Week 37 of Pregnancy: Your Baby Is the Size of Swiss Chard

TL;DR

• Your baby is about 48.6 cm long — roughly the size of a bunch of Swiss chard
• Major milestone: your baby is now considered early term
• Your baby is practicing breathing, sucking, and gripping — getting ready for life outside
• Finish any last preparations — your baby could arrive any day now

Your Baby This Week

Congratulations — your baby is now considered early term. This is a significant milestone. While "full term" officially starts at 39 weeks, reaching 37 weeks means your baby has developed to a point where they would likely do very well if born now, typically without needing extended NICU time.

Your baby is about 48.6 cm long and weighs around 6.3 pounds, though there's a wide range of normal. They're spending these final weeks putting on weight, refining their reflexes, and practicing the skills they'll need immediately after birth. They're sucking their thumb, gripping tightly, blinking, and breathing rhythmically — inhaling and exhaling amniotic fluid to strengthen their lungs for that first breath of air.

Your baby's brain and lungs are still maturing. In fact, significant brain development continues to happen between 37 and 39 weeks — this is why ACOG recommends against elective deliveries before 39 weeks unless medically necessary. The brain at 35 weeks weighs only two-thirds of what it will weigh at 39 weeks, so these final weeks matter.

Your baby's immune system is also receiving its final boost of antibodies from you through the placenta. These borrowed antibodies will protect your baby during the first few months of life while their own immune system develops.

Your Body This Week

You're in the final stretch, and your body knows it. You might be experiencing a mix of excitement, nervousness, impatience, and sheer physical exhaustion. All of these feelings are valid.

Cervical changes may be happening — your cervix might be softening, thinning (effacing), or beginning to dilate. Your provider is checking for these changes at your weekly appointments. Some people walk around at 2-3 cm dilated for weeks before labor begins, while others go from zero to delivery in a matter of hours. There's no predicting it.

You might notice more frequent or intense Braxton Hicks contractions. These practice contractions are preparing your uterus for the real thing. The key differences between Braxton Hicks and true labor: Braxton Hicks are irregular, don't get progressively stronger, and usually stop when you change positions or drink water. True labor contractions come at regular intervals, get closer together and more intense over time, and don't stop regardless of what you do.

Lightning crotch — that sudden, sharp, shooting pain in your pelvis or vagina — might make more frequent appearances as your baby's head presses on nerves in your lower pelvis. It's startling and uncomfortable but harmless. It's just your baby settling deeper.

You might also notice a burst of energy — the nesting instinct at its peak. If you feel the urge to organize, clean, or prepare, go with it (within reason). But also make sure you're resting. You'll need that energy soon.

Common Questions at Week 37

What does "early term" mean?

ACOG defines pregnancy terms as: early term (37-38 weeks), full term (39-40 weeks), late term (41 weeks), and post-term (42+ weeks). While babies born at 37 weeks usually do well, research shows that waiting until 39 weeks — when possible — gives the brain and lungs additional time to mature. This is why scheduled deliveries (inductions or cesareans) are typically planned for 39 weeks or later unless there's a medical reason to deliver sooner.

How do I know if my water breaks?

It might be a dramatic gush or a slow, steady trickle — both are normal. Amniotic fluid is usually clear or slightly yellowish and odorless (unlike urine). If you think your water has broken, note the time and contact your provider. If the fluid is green or brown-tinged, go to the hospital right away — this could indicate meconium in the amniotic fluid.

Is it normal to feel anxious about becoming a parent?

Completely. Even if you've wanted this for years, the reality of bringing a baby home can feel overwhelming. You might worry about whether you'll know what to do, whether you're ready, whether you'll be a good parent. These feelings are universal. The fact that you're thinking about it means you already care deeply — and that's the most important qualification for parenthood.

This Week's Tip

Baby is considered early term — finish any last preparations. If your hospital bag isn't packed, do it now. If your car seat isn't installed, this weekend is the time. Make sure you know the route to your hospital or birth center, and have a backup plan for getting there. Charge your phone, prep your music or comfort items for labor, and make sure your partner or support person knows the plan. You're not being paranoid — you're being prepared.

Milestone: Full Term

Your baby has reached early term status at 37 weeks — a milestone that means their body is ready for the outside world. Lungs are producing surfactant, the digestive system is functional, and their reflexes are sharp. While the medical definition of "full term" begins at 39 weeks, reaching 37 weeks is a moment to pause and appreciate how far you've both come. From a tiny cluster of cells to a fully formed human being, ready to breathe, eat, and be held. The finish line is in sight.

Sources

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

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