Pathophysiology
It was previously thought that circulating hCG levels were responsible for the majority of symptoms. GI tract smooth muscle relaxation was also believed to contribute to symptoms of reflux.
The most recent research suggests that the primary cause of NVP is hypersensitivity to the vomiting hormone growth differentiation factor 15 (GDF15).6 GDF15 is produced through the activation of placental genes, resulting in a rise in circulating levels in the first half of pregnancy. GDF15 has been shown to act on the hindbrain directly triggering nausea and vomiting. Patients who go on to develop HG have been found to have particularly elevated levels of GDF15, with those who had low pre-pregnancy levels of the hormone at particular risk of symptoms.
Learning Bite
Hypersensitivity to increased levels of GDF15 is currently believed to be the primary cause of NVP and HG.