Dear Doctors: My husband and I are ready to expand our family, but I had such bad morning sickness for my whole pregnancy last time that I'm scared. Can you please talk about recent news about what causes morning sickness and if this may lead to a treatment that actually helps?
Dear Reader: "Morning sickness" is a general term that refers to the unpleasant, and sometimes debilitating, sensations of nausea that can occur during pregnancy. Research suggests that between 70% and 80% of women experience some degree of morning sickness while they are pregnant. The intensity ranges from mild queasiness, akin to feeling carsick, to powerful nausea that leads to vomiting. Despite its name, morning sickness can occur at any time of the day or night. The duration of this type of nausea varies greatly, as well. Although associated with the first trimester of pregnancy, morning sickness can continue well beyond that.
For an estimated 2% of pregnant women, the nausea and vomiting become quite severe. This is a condition known as hyperemesis gravidarum. It can cause dehydration, weight loss and malnourishment and lead to long-term health problems for both the mother and the baby. These include an increased risk of developing blood clots, dangerously high blood pressure, miscarriage or premature birth. In some cases, the condition can require hospitalization, and can even result in maternal death.
When it comes to what causes morning sickness, the answer has been a general one: It is related to hormones. Now, an international team of researchers from the United States, United Kingdom and Sri Lanka has identified a specific hormone as the catalyst for the distress. Known as growth/differentiation factor 15, or GDF15, it plays a role in several physiological pathways in the body. Among these is suppressing appetite, which has led to it being proposed as a treatment for obesity. The hormone is present throughout the body in low levels. But during pregnancy, the tissues of the placenta produce it in abundance.
Some fortunate women have no response to this increase in levels of GDF15. But for those with a sensitivity to the hormone, morning sickness is the result. The researchers found that both tolerance to GDF15 and a heightened sensitivity to the protein are linked to genetic factors. In a fascinating twist, when the fetus carries certain genetic mutations that the mother does not, it can affect how her body responds to GDF15. This sheds light on the perplexing question of why a woman may experience morning sickness in some, but not all, of her pregnancies.
The good news is that this discovery points to potential treatment avenues for both morning sickness and hyperemesis gravidarum. One approach is developing medications that would suppress production of GDF15 or decrease or inactivate it. Researchers have also proposed the development of a treatment that would gradually expose a woman to the hormone prior to a planned pregnancy, and thus desensitize her to its effects.
As more is learned about the genomic aspects of GDF15 and morning sickness, genetic testing may someday also have a role.
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