Nausea and Vomiting During Early Pregnancy: A Merck Manual of Patient Symptoms podcast

Nausea and vomiting affect up to 80% of pregnant women. Symptoms are most common and most severe during the 1st trimester. Although common usage refers to morning sickness, nausea, vomiting, or both typically may occur at any point during the day. Symptoms vary from mild to severe (hyperemesis gravidarum).

Hyperemesis gravidarum is persistent, severe pregnancy-induced vomiting that causes significant dehydration, often with electrolyte abnormalities, ketosis, and weight loss (see Abnormalities of Pregnancy: Hyperemesis Gravidarum).

Pathophysiology

The pathophysiology of nausea and vomiting during early pregnancy is unknown, although metabolic, endocrine, GI, and psychologic factors probably all play a role. Estrogen may contribute because estrogen levels are elevated in patients with hyperemesis gravidarum.

Etiology

The most common causes of uncomplicated nausea and vomiting during early pregnancy (see Table 3: Symptoms During Pregnancy: Some Causes of Nausea and Vomiting During Early Pregnancy) are

• Morning sickness (most common)
• Hyperemesis gravidarum
• Gastroenteritis

Occasionally, prenatal vitamin preparations with iron cause nausea. Rarely, severe, persistent vomiting results from a hydatidiform mole.

Vomiting can also result from many nonobstetric disorders. Common causes of acute abdomen (eg, appendicitis, cholecystitis) may occur during pregnancy and may be accompanied by vomiting, but the chief complaint is typically pain rather than vomiting. Similarly, some CNS disorders (eg, migraine, CNS hemorrhage, increased intracranial pressure) may be accompanied by vomiting, but headache or other neurologic symptoms are typically the chief complaint.

Table 3
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Some Causes of Nausea and Vomiting During Early Pregnancy Cause Suggestive Findings Diagnostic Approach Obstetric Morning sickness (uncomplicated nausea and vomiting) Mild, intermittent symptoms at varying times throughout the day, primarily during the 1st trimester Normal vital signs and physical examination Diagnosis of exclusion Hyperemesis gravidarum Frequent, persistent nausea and vomiting with inability to maintain adequate oral intake of fluids, food, or both Usually, signs of dehydration (eg, tachycardia, dry mouth, thirst), weight loss Urine ketones, serum electrolytes, Mg, BUN, creatinine If the condition persists, possibly liver function tests, pelvic ultrasonography Hydatidiform mole Larger-than-expected uterine size, absent fetal heart sounds and movement Sometimes elevated BP, vaginal bleeding, grapelike tissue from the cervix BP measurement, quantitative hCG, pelvic ultrasonography, biopsy Nonobstetric Gastroenteritis Acute, not chronic; usually accompanied by diarrhea Normal (benign) abdomen (soft, nontender, not distended) Clinical evaluation Bowel obstruction Acute, usually in patients who have had abdominal surgery Colicky pain, with obstipation and distended, tympanitic abdomen May be caused by or occur in patients with appendicitis Abdominal imaging with flat and upright x-rays, ultrasonography, and possibly CT (if x-ray and ultrasound results are equivocal) UTI or pyelonephritis Urinary frequency, urgency, or hesitancy, with or without flank pain and fever Urinalysis and culture hCG = human chorionic gonadotropin.

Evaluation

Evaluation aims to exclude serious or life-threatening causes of nausea and vomiting. Morning sickness (uncomplicated nausea and vomiting) and hyperemesis gravidarum are diagnoses of exclusion.

History

History of present illness should particularly note the following:

• Onset and duration of vomiting
• Exacerbating and relieving factors
• Type (eg, bloody, watery, bilious) and amount of emesis
• Frequency (intermittent or persistent)

Important associated symptoms include diarrhea, constipation, and abdominal pain. If pain is present, the location, radiation, and severity should be queried. The examiner should also ask what social effects the symptoms have had on the patient and her family (eg, whether she is able to work or to care for her children).

Review of systems should seek symptoms of nonobstetric causes of nausea and vomiting, including fever or chills, particularly if accompanied by flank pain or voiding symptoms (UTI or pyelonephritis), and neurologic symptoms such as headache, weakness, focal deficits, and confusion (migraine or CNS hemorrhage).

Past medical history includes questions about morning sickness or hyperemesis in past pregnancies. Past surgical history should include questions about any prior abdominal surgery, which would predispose a patient to mechanical bowel obstruction.

Drugs taken by the patient are reviewed for drugs that could contribute (eg, iron-containing compounds, hormonal therapy) and for safety during pregnancy.

Physical examination

Examination begins with review of vital signs for fever, tachycardia, and abnormal BP (too low or too high).

A general assessment is done to look for signs of toxicity (eg, lethargy, confusion, agitation). A complete physical examination, including pelvic examination, is done to check for findings suggesting serious or potentially life-threatening causes of nausea and vomiting (see Table 4: Symptoms During Pregnancy: Relevant Physical Examination Findings in a Pregnant Patient With Vomiting).

Table 4
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Relevant Physical Examination Findings in a Pregnant Patient With Vomiting System Findings General Lethargy, agitation HEENT Dry mucosa, icteric sclera Neck Stiffness to passive flexion (meningismus) GI Distention with tympany Absent or high-pitched tinkling bowel sounds Focal tenderness Peritoneal signs (guarding, rigidity, rebound) GU Flank tenderness to percussion Uterus too large for dates Absent fetal heart sounds Grapelike tissue from the cervix Neurologic Confusion, photophobia, focal weakness, nystagmus HEENT = head, eyes, ears, nose, and throat.

Red flags

The following findings are of particular concern:

• Abdominal pain
• Signs of dehydration (eg, orthostatic hypotension, tachycardia)
• Fever
• Bloody or bilious emesis
• No fetal motion or heart sounds
• Abnormal neurologic examination
• Persistent or worsening symptoms

Interpretation of findings

Distinguishing pregnancy-related vomiting from vomiting due to other causes is important. Clinical manifestations help (see Table 3: Symptoms During Pregnancy: Some Causes of Nausea and Vomiting During Early Pregnancy).

Vomiting is less likely to be due to pregnancy if it begins after the 1st trimester or is accompanied by abdominal pain, diarrhea, or both. Abdominal tenderness may suggest acute abdomen. Meningismus, neurologic abnormalities, or both suggest a neurologic cause.

Vomiting is more likely to be due to pregnancy if it begins during the 1st trimester, it lasts or recurs over several days to weeks, abdominal pain is absent, and there are no symptoms or signs involving other organ systems.

If vomiting appears to be pregnancy-related and is severe (ie, frequent, prolonged, accompanied by dehydration), hyperemesis gravidarum and hydatidiform mole should be considered.

Testing

Patients with significant vomiting, signs of dehydration, or both usually require testing. If hyperemesis gravidarum is suspected, urine ketones are measured; if symptoms are particularly severe or persistent, serum electrolytes are measured. If fetal heart sounds are not clearly audible or detected by fetal Doppler, pelvic ultrasonography should be done to rule out hydatidiform mole. Other tests are done based on clinically suspected nonobstetric disorders (see Table 3: Symptoms During Pregnancy: Some Causes of Nausea and Vomiting During Early Pregnancy).

Treatment

Pregnancy-induced vomiting may be relieved by drinking or eating frequently (5 or 6 small meals/day), but only bland foods (eg, crackers, soft drinks, BRAT diet [bananas, rice, applesauce, dry toast]) should be eaten. Eating before rising may help. If dehydration (eg, due to hyperemesis gravidarum) is suspected, 1 to 2 L of normal saline or Ringer's lactate is given IV, and any identified electrolyte abnormalities are corrected.

Certain drugs (see Table 5: Symptoms During Pregnancy: Suggested Drugs for Nausea and Vomiting During Early Pregnancy) can be used to relieve nausea and vomiting during the 1st trimester without evidence of adverse effects on the fetus.

Table 5
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Suggested Drugs for Nausea and Vomiting During Early Pregnancy Drug Dose Vitamin B6 (pyridoxine) 25 mg po tid Doxylamine 25 mg po at bedtime Promethazine 12.5–25 mg po, IM, or rectally q 6 h as needed Metoclopramide 5–10 mg q 8 h po or IM Ondansetron 8 mg po or IM q 12 h as needed

Vitamin B₆ is used as monotherapy; other drugs are added if symptoms are not relieved.

Ginger (eg, ginger capsules 250 mg po tid or qid, ginger lollipops), acupuncture, motion sickness bands, and hypnosis may help, as may switching from prenatal vitamins to a children's chewable vitamin with folate.

Key Points

• Vomiting during pregnancy is usually self-limited and responds to dietary modification.
• Hyperemesis gravidarum is less common but is severe, leading to dehydration, ketosis, and weight loss.
• Nonobstetric causes should be considered.

Last full review/revision August 2009 by R. Phillips Heine, MD; Geeta K. Swamy, MD