Hyperemesis gravidarum is a complication of pregnancy characterized by intractable nausea,
vomiting, and dehydration and is estimated to affect 0.5–2.0% of pregnant women. Malnutrition
and other serious complications, such as fluid or electrolyte imbalances, may result.
Hyperemesis is considered a rare complication of pregnancy, but because nausea and vomiting
during pregnancy exist on a spectrum, it is often difficult to distinguish this condition
from the more common form of nausea and vomiting experienced during pregnancy known as morning
sickness.
Signs and symptoms When hyperemesis gravidarum is severe or inadequately
treated, it may result in the following: Loss of 5% or more of pre-pregnancy body weight
Dehydration, causing ketosis, and constipation Nutritional disorders such as Vitamin B1 deficiency,
Vitamin B6 deficiency or Vitamin B12 deficiency Metabolic imbalances such as metabolic ketoacidosis
or thyrotoxicosis Physical and emotional stress of pregnancy
on the body Difficulty with activities of daily living
Symptoms can be aggravated by hunger, fatigue, prenatal vitamins, and diet. Some women with
hyperemesis gravidarum lose as much as 10% of their body weight. Many sufferers of HG
are extremely sensitive to odors in their environment; certain smells may exacerbate
symptoms. This is known as hyperolfaction. Ptyalism, or hypersalivation, is another symptom
experienced by some women suffering from HG. Hyperemesis gravidarum tends to occur in the
first trimester of pregnancy and lasts significantly longer than morning sickness. While most women
will experience near-complete relief of morning sickness symptoms near the beginning of their
second trimester, some sufferers of HG will experience severe symptoms until they give
birth to their baby, and sometimes even after giving birth.
Causes There are numerous theories regarding the
cause of HG, but the cause remains controversial. It is thought that HG is due to a combination
of factors which may vary between women and include: genetics, body chemistry, and overall
health. One factor is an adverse reaction to the hormonal
changes of pregnancy, in particular, elevated levels of beta human chorionic gonadotropin.
This theory would also explain why hyperemesis gravidarum is most frequently encountered
in the first trimester, as hCG levels are highest at that time and decline afterward.
Another postulated cause of HG is an increase in maternal levels of estrogens.
Pathophysiology
Although the pathophysiology of HG is poorly understood, the most commonly accepted theory
suggests that levels of hCG are associated with it. Leptin may also play a role.
Possible pathophysiological processes involved are summarized in the following table:
Diagnosis Hyperemesis gravidarum is considered a diagnosis
of exclusion. HG can be associated with serious maternal and fetal morbidity, such as Wernicke's
encephalopathy, coagulopathy, peripheral neuropathy, fetal growth restriction, and even maternal
and fetal death. Women experiencing hyperemesis gravidarum
often are dehydrated and lose weight despite efforts to eat. The onset of the nausea and
vomiting in hyperemesis gravidarum is typically before the twenty-second week of pregnancy.
Differential diagnosis Diagnoses to be ruled out include the following:
Investigations Common investigations include blood urea nitrogen
and electrolytes, liver function tests, urinalysis, and thyroid function tests. Hematological
investigations include hematocrit levels, which are usually raised in HG. An ultrasound
scan may be needed to know gestational status and to exclude molar or partial molar pregnancy.
Management Dry bland food and oral rehydration are first-line
treatments. Due to the potential for severe dehydration and other complications, HG is
treated as an emergency. If conservative dietary measures fail, more extensive treatment such
as the use of antiemetic medications and intravenous rehydration may be required. If oral nutrition
is insufficient, intravenous nutritional support may be needed. For women who require hospital
admission, thromboembolic stockings or low-molecular-weight heparin may be used as measures to prevent
the formation of a blood clot. Intravenous fluids
IV hydration often includes supplementation of electrolytes as persistent vomiting frequently
leads to a deficiency. Likewise, supplementation for lost thiamine must be considered to reduce
the risk of Wernicke's encephalopathy. A and B vitamins are depleted within two weeks,
so extended malnutrition indicates a need for evaluation and supplementation. In addition,
electrolyte levels should be monitored and supplemented; of particular concern are sodium
and potassium. After IV rehydration is completed, patients
in general progress to frequent small liquid or bland meals. After rehydration, treatment
focuses on managing symptoms to allow normal intake of food. However, cycles of hydration
and dehydration can occur, making continuing care necessary. Home care is available in
the form of a PICC line for hydration and nutrition. Home treatment is often less expensive
than long-term or repeated hospitalizations. Medications
A number of antiemetics are effective and safe in pregnancy including: pyridoxine/doxylamine,
antihistamines, and phenothiazines. With respect to effectiveness, it is unknown if one is
superior to another, and there is even limited evidence of significant effect at all of pharmacological
therapy in hyperemesis gravidarum. While pyridoxine/doxylamine, a combination
of vitamin B6 and doxylamine, is effective in nausea and vomiting of pregnancy, some
have questioned its effectiveness in HG. Ondansetron may be beneficial, however, there are some
concerns regarding an association with cleft palate, and there is little high quality data.
Metoclopramide is also used and relatively well tolerated. Evidence for the use of corticosteroids
is weak; there is some evidence that corticosteroid use in pregnant women may slightly increase
the risk of oral facial clefts in the infant and may suppress fetal adrenal activity. However,
hydrocortisone and prednisolone are inactivated in the placenta and may be used in the treatment
of hyperemesis gravidarum. Nutritional support
Women not responding to IV rehydration and medication may require nutritional support.
Patients might receive parenteral nutrition or enteral nutrition. There is only limited
evidence from trials to support the use of vitamin B6 to improve outcome. Hyperalimentation
may be necessary in certain cases to help maintain volume requirements and allow weight
gain. A physician might also prescribe Vitamin B1 and folic acid supplementation.
Alternative medicine Acupuncture has been found to be ineffective.
The use of ginger products may be helpful, but the evidence of effectiveness is limited
and not consistent, though two recent studies support ginger over placebo.
Complications Pregnant woman
If HG is inadequately treated, anemia, hyponatremia, Wernicke's encephalopathy, renal failure,
central pontine myelinolysis, coagulopathy, atrophy, Mallory-Weiss tears, hypoglycemia,
jaundice, malnutrition, pneumomediastinum, rhabdomyolysis, deconditioning, deep vein
thrombosis, pulmonary embolism, splenic avulsion, or vasospasms of cerebral arteries are possible
consequences. Depression is a common secondary complication of HG and emotional support can
be beneficial. Infant
The effects of HG on the fetus are mainly due to electrolyte imbalances caused by HG
in mother. Infants of women with severe hyperemesis who gain less than 7 kg during pregnancy
tend to be of lower birth weight, small for gestational age, and born before 37 weeks
gestation. In contrast, infants of women with hyperemesis who have a pregnancy weight gain
of more than 7 kg appear similar to infants from uncomplicated pregnancies. There is no
significant difference in the neonatal death rate in infants born to mothers with HG compared
to infants born to mothers who do not have HG.
Epidemiology Vomiting is a common condition affecting about
50% of pregnant women, with another 25% suffering from nausea. However, the incidence of HG
is only 0.3–1.5%. After preterm labor, hyperemesis gravidarum is the second most common reason
for hospital admission during the first half of pregnancy. Factors such as infection with
Helicobacter pylori, a rise in thyroid hormone production, low age, low body mass index prior
to pregnancy, multiple pregnancies, molar pregnancies, and a past history of hyperemesis
gravidarum have been associated with the development of HG.
History Thalidomide was prescribed for treatment of
HG in Europe until it was recognized that thalidomide is teratogenic and is a cause
of phocomelia in neonates. Etymology
Hyperemesis gravidarum is from the Greek hyper-, meaning excessive, and emesis, meaning vomiting,
and the Latin gravidarum, the feminine genitive plural form of an adjective, here used as
a noun, meaning "pregnant [woman]". Therefore, hyperemesis gravidarum means "excessive vomiting
of pregnant women". Notable cases
Author Charlotte Brontë is often thought to have suffered from hyperemesis gravidarum.
She died in 1855 while four months pregnant, having been afflicted by intractable nausea
and vomiting throughout her pregnancy, and was unable to tolerate food or even water.
Catherine, Duchess of Cambridge was hospitalized due to hyperemesis gravidarum during her first
pregnancy. References