HOUSTON -- Doctors in Houston have successfully separated toddler girls who were born in 2016 conjoined at the chest and abdomen.

A spokeswoman at Texas Children's Hospital said 13-month-old Anna and Hope Richards were in good condition Tuesday. Lindsey Fox says separation surgery was done Jan. 13 and announced Monday.

Fox says the twins join two brothers and their parents, Jill and Michael Richards, of North Texas.  Fox declined to provide a hometown or more specifics about the family, as the parents focus on their daughters' recovery.

Officials say a routine ultrasound revealed the girls were conjoined. The twins were born premature, at just over 35 weeks, on Dec. 29, 2016, at Texas Children's Pavilion for Women. Their combined weight was 9 pounds, 12 ounces.

Further details weren't provided on their prognosis.