Theories & Research
There are numerous theories regarding the etiology 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. However, as is common in poorly understood disorders, a psychological cause is named when a physiological one is not known.
This is especially true when so many of the symptoms like nausea are not objectively measurable. Thus it is easy to dismiss a woman's symptoms as being psychological, exaggerated, or imaginary, when in fact they are very real and may in fact be very severe. However, accurately determining severity is difficult, especially if there is not obvious "proof" of how sick a woman is. Proof, such as severe weight loss or dehydration, often comes after she is very sick for some time, and it is then more difficult to manage her symptoms.
Early Research & Perspectives
Hyperemesis gravidarum became a recognized disorder several centuries ago, but the first research appears to have been published in the 18th century. Incidence in the United States is reported to be about 60,000 cases annually; however, that number only reflects those treated as inpatients, not those treated at home or in outpatient/urgent care facilities. With the focus on cost reduction in health care, the majority of women are not admitted to the hospital. Thus the incidence of HG is likely several times greater than suggested. It is not actually a rare disorder. If it is not treated, a mother can suffer greatly and may even have acute or chronic anxiety and/or depression from the trauma of incessant nausea and vomiting.
HG was first thought to be related to a physiological cause such as toxins, ulcerations, or infection in a related organ. A physical cause such as abnormalities of the female reproductive system was also suggested. Early in the 20th century, a psychological cause was proposed by those subscribing to psychoanalytic theories. Unfortunately, despite the lack of evidence in these biased studies, their assumptions have persisted to this day. Every type of medical professional from pharmacist to nurse and allopathic to naturopathic physician is typically taught that HG is a psychological disorder. Many textbooks and published medical research still erroneously suggest that HG is psychosomatic, as well. It is no surprise that women suffering from HG are often left untreated or not taken seriously. This belief has been passed from generation to generation of health professional despite the multitude of evidence showing many contributing factors unrelated to psychological conflicts.
Currently, many theories are being tested, and new ones
emerge every year. Most center 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.
- Human Chorionic Gonadotropin (hCG)
& Estrogen Hormones
Most theories center around the increase in hCG & estrogen hormones like progesterone in early pregancy.
- 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 pregancies 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.
Updated on: Sep. 15, 2022
The Chronicles of Nausea
Beyond Morning Sickness