This Is the Worst Thing You Ever Did to Your Mother

The state of the universe.
May 11 2014 8:45 AM

The Worst Thing You Ever Did to Your Mother

An apology for all the manipulation, invasion, and theft.

Fetus and placenta.
Fetus and placenta. Also known as invader and siege engine.

Photo courtesy Wei Hsu and Shang-Yi Chiu/Creative Commons

Mother’s Day is a day of appreciation, of gratitude, and of guilt. Guilt for all the things I put my mother through over the years. A time to say I’m sorry, and to recognize how much she did for me. This Mother’s Day I’d like to apologize for what is probably the worst thing I’ve ever done to my mother. And you did it to your mother, too.

Dear Mom: I’d like to say I’m sorry. I’m sorry for manipulating you, stealing from you, taking control of your blood supply, and consuming part of your body. I, like everyone else alive today, did all this before I was even born, with an organ I no longer possess. Of course, I wasn’t consciously doing these things to you, in the same way I’m not consciously controlling my liver. It just sort of happened.

It all started when I was a zygote. I was floating through your uterus when I bumped into your uterine wall. I’m not proud of what I did next, but I really wasn’t thinking. (That’s not an excuse—I was just a clump of cells.) I used my outer layer of cells to invade and destroy parts of your uterus. This outer layer consisted of my trophoblast cells, and I used them like a horde of ravenous snakes: winding through your uterine wall, killing your cells, and sucking up your nutrients. With my trophoblasts I burrowed into your uterine wall like a parasite until I was completely embedded in your tissue.


Then I went a little psycho on you. In good embryo fashion, my trophoblasts grew into clumps that fused with your blood vessels. I grew hollow spaces within these clumps, and these spaces filled with your blood. Together, all these blood-filled spaces became my placenta, one of the strangest organs on Earth. The blood inside these clumps was all yours, but the tissue that surrounded them was grown from my cells. Because your blood vessels fused with my trophoblast clumps to create these blood chambers, my placenta was a hybrid organ made from both of us. (We shared an organ together—attachment and bonding!) I then grew wriggly little projections into these blood chambers. These projections were filled with blood vessels from my umbilical cord that let me pass my waste into your bloodstream and soak up oxygen and nutrients from your body.

Just when you thought I couldn't get any more demanding, I started actively invading your blood supply. This is where humans are especially destructive. No other animal is so ruthless in its invasion. For most animal species, Mom’s blood vessels remain safely hers, but humans are not like most animals. My cells began surrounding the arteries you used to fill my placenta with blood. These arteries provided your blood to the chambers of my placenta, and thus provided me with much-needed oxygen and nutrients. Slowly my cells began to replace your artery walls, effectively taking your placental arteries under my control. Once I had control of your arteries, I widened them to increase the amount of blood that entered the blood chambers, which increased the amount of oxygen and nutrients passing through my placenta (and thus to me). But that was just small-scale control—I wasn’t done yet.

This is where I feel really bad. This is where things get dangerous. My placenta started secreting hormones that lowered your blood pressure and increased your blood sugar. At the least, this probably made you lightheaded. At worst, this could have killed us both. You could have developed gestational diabetes, which would have shot your blood sugar dangerously high. We’re incredibly lucky we made it through. But of course at the time I wasn’t concerned with these things. I was just making sure there was enough sugar and oxygen coming to me, me, me. I was a growing fetus, after all. And here you thought I was demanding after I was born!

Anyway, I guess what I’m trying to say is thank you. Thank you for letting me grow inside you, kill your cells, take your nutrients, and control your hormones. Thank you for tolerating all this while also making sure I survived and came out healthy and happy. In short, thanks for being my mom. Happy Mother’s Day.

Rebecca R. Helm is a Ph.D. candidate at Brown University, where she studies evolution and developmental biology. She blogs at



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