Week 40 Pregnancy: Pregnant Belly, Ultrasound, & Baby

Week 40 pregnancy - Pregnant Belly Ultrasound and Baby

It’s been 40 weeks — weeks which may feel simultaneously like they’ve dragged on and flown by. Your baby will be here very soon! Let’s talk about that beautiful pregnant belly, how ultrasound may be used in week 40 of pregnancy, and discuss meeting your precious little one face to face for the first time.

Estimated reading time: 8 minutes

Updated August 6, 2021

Week 40 Pregnancy: A Look Inside

As we’ve done each week in our Pregnancy Week-By-Week articles, let’s take a look inside at baby. The early weeks and months were packed with huge changes, new organs and systems, and exciting developments! In recent days, we haven’t had as much flashy news. However, it is definitely its own type of exciting to know that this week baby is gaining weight and polishing up those lungs for his first cries.

How Big is Baby?

At week 40 of your pregnancy — 38 weeks since he was conceived — baby is around an average weight of 7 2/3 pounds. He measures in at around 14 3/4 to 15 1/4 inches from crown to rump, and 20 2/3 inches in total length (1). These are general numbers, of course, representing only the average size. In reality, your baby is probably anywhere between 6 and 9 pounds, and 18 to 21 inches long (2).

Week 40 Pregnancy: Pregnant Belly

As you arrive at your due date, let’s take one more look at your (now rather large) belly bump. If you’re still measuring fundal height, you will find that the top of your uterus is 14 1/2 to 16 inches from the pubic symphysis and an astonishing 6 1/2 to 8 inches above your belly button.

Your bump enters rooms ahead of you, blocks the view of your own feet, and makes it a challenge to get out of a chair. It may be covered in stretch marks, may itch, and may hurt. But… it is also a beautiful illustration of how your body has performed the amazing feat of creation. And it is the only home your little one has known so far.

If you’re not someone who has documented weekly bump pics, or if you’ve shied away from the camera as you’ve gotten bigger, it’s time to stop what you’re doing and take a picture of your beautiful bump! You will thank yourself later for preserving the memory.

Week 40 Pregnancy: Ultrasound

As you reach week 40 of your pregnancy and baby has not yet arrived, your doctor or midwife may want to do some tests to be sure everything still looks good with you and the health of your baby.

Biophysical Profile

A biophysical profile (BPP) is done to assess baby’s health, especially if you’re overdue. The BPP scores baby on five categories: fetal breathing movements, fetal body movements, fetal tone, amount of amniotic fluid, and reactive fetal heart rate (also called a non-stress test or NST) (1). The NST tracks the baby’s motion with external fetal monitors, but the other four tests are done with an ultrasound. Combined, these tests help to give the doctors an idea of the overall health of your baby.

Should I Be Worried?

It may sound concerning that your healthcare provider wants to run extra tests, but this is no cause for alarm. Testing after the due date is really just a matter of routine. Normal pregnancy lasts from 37 to 42 weeks, and only about 5% of babies are born on their due dates. At week 40 of pregnancy, you’re not overdue, your provider is simply being thorough and cautious.

A couple more weeks down the road — after week 42 of pregnancy — there is a small risk (5 – 10%) of post-maturity syndrome. This means that the placenta stops functioning well, baby’s growth slows or stops, and there’s a gradual increase in the chance of harm to the baby. In cases where there is any concern, labor may be induced. Still, healthy babies are born after 42 weeks all the time!

Week 40 Pregnancy: Baby!

By the end of this week, you just might be holding your baby! We don’t have the time to get into all the specifics of labor (check out our posts about labor & birth or learn more about the Kopa Birth® online childbirth course), but let’s touch on the moment you get the first glimpse of the new love of your life. What can you expect?


Vernix caseous is the white, waxy or creamy substance that has protected baby’s skin from fluid damage while in the womb. Although it may still be very visible on his skin when he’s born, by week 40 pregnancy, much of the vernix may have worn away. If it’s still there, it’s most likely to be found in the folds of baby’s skin and elbow and around the ears. Vernix used to be washed away shortly after birth, but it’s becoming more common not to wash it off and instead rub it in, as we now know that it helps the skin adapt to life outside the womb (4).

Vernix is the white, creamy substance covering this little bundle o’ joy!

Cone Head

The bones in baby’s head are not yet fused together. They’re made to move and overlap, making the circumference of the head smaller, as baby passes through the narrow birth canal. He or she may have an elongated head after birth, especially if the pushing stage was long and baby spent a while in the birth canal, but it will round out on its own within a few days. (The bones won’t fuse until your little one is around two years old, because the brain does a lot of growth and development in that time.)

And speaking of baby’s head, it’s huge. 😉 It accounts for about 25% of baby’s total length, and the diameter is similar to the diameter of his chest. As your little one grows, his body and limbs will catch up.


Baby doesn’t have a lot of fat under his skin, which makes the skin look wrinkly. It may also be a strange color. This varies by baby and is, of course, affected by ethnicity and natural skin tone. Many babies are born with reddish skin, or it may appear sort of blue or purple at first. His hands and feet may even remain blue for a few days, which is simply the result of immature blood circulation.

Puffy Face or Eyes

Being born is hard work. If you were submerged for nine months and then squeezed through a very narrow passage, you’d probably come thorough it with puffy eyes, too! While mom gets credit for the hard work of labor (and she should!), baby also went through quite an ordeal. All that squeezing is bound to leave a mark.

Enlarged Genitals

As you’re counting fingers and toes and taking in every detail of your new love, you may notice that his or her genitals and/or breasts may be enlarged. (This is true for both genders.) This is due to the hormones that came from your body, and it will resolve within a couple of weeks.

Umbilical Cord

Your baby will still have a bit of the umbilical cord attached. It’s usually a yellowish color at first, and will turn darker and eventually be black before it falls off. It isn’t the prettiest feature — not nearly as cute as the little belly button that will be on his adorable little round tummy soon — but it is the last piece of the incredible link between the two of you that provided your baby with everything he needed to grow and thrive.

It’s true that your little one won’t look like the babies on commercials… yet. Those babies didn’t start that way either, though. Despite it all, your little one will be beautiful, and your eyes will see absolute perfection.

If your little one doesn’t arrive this week, check back next week for Week 41 Pregnancy and Beyond: Risks, Tests, & Post-Term.

Kopa Birth’s online childbirth classes allow you to prepare for a natural childbirth from the comfort of your own home, 24/7. Enroll today in our free online childbirth class to learn more about preparing for a natural hospital birth.


  1. Glade, B.C., Schuler, J.  (2011).  Your Pregnancy Week by Week, 7th edition.  First Da Capo Press.
  2. The American College of Obstetricians and Gynecologists.  (2010).  Your Pregnancy and Childbirth Month to Month, 5th edition.
  3. Simkin, P. (2010). Pregnancy, Childbirth and the Newborn, 4th edition. Meadowbrook Press.
  4. Singh, G., & Archana, G. (2008). Unraveling the mystery of vernix caseosa. Indian journal of dermatology53(2), 54–60. https://doi.org/10.4103/0019-5154.41645

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Meet Katie Griffin

I’m a registered nurse, Lamaze certified childbirth educator, and the mother of 7. I help women realize their dream of a natural, intimate, and empowering hospital birth.

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It’s been 40 weeks — weeks which may feel simultaneously like they’ve dragged on and flown by. Your baby will be here very soon! Let’s talk about that beautiful pregnant