It sounds biologically impossible — there’s no way you can get pregnant when you’re already pregnant, right? Wait, can you get pregnant when you’re already pregnant? We all learned in sex ed that once a woman is pregnant, her body stops releasing eggs. But everything we learned is a lie!

 

So can you get pregnant when you’re already pregnant?

Yes, it IS possible to get pregnant again while you’re already pregnant — but it’s incredibly rare. The occurrence of another pregnancy during an ongoing pregnancy is called superfetation. There’s a slew of improbable things that have to occur in order for this to happen.

The ovaries don’t get the memo

After a fertilized egg implants in a woman’s uterus, the body starts producing the hormone human chorionic gonadotropin (hCG), which signals to the ovaries to stop releasing eggs. In rare circumstances, the ovaries don’t register the hCG, so they continue to produce eggs.

Houdini-like sperm

When a woman becomes pregnant, her cervix closes to protect the uterus and the developing fetus. In superfetation, a sperm somehow manages to get past the closed cervix. Then it has to find and fertilize the second egg. That is some magical sperm!

The egg is determined

The fertilized egg has one final challenge — it somehow has to implant itself into the already inhabited uterine wall.

If all of these things occur, then a woman can find herself pregnant with two babies with different gestational ages. Superfetation is incredibly rare in humans— there are only about ten documented cases in the world.

Three known few superfetation cases have occurred in the last decade. In one, an Australian woman’s daughters were conceived ten days apart. In another case, an Arkansas woman conceived her son and daughter two weeks apart. And in the most amazing pregnancy, a woman in the UK conceived her son and daughter five weeks apart.

The risks in a superfetation pregnancy are similar to any twin pregnancy, with one exception — the younger baby will be born prematurely. And since twins are often delivered between 36 and 37 weeks gestation, that means one baby will be deprived of crucial development time. Luckily for the mother in the UK, her younger baby only needed two weeks in neonatal intensive care before she was released.

So, there you have it — guess technically you can get pregnant when you’re already pregnant. Yikes.

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(Image: iStock / Halfpoint)