In this Jan. 13, 2018, photo provided by Texas Children's Hospital in Houston, Jill and Michael Richards along with their two sons, Collin and Seth, spend time together with their conjoined twins, Anna and Hope Richards, before successful surgery to separate the toddler girls. The two were born in 2016 conjoined at the chest and abdomen. (Paul Vincent Kuntz/Texas Children's Hospital via AP)

Doctors in Houston have successfully separated twin toddlers who were born in 2016 conjoined at the chest and abdomen.

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

Fox says the twin sisters join two brothers and their parents, Jill and Michael Richards of North Texas. Fox declined to provide more specifics about the family as the 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.

  • In this Jan. 13, 2018, photo provided by Texas Children's Hospital in Houston, hospital personnel wheel conjoined twins, Ann and Hope Richards, to surgery to separate the toddler girls. The successful surgery was announced Monday, Feb. 12, 2018. The girls who were born in 2016 conjoined at the chest and abdomen. (Paul Vincent Kuntz/Texas Children's Hospital via AP)

  • In this Jan. 13, 2018, photo provided by Texas Children's Hospital in Houston, Hope Richards is seen in recovery after surgery to separate her from her conjoined twin Anna. The two toddler girls The girls who were born in 2016 conjoined at the chest and abdomen. The successful surgery was announced Monday, Feb. 12, 2018. (Paul Vincent Kuntz/Texas Children's Hospital via AP)

  • In this Jan. 13, 2018, photo provided by Texas Children's Hospital in Houston, Jill and Michael Richards check on their daughter, Anna, in recovery following surgery to separate her from her conjoined twin, Hope. The two toddlers were born in 2016 conjoined at the chest and abdomen. The hospital announced the successful surgery Monday, Feb. 12, 2018. (Paul Vincent Kuntz/Texas Children's Hospital via AP)

  • In this Jan. 13, 2018, photo provided by Texas Children's Hospital in Houston, Jill and Michael Richards along with their two sons, Collin and Seth, stand in the recovery room by the two beds after their twin conjoined daughters, Anna and Hope Richards, were successfully separated. The two girls were born in 2016 conjoined at the chest and abdomen. The successful surgery was announced Monday, Feb. 12, 2018. (Paul Vincent Kuntz/Texas Children's Hospital via AP)

© 2018 The Associated Press. All rights reserved.