Pop star Nadine Coyle is expecting a baby.

The former Girls Aloud singer, 28, shared the happy news with fans by posting a snap of herself on Instagram.com, alongside the caption, "I am having a baby".

The singer will be the first member of the Biology hitmakers to become a mother.

Coyle has not gone public with the name of the father, but she was last linked to U.S. businessman Waz Ashayer in 2012.

Girls Aloud split in March (13) after completing a 10 year anniversary tour.