The star, known for her hilarious role as Elliott in US comedy show Scrubs, also revealed the name of her daughter - Frankie!
Sweetly named after her grandfather, Sarah's daughter has already been in the world for a little while, with the star only just revealing her arrival.
'I'm madly in love with my kid', Sarah told Us magazine. 'It's been really fun.'
The actress, who recently starred in the family comedy Mother's Day, notes how time has just been escaping her and her family.
'It's really weird - it's going so fast that the other day, someone asked me [how old Frankie is], and I gave a number that's two weeks younger. And I'm like, "Why am I lying about my daughter's age?"'
Sarah and Jamie also have a six-year-old son named Charlie, who suffers from Kawasaki disease. Diagnosed at the age of two, the autoimmune disease inflames the blood vessels and causes high temperature, a rash, dry lips and red eyes.
It took his parents a long time to get a diagnosis: 'It was a very difficult time because Charlie was misdiagnosed a lot, and we fought really hard to get him seen by a specialist,' Sarah revealed.
She spent over a week researching her son's medical problems, and finally found a website about Kawasaki disease that listed most of Charlie's symptoms. However, the treatment window was only open for 10 days, meaning that those who didn't receive it would develop a one in four chance of developing heart disease.
Sarah with her Scrubs co-star, Zach Braff
Sarah was intent on finding a doctor who would help her son, and he finally got the treatment just after the 10-day window.
'Thank god he's okay. Kawasaki experience is different, but one common thing for KD parents is that they go through a lot of misdiagnosis.'