What is the treatment for a 31-year-old (G2P1) pregnant woman at 14 weeks gestation with unknown gestational diabetes mellitus (GDM) status, experiencing vomiting after every meal and tachycardia?

Treatment of Hyperemesis and Tachycardia at 14 Weeks Gestation

This patient requires immediate antiemetic therapy with first-line agents (vitamin B6 plus doxylamine or ondansetron), intravenous fluid resuscitation for dehydration-induced tachycardia, and urgent evaluation to rule out thyrotoxicosis and other causes of tachycardia before attributing symptoms to hyperemesis alone.

Immediate Management Priorities

Address Dehydration and Tachycardia

• Administer intravenous normal saline or lactated Ringer's solution to correct volume depletion, which is the most common cause of tachycardia in hyperemesis gravidarum. The tachycardia should resolve with adequate hydration.
• Check orthostatic vital signs to assess degree of volume depletion.
• Obtain baseline electrolytes (particularly potassium, magnesium), renal function, and urinalysis for ketones to assess severity of dehydration.

Rule Out Thyrotoxicosis

• Measure TSH and free T4 immediately, as gestational transient thyrotoxicosis occurs in up to 60% of women with severe hyperemesis and can cause both vomiting and tachycardia.
• If TSH is suppressed with elevated free T4, this represents hCG-mediated thyrotoxicosis that typically resolves without treatment as hCG levels decline after first trimester, but may require beta-blockers for symptomatic tachycardia.

Exclude Other Causes of Tachycardia

• Obtain complete blood count to rule out anemia.
• Consider pulmonary embolism if tachycardia persists despite rehydration (though less common at 14 weeks).
• Assess for signs of infection (urinary tract infection, pyelonephritis).

Antiemetic Therapy

First-Line Medications

• Start vitamin B6 (pyridoxine) 25 mg three times daily plus doxylamine 12.5 mg three to four times daily as the preferred initial regimen due to extensive safety data in pregnancy.
• Alternatively, use ondansetron 4-8 mg orally or IV every 8 hours if vitamin B6/doxylamine combination is ineffective or not tolerated.

Second-Line Options if First-Line Fails

• Metoclopramide 10 mg orally or IV every 6-8 hours.
• Promethazine 12.5-25 mg orally, rectally, or IV every 4-6 hours.
• Prochlorperazine 5-10 mg orally or IV every 6-8 hours.

Severe Refractory Cases

• Methylprednisolone 16 mg orally or IV every 8 hours for 3 days, then taper (use only after 10 weeks gestation and after other options exhausted).
• Consider hospitalization for continuous IV fluids and antiemetics if unable to tolerate oral intake.

Nutritional Support

• Thiamine supplementation 100 mg daily is critical before starting IV dextrose to prevent Wernicke encephalopathy in women with prolonged vomiting.
• Start with small, frequent meals (every 1-2 hours) of bland, dry, high-protein foods once vomiting controlled.
• Avoid iron supplementation temporarily if it worsens nausea.

Gestational Diabetes Screening Considerations

Current Status at 14 Weeks

• GDM screening is NOT indicated at 14 weeks for routine-risk patients, as standard screening occurs at 24-28 weeks gestation 1.
• However, if this patient has risk factors (obesity, prior GDM, family history of diabetes, high-risk ethnicity), she should be tested NOW for undiagnosed pre-existing diabetes using fasting plasma glucose 1, 2.
• If early screening is negative, repeat standard GDM screening at 24-28 weeks 1.

Risk Factors Requiring Early Testing

• Age >25 years (this patient is 31) 1.
• Obesity (BMI >30 kg/m²) 1.
• First-degree relative with diabetes 1.
• High-risk ethnicity: Hispanic, Native American, Asian American, African American, or Pacific Islander 1.
• History of GDM in prior pregnancy 1.
• History of macrosomic infant 1.

If Early Testing Shows Diabetes

• Insulin is the preferred medication for treating hyperglycemia in pregnancy, as it does not cross the placenta 1, 2.
• Target fasting glucose <95 mg/dL, 1-hour postprandial <140 mg/dL, or 2-hour postprandial <120 mg/dL 1, 2.
• Metformin and glyburide should NOT be used as first-line agents because they cross the placenta, and metformin exposure is associated with higher offspring BMI and increased obesity risk at ages 4-10 years 1, 2, 3, 4.

Critical Pitfalls to Avoid

• Do not assume tachycardia is solely from hyperemesis without checking thyroid function and ensuring adequate hydration.
• Do not delay antiemetic therapy waiting for "natural resolution"—untreated hyperemesis can lead to Wernicke encephalopathy, electrolyte abnormalities, and poor pregnancy outcomes.
• Do not start IV dextrose before giving thiamine in women with prolonged vomiting.
• Do not screen for GDM at 14 weeks unless risk factors present for pre-existing diabetes 1.
• Do not use metformin or glyburide as first-line therapy if diabetes is diagnosed, as both cross the placenta with concerning long-term offspring outcomes 1, 2, 3, 4.

Follow-Up Plan

• Reassess hydration status and vital signs after 1-2 liters IV fluid.
• If tachycardia persists despite adequate hydration and normal thyroid function, consider cardiology consultation.
• Once vomiting controlled and patient tolerating oral intake, transition to oral antiemetics and discharge with close outpatient follow-up.
• Repeat standard GDM screening at 24-28 weeks even if early testing was normal 1.