But not all changes are visible.

In fact, some of the biggest changes happen in her brain.

When a mother sees her newborn for the first time, it's love at first sight, literally.

That's because once she gives birth, core regions of her brain's reward network kick in.

They signal the release of feel-good hormones like dopamine and oxytocin into her blood, which immediately triggers a strong connection of love and devotion to her newborn.

In fact, studies show that recent mothers have similar levels of oxytocin as romantic couples who are newly in love.

And human moms aren't alone here.

Scientists discovered that rodents got a bigger kick of dopamine from feeding their pups than from receiving injections of cocaine.

What's more, brain scans reveal that a human mom has a similar experience when she sees her infant smiling.

But it's a different story when her baby is crying.

Those cries activate a network in the mom's brain known as the emotion regulation network.

It includes the prefrontal and cingulate control systems, which help control her emotions.

And that's important, since it can be easy to lose your temper when you're running on very little sleep and are distressed by the baby's cries.

And while motherhood can be exhausting, new moms are actually more alert than normal thanks to their brain's salience network.

Scientists think giving birth activates this network to help a mother detect threats and protect her infant from harm.

Especially in dangerous situations when that network can help ramp up adrenaline.

But on a daily basis, Mom needs to understand her newborn's needs.

To accomplish that, she uses empathy, which comes from her brain's social network.

It involves the insula and amygdala, which researchers found became more active when moms looked at photos of their babies in distress compared to neutral photos.

But it's not just the mom's brain that changes.

Research shows that a dad's brain releases oxytocin when he interacts with his baby, too.

This is often accompanied by a surge of another hormone, prolactin.

It's often called the milk hormone because it triggers the production of breast milk.

But men can produce it, too, and researchers have found that dads who frequently played with their babies had higher prolactin levels in their blood than fathers who didn't.

They were also more responsive to their baby's cries.

So, in the end, having a child is a big change.

Not just for your lifestyle, for your brain, too.