Most women suffer morning sickness during their pregnancies, but about 2% of them require hospitalization for an extreme version known as hyperemesis. A study published last week in the journal Nature narrows down the cause to a single hormone called GDF15.
The study’s lead author is Dr. Marlena Fejzo, a geneticist and professor at USC’s Keck School of Medicine. Fejzo experienced hyperemesis during her second pregnancy in 1999.
“My second pregnancy was so severe that I could not eat, drink, or move without violently vomiting for weeks and weeks,” Fezjo explains.
She describes the bout as torture. Initially, her doctor said she was trying to get attention from her husband and parents. By the time she was bedridden, Fejzo says humiliation took hold — her parents ended up changing her bedpan.
To treat the symptoms, she was initially placed on an IV. But the condition was so intense that her baby died.
“Nothing worked, and I ended up being put on a feeding tube. And the nutrition that I was given, the parenteral nutrition, was given too late.”
After her recovery, Fejzo says she decided to devote the rest of her life to figure out what happened to her. The National Institutes of Health denied her application for funding, and eventually turned to the biotech company 23andMe for her research. There, she was able to survey consenting customers with the company, as well as conduct genetic studies.
At that point, she discovered the risk factor for hyperemesis was the common nausea and vomiting hormone known as GDF15. Men and women make the hormone, Fejzo says, and it’s often produced when the body’s in a weakened state.
“If you have a virus or you have a bacterial infection or you have cancer, those organs are going to produce GDF15. It's a way to tell the body that you are in a weakened condition, you should rest and recover and not go out searching for food.”
During pregnancy, however, the fetal parts of the placenta produce high levels of the hormone. Fejzo says it’s the way the body tells itself to rest as the baby develops and to avoid certain foods that could be dangerous to the child bearer. Typically, it goes away during the second and third trimesters.
Through her research, Fejzo found that some people not only have a predisposition for lower levels of the hormone, but a fetus’ genes also play a role.
“If the fetus produces higher levels through the placenta during pregnancy, it's that balance between the lower levels before that give you an increased sensitivity to the higher levels during pregnancy. So it can vary from pregnancy to pregnancy, because the levels of GDF15 during pregnancy are primarily driven by the genetics of the fetus.”
There are still unanswered questions and theories swirling over what determines a fetus’ GDF15 levels.
“We already know that female fetuses produce more than males, which is probably why it's slightly more common to have nausea and vomiting [during] pregnancy and more severe symptoms when you're carrying a female. We suspect that there are genetic changes that can occur, possibly from inheriting overexpressing GDF15 genes from the father in some cases. But we don't totally have the answers to other ways that it can be increased in the fetus, yet we just have theories.”
She continues, “One theory is that we know that the placenta is an organ that divides very quickly, and it makes a lot of genetic mistakes. And so it could be possibly, in some cases, a triplication or a quadruplication of this gene. But the main factor does appear to be the genetic predisposition of the mother.”
People of African ancestry are also more prone to hospitalization for hyperemesis, Fejzo says.
So what can be done to treat it? Fejzo says so far, there are two options:
“We showed in this study that in mice, you can give the mice a high level of this hormone, and they will lose their appetite and lose weight. … But if you give them a low level prior to that high level, you can actually desensitize them or prime them, somewhat similar to what we do with allergies to desensitize people to certain allergens. That is a really exciting approach to prevent hyperemesis in pregnancy. And then we have the other approach, which is to treat it during pregnancy with drugs that block this hormone.”
Meanwhile, Fejzo is aware that people from all over the world, including the United States, are still being brushed off by medical professionals.
“Shockingly, we received a recording of a doctor that is still teaching her medical students that people with hyperemesis — that are hospitalized — it's usually because there's something going on at home or they just don't want to get better. So those are the exact words that she taught her medical students. And so we've got a new generation that's being sold this misogynistic nonsense. And so it gets perpetuated generation after generation. And doctors don't really have time to read journals like Nature, so they may not hear about these results.”