Morning sickness has been considered a condition with no known actual cause, but not anymore, according to the New York Times.
Scientists wondered about why we didn’t know more about what actually causes this condition. With millions of data being acquired annually, it seemed as if the cause was about to be discovered, but it wasn’t.
The so-called morning sickness affects as many as 4 our of 5 women. Until recently, researchers had only vague hypotheses to explain it, but recent studies point to a possible cause and could even open new possibilities to treatment.
Nausea and vomiting are most common in the first trimester but can last until the baby is born, ranging from mild nausea to its most severe form: hyperemesis gravidarum, characterized by relentless vomiting that can lead to malnutrition, weight loss and electrolyte imbalance that endanger the health of both the mother and fetus. Hyperemesis gravidarum is one of the most common reasons for hospitalization in pregnancy, second only to preterm labor, and occurs in somewhere between 0.3 and 3 pregnancies.
Marlena Fejzo, a geneticist at U.C.L.A. and the University of Southern California who studies hyperemesis gravidarum, had a severe form of the condition and despite multiple medications, IV fluids and a feeding tube, miscarried at the beginning of the second trimester. One specific study led by Dr. Fejzo showed that hyperemesis runs in families, with sisters of women with the condition having a 17-fold increased risk of experiencing it themselves. Less severe nausea and vomiting has also been shown to be strongly heritable.
These recent discoveries also fit in with an existing hypothesis that nausea and vomiting during pregnancy may actually be part of an evolutionary strategy to protect developing fetuses by reducing the chance that their mothers will consume foods containing toxins or pathogens during a critical time of organ development. “Maybe it’s an evolutionary trade-off that we keep a very, very low-risk diet in the first trimester of pregnancy,” said Dr. Stephen O’Rahilly.