Dixie Chicks' Emily Robison Is Pregnant!

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Baby on board!

Congratulations are in order for Emily Robison, who is pregnant with her fourth child -- and first with boyfriend Martin Strayer.

The Dixie Chicks singer's rep confirmed the happy news to Us Weekly on Thursday, adding "She's excited!" (Robison, 39, is due in early September.)

The baby boy or girl will join older siblings, twins Juliana Tex and Henry Benjamin, 7, and Charles Augustus, 9, who are Robison's kids with her ex-husband, Charlie Robison. The couple divorced in August 2008 after nine years of marriage.

Robison is currently is part of the country music and folk duo, Court Yard Hounds, which she started with her sister and fellow Dixie Chicks star Martie Maguire in 2010.