When girls want a baby, we call it "baby fever," meaning "the longing to have a child of one's own."

The feeling is kicked off by seeing or holding a child and can be very overwhelming, leading to a deep longing to have their own baby.

Believe it or not, baby fever is a real thing. It's an actual physical and emotional phenomenon and studies have shown that anyone can develop it, although it might vary in intensity from person to person and some people might not even feel it.

And it's not just women who get baby fever — in fact, men get baby fever, too. However, women tend to be more prone to having "baby fever" because our biological clocks are telling us that it's time to have a baby if our biological baby-making window is starting or just dwindling.

RELATED: The Strange Thing That Makes You Want To Have A Kid ASAP

Why do I have baby fever?

Scientist Gary L. Brase at the Department of Psychology at Kansas State University decided to tackle this phenomenon in 2011 in a series of studies that aimed to determine if there were biological causes for "baby fever" and why people feel it.

The study found that out of 853 nonstudent young adults and 337 college students, three factors are responsible for the underlying desire to have a baby including positive exposure, negative exposure, and tradeoffs such as trading time, intimacy, financial resources, etc.

The study also noted that baby fever is unrelated to sexual motivation and cultural expectations as the desire for sex was quite different from the desire to nurture and parent. 

Baby fever is also caused by a romantic emotional reaction. When a woman feels this intense longing to have a baby, that longing then releases oxytocin from the brain. 

That feeling of seeing a cute baby sparks fast brain activity in our orbitofrontal cortex, which is the area in our brain responsible for our emotions and pleasure. That's why, when you're in your 20's or thirties, a woman's (or man's!) brain might suggest that it's a good time to have a child.

Getting baby fever doesn't necessarily mean you want kids.

The biological responses that cause baby fever explain why you might even get this feeling when you're a teenager or in your early 20's, or if you don't want any more kids.

It also seems like the choice is up to you whether or not you get baby fever. 

In a 2019 study, 4,500 women in the U.S. born between 1957 and 1965 were questioned during their childbearing ages on expectations of having children. The results found that those who said they don’t want to have children actually don't have kids and vice versa for those who said yes. 

So in the end, having baby fever doesn't mean you actually want kids because it all comes down to the combination of emotion, timing, and biological instinct when having a baby.

RELATED: I Wanted A Baby My Whole Life — And Now I Regret Having One

What do you do when a guy wants a baby and you don't?

This is one of the hardest decisions in a relationship or marriage because both parties need a unanimous decision as having a baby is a really big deal. 

If this happens, you and your partner need to have a serious conversation on your future and if that includes a baby or not.  

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Megan Hatch is a writer at YourTango who covers news & entertainment, love & relationships, and internet culture. Follow her on Twitter and Instagram.