Factors involving economics and health play a key role but there's a growing opinion that climate change plays a role as well.
The climate crisis is affecting the way people make decisions every day.
These can be routine daily choices about what groceries to buy, or more complex considerations, like where to live or work.
MORE: Atlantic hurricanes are intensifying faster due to warmer water, study shows
But now, more people are even factoring in climate change when planning their families.
"Folks are either choosing not to have children or having fewer children than they consider ideal in large part because of climate change," said CSU East Bay Assistant Professor of Sociology Amara Miller. "So, while there are other factors, climate change is a growing reason why."
It's turning into a global opinion.
This year, Hewlett Packard asked 5,000 people how climate change impacts their decisions.
Of those surveyed, 91% said they have anxiety about the climate and 53% percent of that group said climate has impacted their perspective on having more children or any at all.
MORE: SF de Young Museum exhibit explores indigenous views on climate change
"This trend of folks having fewer kids than they would like to or not having kids at all when they would ideally like to have children, I think it's a sign of how dire the climate change situation is," Miller said.
Miller says many parents say they simply don't want their children growing up in a world of natural disasters caused by climate change.
But others, including Kristen Weaver, say their decision comes from climate experts suggesting having fewer kids than originally planned can help combat climate issues.
"I originally anticipated that I might have two or three, and I ultimately decided to have one," Weaver said. "There were a number of factors that played into that -- it wasn't just climate change. But, seeing that information really confirmed my decision to just have one child."
"The fact that anyone is making a decision not to have children because of climate change or having fewer children is very heartbreaking," Miller said. "I hope it spurs some action at these global levels, both among governments and corporations. Because it doesn't have to be this way."