Not pregnant? No plans for it in the near future? Suddenly see a cute baby and think about having one of your own even though yours are older? See cute baby clothes and start making plans for how you would dress yours? Feel any of those things? You're not alone- the term for those desires, despite not truly wanting kids is "baby fever" and it will most likely strike. When it does, it strikes at odd times.
Baby fever is the term coined to reflect the biological urge to create a new human. Most people will get some form and some intensity, even if they do not want kids. Men get it just like women do but typically not as strong as their female counterparts.
The main cause of "baby fever" is to kick us into baby-overdrive in order to ensure the continuation of the population. There are many theories about why people get baby fever and there were conflicting views if it even existed, so a team of researchers (husband/wife team) conducted a decade-long study and the results were released in 2011.
There are a few theories to what causes it. The main theory seems to be that it's a biological drive to keep up with the human population, back when families had to have many kids in order to ensure at least one or two would survive into adulthood to carry on the family genes. It's also true that there is a "biological clock" factor at play- when women reach certain ages, they get baby fever as a way of their body trying to make a baby before they lose their fertility.
It was found that both men and women get it and were much more likely to get it if they were exposed to cute, playful and happy babies and less likely if exposed to sick, colicky or otherwise bad experiences.
It is important, however, to not cave in when you have baby fever and wait until it passes- you don't want to end up getting pregnant during a time you're feeling delusionally interested in babies but don't truly want to add a new addition now or start your family just because you were fantasizing over your next bundle. Remember, baby fever is a phase- it doesn't mean you're ready or wanting another baby. It's biological in nature.