Sick from Pregnancy? A Protein in Your Placenta Could Be to Blame

A single protein might explain why some women have morning sickness during pregnancy while others come through the initial months without feeling much of anything.

According to a study done by researchers at the University of Cambridge, women who reported vomiting into their second trimester—when bouts of morning sickness will typically start to diminish—had higher concentrations of a protein called GDF15 in their blood around the start of their second trimester. The study involved about 2,229 women who were seen over eight years at one clinic.

The study was posted online on November 17 on bioRxiv, a website that allows researchers to share scientific papers before they go through peer-review, a process intended to serve as a quality-control measure for many journals. New Scientist first reported on the finding on Thursday.

This research isn’t the first time that GDF15 protein has been linked with pregnancy. A lack of this particular protein has previously been tied to miscarriages. Given that link, the authors of the new paper speculate that high levels of GDF15 could mean the placenta has developed properly (the opposite of what a deficiency indicates). As for why the protein is implicated in morning sickness, the authors theorize that perhaps the protein triggers vomiting during the early stages of pregnancy so women aren’t tempted to eat anything that might hurt the developing fetus.

Ukraine baby A Ukranian woman named only as Olga, plays with her new-born baby at the maternity hospital in the eastern Ukrainian city of Avdiivka on January 16, 2017. ALEKSEY FILIPPOV/AFP/Getty Images

The actual cause of morning sickness is still a mystery, according to the Clinical Evidence Handbook, published by BMJ. Another placental protein, human chorionic gonadotropin, may also be responsible. Some researchers think there may be a genetic link; if a woman’s mother had bad morning sickness, then she might, too.

If scientists can figure out exactly what is causing morning sickness, targeting GDF15 or other proteins that it affects could lead to new treatments. To accomplish that feat, more studies are needed in order to figure out exactly what controls GDF15 levels during development. Though one company is working on a drug to block GDF15 as a treatment for a particular wasting disease associated with cancer, it’s too soon to tell if that drug will be safe or effective in humans.

More research should also be done to see if the association between GDF15 and likelihood of vomiting exists among pregnant women who suffer from a more serious form of morning sickness known as hyperemesis gravidarum, the authors noted. Women who suffer from hyperemesis gravidarum can lose weight and dehydrate themselves from vomiting so much.

Incidentally, one myth around morning sickness—that it can predict the baby's gender—may be true: researchers noted that carrying a girl was also associated with morning sickness lasting into the second trimester.