You probably can't stop touching it, and it might seem like it's getting bigger by the day.

Chances are, you're completely obsessed with your baby bump and the amazing little being growing inside it. But how much do you actually know about the changes that are unfolding on the outside — and the bustling activity that's happening on the inside?

Here are 10 fun facts about your ever-expanding baby bump.

It probably won't be noticeable in the beginning

Sure, you'll likely feel a whole lot different inside once you find out you're pregnant. (So exciting! And also … the morning sickness.) But aside from that big smile on your face, you might not look different on the outside.

During those early weeks of pregnancy, your baby is still teeny-tiny. Even at 4 weeks, she's only the size of a poppy seed! So chances are, your bump won't start to show until you hit the 3-month mark — when your baby is about the size of a lime.

But once you begin showing, your belly will grow fast

Your skin may show it too. If you're among the more than half of pregnant women who develop skin streaks, you'll start to notice them when you're between 13 and 21 weeks along. 

These marks form when the supporting layers under your skin get pulled tight as your belly expands. The streaks might become darker and more prominent when your tummy really starts to stretch around the 35-week mark.

There's no proven way to prevent stretch marks, and they'll fade after you give birth. But in the meantime, try to embrace them. Your body is growing to make a baby!

Those butterflies in your belly might not be pre-baby jitters

If you feel a fluttering sensation, it could very well be your baby squirming or fidgeting. This early movement — called quickening — usually starts when you're 4 or 5 months pregnant.[1]

From there on out, your baby will only get more active. By 6 months, you might start to feel tiny feet pitter-pattering. And by 28 weeks, your doctor will want you to start "counting kicks," or fetal movements, to ensure everything is progressing as expected.

That dark line that's forming is totally normal

Surging pregnancy hormones can cause a number of skin anomalies, from darker areolas to hyperpigmentation on your face. They're also responsible for your linea nigra — the dark, vertical line extending from your belly button to your pubic area that becomes noticeable around 23 weeks. It's completely normal, and it'll fade a few months after you give birth.

Your innie will probably become an outie

If your belly button is an innie, it won't stay that way for long. Around 26 weeks, your expanding uterus will cause your belly button to protrude, making it look like an outie.

Like most of the other changes happening to your body these days, this one is harmless — and things will go back to normal after you have the baby and your stomach deflates.

What if your belly button is pierced? As long as your belly button piercing is healed (as in, not freshly done) and healthy, there's no reason to remove your navel ring right now. At the end of pregnancy, you'll want to switch to wearing a straight plastic bar, which may feel more comfortable and is safer than metal jewelry in the event you need an emergency C-section. If at any point your stretching belly makes your piercing irritating, you might want to take it out. You should also remove it if the skin around the ring seems red or inflamed, which could be signs of infection. 

The inside of your belly is warm and cozy — but it isn't soundproof

By as early as 16 weeks, your baby's ears are developed enough that she can hear your voice. For now, she's happy to just be a listener. But by 26 weeks, her brain is developed to the point where your baby can respond to stimuli. So don't be surprised if she gives a little kick when you talk or sing to her!

Speaking of songs, you might want to think about finding a special one to play for your baby. While there's no proof that playing certain music (like classical) will boost your baby's IQ, sharing your favorite tunes can still be a fun bonding experience.  

Of course, everything will sound a little muffled in there. To get an idea of what things sound like for your baby, try talking with your hand over your mouth. That's what your baby hears!

Your baby likes when you touch your belly

Touching, patting or holding your bump doesn't just make you feel warm and fuzzy, it might make your baby feel good too. Research shows that fetuses respond powerfully to belly touches by moving around.[2] So keep rubbing that bump! 

It can stimulate your baby, which is especially helpful when you start counting kicks. And of course, it's an amazing way to bond. The more you interact with your baby now, the more familiar she may be with the world outside the womb once he's born.

Measuring a little big or small is usually a-okay

At each prenatal visit, your practitioner uses a tape measure to check your fundal height — the distance from your pubic bone to the top of your uterus. That number in centimeters roughly equals the number of weeks along you are.

But 1 or 2 centimeters in either direction is nothing to worry about — and it doesn't mean that your baby isn't growing fast enough or will be too big to deliver vaginally.

Often, measuring big or small during pregnancy could just mean that your due date is off by a few days or a week, or that your baby is sitting high in your uterus.

Your belly could make things a little uncomfortable towards the end

Your baby gets a whole lot bigger — growing from about 2 pounds at the end of the second trimester to somewhere between 6 and 9 pounds at the end of the third trimester.

As your little one takes up more and more space in your belly, you might start noticing some not-so-fun changes. You might feel sharp pains as your round ligaments stretch to accommodate your growing bump. Heartburn could also become an issue, since your expanding uterus is now pushing on your stomach.   

Things are getting cramped for your baby too, so don't be surprised if you start to notice fewer hard kicks and more jabs from knees and elbows during the last few weeks of your pregnancy.[3] (Always check in with your practitioner about any changes in fetal movement, though.)

The good news is that the two of you are almost at the finish line. It won't be long now before you finally get to meet!

Your bump won't disappear right after giving birth

After you welcome your little one to the world, your postpartum recovery period begins. It takes some time for your uterus (and abdominal muscles and skin) to adapt, just like they did during pregnancy.

If it seems like your belly still has a bump-like appearance many months after giving birth and feel soreness around your belly button or lower abdomen, you could have diastasis recti — which can happen when a growing belly causes abdominal muscles to separate and protrude slightly. Sometimes diastasis recti resolves on its own, but talk to your doctor if it's not easing up. Most of the time the problem can be fixed with targeted core exercises.

In the meantime, think about all the incredible things your body has done over the last 40 weeks. And soak up this special time with your adorable newborn!

From before you begin to show to the time your baby finally arrives, your belly is growing and changing. And now that you know more about your baby bump, you probably appreciate it more too. Not only is it the warm, cozy, nourishing home where your little sweet pea spends her first nine months, it's also a way for you and your baby to bond — and even get to know each other — before she's born.