Severe Morning Sickness: What are the Myths, and How Important is Proper Prevention and Treatment?

Geneticist Marlena Fejzo and her colleagues have discovered that the most severe form of morning sickness, hyperemesis gravidarum (HG), is caused by the hormone GDF15 and not, as previously assumed, by human chorionic gonadotropin. In a peer-reviewed opinion piece published in the journal Trends in Molecular Medicine, Fejzo dispels common myths about morning sickness and discusses possible treatments, including sensitizing affected women to GDF15 before pregnancy, similar to the treatment of allergies. “HG can be life-threatening and is associated with serious consequences that must be taken seriously,” says Fejzo of the Keck School of Medicine at the University of Southern California. “Now that we know that GDF15 is the most likely cause of HG, we are close to developing treatments that target this hormone pathway and end the suffering.”

Myth 1: Severe Morning Sickness is Harmless and Normal

Pregnant women with hyperemesis gravidarum are essentially starving themselves, says Fejzo, and a growing body of research shows that this has serious short- and long-term clinical implications for both the parent and the child. HG is a significant predictor of postnatal depression, and 26% of pregnant women with HG report suicidal thoughts, while 18% meet all the criteria for post-traumatic stress disorder.

For the child, HG is associated with premature birth, low birth weight, and later in life with autism spectrum disorders, ADHD, depression, and social problems, as well as an increased risk of childhood cancers and respiratory and cardiovascular diseases. Nevertheless, pregnant women with this condition are often dismissed by their doctors and families. In extreme cases, those affected by HG can develop Wernicke’s encephalopathy, a life-threatening swelling of the brain due to a thymidine deficiency (vitamin B1). “I believe that all women with hyperemesis should receive vitamin B1 to prevent this severe brain swelling, which can lead to permanent brain damage and often to the death of the fetus,” says Fejzo.

Myth 2: Morning Sickness is Caused by Human Chorionic Gonadotropin (hCG) Or is Psychosomatic

Although it has long been assumed that morning sickness is caused by hCG, recent groundbreaking research has shown that the main cause of HG is actually the hormone GDF15, which is part of a normal stress response. Normally, GDF15 is secreted in very small amounts, but during early pregnancy, it rises sharply, then declines, and finally rises again in the third trimester. A study in Nature, co-authored by Fejzo, has shown that women suffering from HG may have genetic variants that cause them to have lower levels of GDF15 in their blood before pregnancy, making them particularly sensitive when they become pregnant and are suddenly exposed to high concentrations.

This finding has clinical implications for the prevention and treatment of HG, as preliminary research suggests that it may be safe to manipulate GDF15 during or even before pregnancy. “If we can increase GDF15 levels before pregnancy, it could lead to desensitization, similar to how we try to desensitize people with severe allergies to allergens,” says Fejzo. “And during pregnancy, we could potentially minimize or eliminate symptoms by blocking GDF15 or its receptors in the brain stem.”

Myth 3: Only Humans Suffer From Morning Sickness

Nausea and loss of appetite during pregnancy are not exclusively human traits—these symptoms have been observed throughout the animal kingdom, from monkeys, dogs, and cats to chickens, vipers, and squids. Fejzo suspects that pregnancy-induced nausea serves not only to prevent the ingestion of harmful foods, but also to discourage dangerous foraging. “This condition probably evolved because it was beneficial not to forage during pregnancy,” says Fejzo. “That may still be true for animals, but humans no longer need it, so we should end the suffering once and for all if we can.”