Sept. 25, 2009 -- The media have been buzzing with reports of a pregnant woman in Arkansas getting pregnant again, with her babies conceived two and a half weeks apart.
Her case might be a rare example of "superfetation," in which a pregnant woman ovulates and winds up with a second pregnancy.
But the key word there is "might." It's not certain that Todd and Julia Grovenburg of Fort Smith, Ark., have a superfetation pregnancy.
The Arkansas TV station that interviewed the Grovenburgs posted a statement from Julia Grovenburg's doctor, who confirms that Grovenburg is pregnant with twins and "there appears to be a discordant growth pattern, possibly due to superfetation."
Her doctor, identified as M. Muyalert, MD, says that superfetation is "an unusual and rare condition, but the possibility is real."
But Muyalert cannot confirm superfetation, stating only that there is a "suspicion of superfetation" in the Grovenburgs' case.
Jeffrey Kuller, MD, professor of obstetrics and gynecology at Duke University Medical Center, tells WebMD that based on the media reports he's seen, he's "skeptical" that the Grovenburg pregnancy is a case of superfetation.
"It's possible that this has occurred, but it's certainly not for certain," Kuller says.
Kuller says obstetrical textbooks mention a handful of reported cases of superfetation, but it's "extremely uncommon" and is biologically "unlikely," although not implausible.
"We occasionally see a patient like this, where you'll see a discrepancy between the twin weights and growth, and oftentimes, the more likely explanation is just that one is lagging in growth or one has a problem, like a chromosomal abnormality, that makes it smaller than the other one," Kuller says.
It's possible that the Grovenburgs' second baby wasn't discovered earlier during the pregnancy, notes Kuller, who says he had a patient with a suspected case of superfetation several years ago but no certain cases of superfetation.
One of the challenges of a superfetation pregnancy would be timing the delivery of the babies, Kuller says.
"If you truly believed it was a superfetation pregnancy, you would have to decide the best time for both of the babies to be delivered," he says, noting that twins are usually delivered at 38 weeks.
But what if one baby was conceived a couple of weeks ahead of the other one? Then it's a matter of finding a compromise delivery date that would be best for both babies, "so that one didn't go post-term and the other preterm," Kuller says.
"But again," Kuller says, "this would be such a rare event that there would be no way to say, based on the last 10 we did ... or based on the literature, this is how you should follow such a pregnancy."
In the couple's interview with Arkansas TV station KFSM, Julie Grovenburg says the babies, Jillian and Hudson, appear "perfectly healthy" and are due in early December. She says that to prove superfetation "without a shadow of a doubt, would have to be something that was done after the babies are born."
But doctors may never be able to tell the Grovenburgs for sure if their babies came from a superfetation pregnancy.
"I don't think there would be a definitive way to do that," Kuller says. "I think it would still be speculative."