The couple announced in May that they are expecting their first child together later this year.
"Having a kid is a big deal to both of them - they didn't take this lightly," a source told US Weekly of their decision to have a family.
"They planned for this baby and now seemed as good of a time as ever. They really will be the best parents."
The insider added that Faris has so far had an easy pregnancy, saying: "Maybe it's just her energy, but she hasn't been having trouble with the pregnancy at all!"
In 2011, Faris revealed that Pratt would like to have a big family but that the couple are aware of the difficulties of timing in the film industry.