The actress, who is married to musician Alec Puro, admits the first four months of her pregnancy went smoothly, but she was "completely crushed" when the results of her second trimester blood tests came back abnormal.
In a blog for People.com, she writes, "My husband and I sat in the genetic counsellor's office discussing our 'options'; if the test was in fact positive for a serious birth defect. They were throwing out everything from spina bifida to Down syndrome.
"I was completely crushed. I was already so attached to my little girl. She has a name. I talk to her, I sing her songs... she has to be OK."
Sokoloff underwent more tests to check for an infection or defect and admits she suffered 10 "agonising days" waiting for a diagnosis.
She recalls, "I started to feel like I had been punched in the gut. My positive attitude that I tried so desperately to hold on to went flying out the window and was replaced with complete and utter fear.
"The next few days were spent on the couch covered in tears. I literally couldn’t function...
"After 10 agonising days, our amnio results came back showing a perfectly healthy little girl. The abnormal blood work was, in fact, a false positive. I... then returned to my oh-so-familiar state of hysterical crying. Only this time, they were happy tears."
Sokoloff and Puro are expecting their first child this winter (11).