One thing we can rely on not thinking about while pregnant is that at least we can’t get pregnant again right now... right?
There is an exceedingly rare phenomenon called superfetation in which a woman can become pregnant with a new embryo while she is already pregnant with another one. It is so rare in fact that there are only 10 documented cases of it occurring in humans.
In other words a woman is pregnant with two babies, but they are not twins—one is older than the other, usually by a few weeks.
Don’t worry, your high school biology teacher did not mislead you. Normally when a woman becomes pregnant, the hormonal shift that occurs in her body stops ovulation (the release of another egg), which is why you stop getting your period when you are pregnant.
In the case of superfetation, however, for reasons not well understood, a woman does ovulate again after conceiving the first baby. And if she has sex during that fertile window, she can conceive again.
This unexpected turn of events recently became Jessica Allen’s reality. Ms. Allen decided to be a surrogate for a family, and through IVF became pregnant. At a routine ultrasound several weeks later, doctors told her she was actually carrying two babies.
Both families went through the pregnancy thinking she was pregnant with twins. However shortly after they were born, both families started to notice that the babies looked quite different from each other. DNA tests were done and to everyone’s shock, one of the babies matched the DNA of the legal parents, and the other matched the DNA of the surrogate.
After lengthy and costly legal proceedings, Ms. Allen and her husband obtained legal custody of their son.
Ms. Allen recently told the New York Post, "I don’t regret becoming a surrogate mom because that would mean regretting my son. I just hope other women considering surrogacy can learn from my story. And that a greater good will come out of this nightmare."
As for you, don’t spend too much time worrying that this will happen to you (although if you’re intrigued and kind of into the idea, thats okay too). And even if it does, it’s still very possible to have a healthy pregnancy with healthy babies—and a very interesting story to tell.