Merck Manual

Please confirm that you are a health care professional


Nausea and Vomiting During Early Pregnancy


Geeta K. Swamy

, MD, Duke University Medical Center;

R. Phillip Heine

, MD, Duke University Medical Center

Last full review/revision Jul 2018| Content last modified Aug 2018
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Topic Resources

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.


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.


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

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.


Some Causes of Nausea and Vomiting During Early Pregnancy


Suggestive Findings

Diagnostic Approach


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

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, magnesium, BUN, creatinine

If the condition persists, possibly liver function tests, pelvic ultrasonography

Larger-than-expected uterine size, absent fetal heart sounds and movement

Sometimes elevated BP, vaginal bleeding, generalized edema, grapelike tissue from the cervix

BP measurement, quantitative hCG, pelvic ultrasonography, biopsy


Acute, not chronic; usually accompanied by diarrhea

Normal (benign) abdomen (soft, nontender, not distended)

Clinical evaluation

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 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 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 Relevant Physical Examination Finding in a Pregnant Patient With Vomiting).


Relevant Physical Examination Findings in a Pregnant Patient With Vomiting




Lethargy, agitation


Dry mucosa, icteric sclera


Stiffness to passive flexion (meningismus)


Distention with tympany

Absent or high-pitched tinkling bowel sounds

Focal tenderness

Peritoneal signs (guarding, rigidity, rebound)


Flank tenderness to percussion

Uterus too large for dates

Absent fetal heart sounds

Grapelike tissue from the cervix


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 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.


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 Some Causes of Nausea and Vomiting During Early Pregnancy).


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 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.


Suggested Drugs for Nausea and Vomiting During Early Pregnancy



Vitamin B6 (pyridoxine)

25 mg po tid


25 mg po at bedtime


12.5–25 mg po, IM, or rectally q 6 h as needed


5–10 mg q 8 h po or IM


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.

Drugs Mentioned In This Article

Drug Name Select Trade
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Also of Interest


View All
How to do External Cephalic Version
How to do External Cephalic Version
3D Models
View All
Contents of the Female Pelvis
3D Model
Contents of the Female Pelvis