In a rare medical event, a Californian surrogate mother became pregnant with her own child during the surrogate pregnancy—and only found out the second child was hers after their birth.
The surrogate mother, Jessica Allen, was matched with a couple, and after two rounds of in-vitro fertilization, Allen became pregnant with the couple's embryo in April 2016.
However, during an ultrasound six weeks into the pregnancy, Allen's doctor noticed a second fetus, Allen said. The assumption was that Allen was pregnant with identical twins. Allen recalled, "[The doctor] started moving the ultrasound around and he goes, 'Well I definitely see that there is another baby.'" Allen added, "The chance of an embryo splitting is very small, but it does happen, and I just thought ... I was very surprised."
The pregnancy continued, and Allen eventually delivered what she thought was a set of identical twin boys via cesarean section. Allen said was not able to see the newborns in person, although she said she noticed they looked different from each other when she briefly saw a cellphone picture of the infants.
However, about a month after the delivery, the biological mother of the surrogate child contacted Allen, voicing concern that the second child did not resemble her, the father, or the other child. Subsequent DNA testing determined that the one child was the biological son of Allen and her husband—and not the surrogate parents.
After what turned into "lengthy, expensive legal battle," Allen was able to reunite with her biological child, Malachi, according to the Washington Post's "To Your Health." Allen added, "I carried my own child. I didn't know he was mine."
How the second pregnancy occurred—a bit a medical mystery
According to Jennifer Ashton, a physician and ABC News' chief medical contributor, the phenomenon process of a woman becoming pregnant with a second fetus while already pregnant—known as superfetation—is extremely rare. Karen Boyle, a reproductive medicine specialist, said there are only 10 documented cases in medical literature.
Superfetation occurs when a woman continues to ovulate once pregnant, potentially resulting in two fetuses at different gestational ages and—in Allen's case—with two different sets of parents. According to Ashton, superfetation can occur both in natural pregnancies and in-vitro fertilization. Ashton said there is no good hormonal or physiological explanation for the phenomenon.
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