion of induction. The goal is always the same: a healthy parent and a healthy baby, however they arrive.

If you're feeling anxious, overwhelmed, or emotional — that's okay. You're on the threshold of the biggest change of your life. Give yourself permission to feel all of it.

Common Questions at Week 40

What if I go past my due date?

Going past your due date is common and usually not a cause for concern. Your provider will increase monitoring — typically with non-stress tests to check your baby's heart rate and ultrasounds to measure amniotic fluid levels. Most providers will discuss induction between 41 and 42 weeks, as the risk of complications increases slightly after that point. But many, many healthy babies are born at 41 weeks with no issues at all.

What are the signs that labor is starting?

Labor can begin with regular contractions, your water breaking, a bloody show, or intense lower back pain that doesn't let up. Sometimes it starts with mild contractions that gradually build; other times it comes on quickly and intensely. There's no single way labor begins — and your experience may be completely different from anyone else's. The key signs to watch for: contractions that are regular and getting closer together, water breaking (a gush or steady trickle of clear fluid), or any bleeding.

Should I ask to be induced?

This is a personal decision to make with your provider. Some people prefer to wait for spontaneous labor; others are ready to be induced for physical or emotional reasons. If you're at 40 weeks with an uncomplicated pregnancy, your provider may offer induction or suggest waiting a bit longer. There's evidence that induction at 39-40 weeks can reduce certain risks, but it also changes the labor experience. Have an honest conversation with your provider about the risks and benefits for your specific situation.

What should I do while I wait?

Be gentle with yourself. Rest, eat well, stay hydrated, and do things that bring you comfort. Take a walk. Have your favorite meal. Watch a movie that makes you laugh. Write a letter to your baby. Call a friend. Take a nap. Avoid the temptation to Google "how to start labor at 40 weeks" for the hundredth time. Your baby will come. It might be today, it might be next week — but it will happen, and when it does, everything changes.

This Week's Tip

Your due date is here. Remember, babies arrive on their own schedule. A due date is an estimate — a midpoint in a window of time during which your baby is likely to arrive. It's not a deadline. Try to let go of the specific date and trust that your body and your baby are communicating in ways you can't consciously control. The hormones that start labor — oxytocin, prostaglandins — are influenced by relaxation and safety. So the best thing you can do right now is exactly what feels hardest: relax, breathe, and wait.

Milestone: Due Date

You've reached your due date — the day you've been counting down to since that first positive test. Forty weeks. Whether your baby arrives today, tomorrow, or next week, this milestone marks the culmination of an extraordinary journey. You grew a human being. From a single cell to a fully formed person with fingerprints, hiccups, and a heartbeat you'll recognize anywhere. Whatever your pregnancy has looked like — easy, hard, complicated, joyful, scary, all of the above — you did it. And the best part is just about to begin.

Sources

• American College of Obstetricians and Gynecologists (ACOG) — Third Trimester
• Mayo Clinic — Fetal Development: The Third Trimester

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