Kellie Martin Welcomes Daughter Olivia James

Kellie Martin‘s little lady is here!

Born Saturday, Feb. 13, daughter Olivia James Christian weighed in at 7 lbs., 15 oz. and measures 20 inches long, her rep tells PEOPLE exclusively.

Olivia joins big sister Margaret Heather, 9.

The actress announced the arrival of her second child with husband Keith Christian on Twitter Thursday.

“She’s finally here,” Martin, 40, captioned a photo of her two girls.

The former ER star was five months along when she announced she and Christian were expecting another baby. But due to her severe morning sickness, Martin’s big reveal to her firstborn came much earlier on in the pregnancy.

“She took the news really, really well,” Martin said of daughter Maggie during a segment on Hallmark’s Home & Family in September.

“I told her way earlier than I expected to because I was so sick that I didn’t want her to think there was something wrong with Mommy.”

And Maggie has been prepping for her new role ever since finding out she had a baby sister on the way. In between sharing sweet snapshots of her growing bump, Martin has posted several photos of her daughter giving her baby belly love and testing out the new stroller.

“Someone’s getting pretty excited to be a big sister,” the mom-to-be captioned a picture of Maggie trying out her sister’s new ride with a teddy bear.

— Anya Leon with reporting by Gabrielle Olya