What causes HG?

Without a doubt, one of the biggest questions we get at Hyperemesis Australia, and one that we have ourselves asked too many times to count is ‘what in the hell causes HG?’

The truth is, we don’t yet have a definitive answer to this question. It’s heartbreaking and confusing and we hate that we can’t tell you - because if we knew what caused it we’d be that much closer to curing it. 

Our American sister organisation, The HER Foundation, are the leaders in research on this topic. According to their website, there are numerous theories regarding the cause of HG; however, none are, as of yet, conclusive. A cause is very difficult to determine and is most likely not due to only one factor. It may vary between women depending on biological make-up (genetics), body chemistry, and overall health. 

They go on to say that most of the current theories centre around known pregnancy-related factors like hormonal changes (e.g. estrogen increase) and physical changes (e.g. relaxed esophageal sphincter) since the onset is related to pregnancy and ends before or at delivery. Research is limited and minimal funding is granted for hyperemesis research, so high-quality studies with decisive results are uncommon. If you’d like to read more about the existing research here is a list of links from HER. 

• Human Chorionic Gonadotropin (hCG) & Estrogen Hormones
  Most theories centre around the increase in hCG & estrogen hormones like progesterone in early pregnancy

• Psychological Causes
  Some mistakenly state psychological causes, but most if not all women experience psychological effects (e.g.: frustration, feelings of helplessness, isolation, depression, etc.) secondary to HG

• Thyroxine Levels
  Increase in serum thyroxine levels have been documented in 70% of pregnancies complicated by HG

• Gastric Neuromuscular Dysfunctions
  A recent theory cites a dysfunction that results in regurgitation of duodenal content back into the stomach and subsequent nausea and vomiting

• Deficiencies of Nutrients
  Another theory attributes HG to deficiencies of pyridoxine and zinc, though results are not conclusive

• Other Theories & Resource Links
  Links & abstracts to various other physiological and immunological theories

There are also studies being conducted that suggest the placenta and appetite genes GDF15 and IGFBP7 are associated with hyperemesis gravidarum. For more information read this piece by our UK sister organisation Pregnancy Sickness Support.