Aetiology
The aetiology of NVP remains largely unknown. Most evidence supports the theory that elevated hormone levels are responsible for NVP. Progesterone has been shown to decrease gastric motility and cause nausea and vomiting in non-pregnant women.[3] Some studies have shown that NVP is associated with elevated human chorionic gonadotrophin levels.[4] While several studies have demonstrated a possible connection between oestrogen levels and NVP, a review of 17 studies demonstrated no relationship in 12 of the studies.[5][6] One systematic review demonstrated an association between the presence of Helicobacter pylori and hyperemesis gravidarum.[7]
Pathophysiology
The underlying pathophysiology of NVP is unclear, although it is understood that decreased gastric motility may play a role.[8]
Classification
Clinical classification[1]
No formal classification for NVP exists. However, in clinical practice it is useful to consider NVP as:
without volume depletion
with volume depletion and electrolyte imbalance
with persistent vomiting, volume depletion and electrolyte imbalance, ketosis, and >5% weight loss (hyperemesis gravidarum).
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