pregnancy week 31 baby size

Pregnancy Week 31

Discover your baby's developments now that you're 31 weeks pregnant, and learn to practice labor techniques for a more relaxed and easier delivery experience.
how big is baby week 31
How Big is Baby? 

Your baby is about as long as a bunch of leeks, and she will now gain as much as a half pound per week until she's born.

Baby's Length: 16.18in.
Baby's Weight: 3.31lb.

Mom’s Changing Body

You may be noticing more hip and lower-back pain. What gives? Pregnancy hormones are relaxing the ligaments and tendons throughout your pelvic area so that the bones can spread to make room for delivery. Your expanding uterus may also be putting some pressure on the sciatic nerve, which runs from your lower back to your buttock and hip area and down the back of each leg, triggering chronic tingling or numbness along its path—a condition called sciatica. But it's usually not serious, it won't affect the baby and it will likely become less intense as he shifts around in there.

Baby's Development

Your baby is gaining more weight than height at this point. Because she's too big to stretch out, she's now forced into the fetal position, which she'll stay in until birth. This week also boasts some exciting reproductive developments. Having a boy? His testicles are moving through the groin on their way into the scrotum. And if you've got a girl in there, her clitoris is already relatively formed.

baby development week 31

Weekly Tip

Strangers on the subway reach out and touch your belly. A woman at the grocery store wrongly warns you against having sex ("It will make you go into early labor!"). Your neighbor asks if you're planning on circumcising your little boy (and clearly has strong opinions on the subject). Sound familiar? Now that your belly is front and center, chances are it'll attract a lot of attention and unwanted pregnancy advice. Just laugh it off and try not to let the comments worry or sway you. Your opinion and your doctor's are the only ones that matter; simply deem the rest amusing distractions.

ultrasound week 31
Week 31 Ultrasound

This image gives a close-up view of the lower end of your unborn baby's spine. You can see the spinal cord protected by the bright white bones of the spine.

Credit: American Institute of Ultrasound in Medicine -

What Week 31 of Your Pregnancy Is Really Like

Pregnancy Confidential Podcast

What Happens in the Delivery Room, Stays in the Delivery Room

At Week 31, you're probably finding your mind ever-­wandering back to the elephant in your third trimester room: how you're actually gonna birth this sucker. While the physical realities of having a baby are surely present on your mind, you're also bound to be curious about what goes on around you when you're giving it the ol' heave-­ho. Who do you let in the room with you? Will you really do something as horrific as poop in front of everybody? And will you even care? This week's podcast lets you in on the deepest darkest secrets of the delivery room, so you know just what to expect when you're done expecting.

This Week's To-Do List


This Week’s FAQs


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