Woman is pregnant with two babies, not twins: rare case of superfetation, say docs

A pregnant woman in Arkansas got shocking news when she went in for a routine ultrasound - she's pregnant again.

Next to Todd and Julia Grovenburg's growing baby girl, Jillian, doctors discovered a smaller male fetus who may have been conceived about two and a half weeks after Jillian, according to an ABC News report.

The Grovenburg babies may be a rare case of superfetation, or conceiving while pregnant, doctors said.

"When the woman had her ultrasound initially, they saw one sack, one baby developing, and that baby had a certain gestational age; then they noticed a second heartbeat in a child that was much, much younger developmentally," Dr. Karen Boyle of the Greater Baltimore Medical Center, told ABC News' "Good Morning America Health."

"It does really sound like this is a true case of different conception times for these children," Boyle continued, adding that she could only find "about 10 reported cases" of superfetation.

Grovenburg's obstetrician confirmed the surprising news to Arkansas' KFSM-TV.

"Mrs. Julia Grovenburg is pregnant with twins and there appears to be a discordant growth pattern, possibly due to superfetation," Dr. Michael Muylaert wrote in a letter to the station.

"This is an unusual and rare condition, but the possibility is real. It can only be confirmed after delivery by chromosomal and metabolic studies on the babies."

Boyle told ABC News that superfetation is often dangerous for the younger baby, who could be born prematurely, thus risking lung development problems. But in the Grovenburgs' case, a difference of two weeks would not present many risks.

"The interesting thing in this case is if these children were actually born on their due dates, the older child would be born at the end of 2009, and the younger child would be born in the beginning of 2010," Boyle said.