Master Class

Nausea and Vomiting in Pregnancy


Nausea and vomiting are common in pregnancy and can have a significant negative effect on women's health. Approximately half of all pregnant women in the United States have nausea and vomiting in early pregnancy, and about 25% have nausea alone. Only about 25% of pregnant women are free of any such problem.

The problem presents across a broad spectrum of severity, with the most severe form being hyperemesis gravidarum, a condition characterized by persistent vomiting, weight loss greater than 5%, ketonuria, electrolyte abnormalities, hypokalemia, and dehydration; this condition usually results in the need for hospitalization, treatment with intravenous fluids, and even intravenous feeding. Approximately 1% of pregnant women have vomiting severe enough to require hospitalization.

Persistent mild nausea, however, can also be a significant problem worthy of attentive management. It is not just “morning sickness” for many of these women. Approximately 35% of women with nausea during pregnancy lose time from work, and 25% cannot function well at home throughout the day.

Nausea and vomiting can significantly impair their routines, can negatively affect their relationships with their husbands and children, and are sometimes cited as reasons for an otherwise undesired pregnancy termination.

Women who are suffering from nausea and vomiting in pregnancy frequently do not seek or receive specific therapy out of concern over safety, yet such fear is often based on misinformation and misperceptions regarding teratogenesis. Women have numerous safe and effective options, including therapy with vitamin B6 and doxylamine, as well as ginger and other nonpharmacologic approaches, and treatment with various antiemetic drugs.

Etiology, Differential Diagnosis

Some patients can identify the triggers of their nausea and thus can avoid aggravating odors or foods. Dietary modifications include eating frequent and small meals; taking fluids between meals; eating primarily bland, dry, and high-protein foods; and avoiding fatty or spicy foods.

Discontinuing prenatal vitamin tablets containing iron also can help, as the iron can contribute to nausea. Women who are having trouble can switch to a multivitamin with no or low iron for the first trimester and can resume prenatal vitamins after 3 months, or they can switch to folic acid alone, which is all that is needed to prevent birth defects.

We must also consider other diagnoses that can cause nausea and vomiting in pregnancy, from gastroenteritis, pancreatitis, appendicitis, and other gastrointestinal disorders, to gastrourologic problems such as pyelonephritis and various metabolic disorders.

There are sometimes clues that the nausea and vomiting cannot be attributed to the pregnancy alone: Fever, abdominal pain, and headache, for instance, result from something other than the pregnancy, as do serious changes in liver enzymes, bilirubin, and amylase or lipase.

Nausea and vomiting that begin later in the pregnancy also cannot be attributed to the pregnancy itself. The problem has an early onset, usually starting at the time of the missed menstrual period. It is fully manifested by 10 weeks of gestation, and—although it usually improves as the pregnancy progresses further—the problem may persist until the placenta is delivered.

In any case, a patient who has not had any nausea in the first 3 months of her pregnancy and begins experiencing nausea and headache at 16 weeks of gestation is probably having a migraine headache.

Many believe that nausea and vomiting are related to the presence of human chorionic gonadotropin (HCG), because HCG can stimulate the ovaries to produce estrogen, and estrogen can contribute to nausea. Indeed, the start, peak, and resolution of nausea and vomiting in pregnancy correlate closely with the curve of HCG concentration. Nausea and vomiting are also more common in patients with multiple gestations and hydatidiform moles, obstetric situations in which HCG is high.

Hormonal influences do not explain, however, why some women have problems with nausea and others do not.

Over the years, some have believed that the problem is psychological, but I and many others strongly discount this belief. Any psychological problems these women have are not a cause of their nausea and vomiting, but rather are an effect.

Gastrointestinal dysmotility and Helicobacter pylori infection have been cited as other possible associations. H. pylori seropositivity has been associated with hyperemesis or serious nausea and vomiting, but data are conflicting and investigators have not studied whether the problem resolves after treatment for the infection. Ulcer disease should register as a possibility in any differential diagnosis, particularly if the woman has pain, but whether it is more broadly causative of the nausea and vomiting of pregnancy is uncertain.

There is also some evidence that the nausea and vomiting of pregnancy may be related to vitamin B6 deficiency, and indeed, a significant number of women respond to vitamin B6 supplementation. Overall, however, the etiology of nausea and vomiting in pregnancy are unknown.


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