Screening for New-Onset Nausea in Third Trimester
New-onset nausea in the third trimester is atypical and should trigger immediate screening for serious pathology including preeclampsia, acute fatty liver of pregnancy (AFLP), gastrointestinal emergencies, and thromboembolic disease—this is NOT typical pregnancy-related nausea which resolves by 20 weeks in 90% of women 1.
Critical Red Flag Symptoms to Screen
Hepatic/Metabolic Emergencies
Screen immediately for acute fatty liver of pregnancy by assessing:
- Abdominal pain (especially right upper quadrant)
- Jaundice or dark urine
- Altered mental status or confusion
- Hypoglycemia symptoms (shakiness, confusion)
- Easy bruising or bleeding (coagulopathy)
AFLP typically presents in the third trimester with nausea, vomiting, and abdominal pain, and carries high maternal-fetal mortality 2. The Swansea criteria should guide diagnosis, looking for leukocytosis, hyperbilirubinemia, elevated liver enzymes, hypoglycemia, hyperuricemia, acute kidney injury, and coagulopathy 2.
Preeclampsia/HELLP Syndrome
- Severe headache
- Visual disturbances (blurred vision, scotomata)
- Right upper quadrant or epigastric pain
- Sudden weight gain or edema
- Blood pressure elevation
Gastrointestinal Catastrophes
Screen for surgical emergencies that can present with vomiting in late pregnancy:
- Severe, persistent abdominal pain (consider bowel obstruction, volvulus, appendicitis)
- Abdominal distension
- Inability to pass stool or flatus
- Fever
Third-trimester vomiting has been associated with maternal small bowel volvulus, ileocecal abscess from Crohn's disease, and other surgical emergencies 3. Persistent vomiting after the first trimester should be considered an alarm symptom requiring investigation 3.
Respiratory/Thromboembolic Disease
- Dyspnea or shortness of breath
- Chest pain
- Hemoptysis
- Tachycardia or palpitations
- Leg pain or swelling (DVT)
Pregnant patients with nausea/vomiting are at increased risk for pulmonary embolism due to dehydration, immobility, and pregnancy's prothrombotic state 4. PE can present suddenly with hemoptysis, chest pain, and respiratory distress 4.
Urinary/Renal Symptoms
- Flank pain
- Dysuria or urinary frequency changes
- Fever or chills
Acute pyelonephritis can present with vomiting in the third trimester 3.
Severe Respiratory Distress
- Intractable cough
- Severe dyspnea
- Chest pain
Consider diaphragmatic hernia, which can be exacerbated by vomiting and present with mediastinal shift and cardiorespiratory failure 5. While rare, this should be excluded if symptoms are intractable, especially with dyspnea 5.
Assessment Approach
Do NOT use typical first-trimester nausea assessment tools like PUQE for third-trimester onset nausea, as these are validated only for early pregnancy nausea 1. Instead:
Obtain detailed history focusing on:
- Timing and pattern of symptoms
- Associated symptoms listed above
- Ability to maintain oral intake
- Signs of dehydration
Perform targeted physical examination for:
- Blood pressure
- Signs of dehydration
- Abdominal tenderness or guarding
- Respiratory distress
- Lower extremity edema or tenderness
Order appropriate investigations:
- Complete blood count (leukocytosis, hematocrit)
- Comprehensive metabolic panel (liver enzymes, bilirubin, glucose, urea, creatinine)
- Uric acid
- Coagulation studies
- Urinalysis and urine culture
- Consider imaging based on clinical suspicion
Key Clinical Pitfall
The most critical error is assuming third-trimester nausea is "normal pregnancy-related nausea." Normal nausea and vomiting of pregnancy resolves by 20 weeks in 90% of women 1. New-onset or persistent symptoms beyond this point warrant investigation for secondary causes 6, 3.