CHICAGO (CBS/AP) — Chicago West. That’s the name given by Kanye West and Kim Kardashian to their new baby girl.

Mom made the announcement Friday on her app without explanation. Chicago was born Monday at 12:47 a.m., weighing in at 7 pounds, 6 ounces. She joins big sister North and middle brother Saint.

Why not Mid West–to go along with the theme started by older sister North West? Perhaps for child No. 4.

Dad, of course, is from Chicago.

“Kanye and I are happy to announce the arrival of our healthy, beautiful baby girl,” Ms. Kardashian West wrote in a post titled “She’s Here!”

Chicago was born Monday via gestational carrier, meaning Kardashian West’s fertilized egg was implanted into a surrogate.

The rapper and the reality star chose to use a gestational carrier after Kim suffered pregnancy complications with her two older children. She said her doctors told her it wasn’t safe for her to carry another baby.

The couple also has a son named Saint.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)

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