What is the management for a 15-week pregnant woman with a history of in vitro fertilization (IVF) and hyperthyroidism on propylthiouracil (PTU), presenting with persistent vomiting and hypotension?

Management of Persistent Vomiting with Hypotension in a 15-Week Pregnant Woman

This patient requires immediate hospitalization for intravenous fluid resuscitation, correction of electrolyte abnormalities, thiamine supplementation, and antiemetic therapy, while simultaneously evaluating for preeclampsia and other pregnancy-specific liver diseases. 1

Immediate Stabilization

Fluid Resuscitation and Monitoring

• Admit to hospital immediately for intravenous hydration given the hypotension (systolic BP 80 mmHg) and persistent vomiting 1
• Administer IV fluids to correct dehydration and restore blood pressure 1
• Correct electrolyte abnormalities, which commonly include hyponatremia, hypokalaemia, and metabolic hypochloraemic alkalosis 2
• Administer thiamine (vitamin B1) supplementation urgently to prevent Wernicke's encephalopathy, a serious complication of hyperemesis gravidarum 1, 2

Antiemetic Therapy

• Initiate antiemetic therapy with ondansetron, which has favorable pregnancy safety 1
• Alternative acceptable antiemetics include metoclopramide and promethazine 1
• Oral prednisolone has no proven benefit; intravenous corticosteroids have conflicting data but can be considered for severe refractory disease 1

Diagnostic Evaluation

Rule Out Preeclampsia and Hypertensive Disorders

Critical pitfall: While this patient presents with hypotension, you must still evaluate for preeclampsia, as IVF pregnancy is a risk factor for hypertensive disorders of pregnancy 3. The hypotension may be due to severe dehydration masking underlying hypertension.

• Once stabilized with fluids, reassess blood pressure to determine if hypertension emerges 1, 3
• Check urine protein/creatinine ratio (abnormal if ≥30 mg/mmol or 0.3 mg/mg) 1
• Obtain laboratory tests including: hemoglobin, platelet count, liver function tests (AST, ALT), renal function tests, and uric acid 1

Assess for Hyperemesis Gravidarum

• This clinical presentation is consistent with hyperemesis gravidarum, characterized by prolonged severe vomiting, dehydration, and weight loss ≥5% of prepregnancy body weight 1
• Check for ketonuria and elevated urine specific gravity 2
• Liver enzyme abnormalities occur in ~50% of hyperemesis cases but rarely exceed 1,000 U/L, with ALT typically greater than AST 1
• Important: Biochemical abnormalities typically resolve with hydration and resolution of vomiting; persistent liver chemistry abnormalities despite symptom resolution should prompt investigation for another etiology 1

Thyroid Function Assessment

• Check free T4 and TSH levels, as hyperemesis can cause biochemical thyrotoxicosis with raised free thyroxine and/or suppressed TSH levels 2
• This is distinct from her underlying hyperthyroidism on PTU and represents gestational transient thyrotoxicosis, which rarely requires treatment 4
• Ensure PTU dosing remains appropriate to maintain free T4 in the high-normal range 4, 5

Thyroid Management Considerations

Continue PTU at 15 Weeks Gestation

• At 15 weeks gestation, this patient should remain on PTU rather than switching to methimazole, as the switch is typically planned after week 13-14 but should be deferred during acute illness 3
• PTU is preferred through the first trimester due to methimazole's association with rare fetal abnormalities 3, 6
• Once the acute vomiting episode resolves and the patient is stable, consider switching to methimazole to minimize maternal hepatotoxicity risk in the second and third trimesters 3, 4
• Monitor for PTU side effects including agranulocytosis, hepatitis, vasculitis, and thrombocytopenia 5

Fetal Monitoring

• Confirm fetal well-being with ultrasound assessment 1
• Monitor for fetal thyroid dysfunction, as PTU crosses the placenta and can cause fetal/neonatal hypothyroidism with or without goitre in 9.5% of cases 7
• Fetal thyroid size monitoring by ultrasound is important for appropriate prevention and treatment 7

Common Pitfalls to Avoid

• Do not assume normal blood pressure excludes preeclampsia risk in an IVF pregnancy with severe vomiting—reassess after fluid resuscitation 3
• Do not delay thiamine supplementation, as Wernicke's encephalopathy, central pontine myelinolysis, and death can occur with inadequate treatment 2
• Do not use intravenous hydralazine for blood pressure management if hypertension emerges, as it is associated with more perinatal adverse effects than other drugs 1
• Do not discontinue PTU abruptly during acute illness, as untreated maternal hyperthyroidism increases risks of severe preeclampsia, preterm delivery, heart failure, miscarriage, and low birth weight 4

Expected Course

• Hyperemesis gravidarum is not usually associated with major adverse maternal or fetal outcomes, though low birth weight and premature delivery have been associated 1
• Biochemical abnormalities typically resolve with hydration and resolution of vomiting 1
• Most patients improve spontaneously with intravenous fluids, antiemetics, and supportive care without long-term sequelae 2
• Neonatal thyroid function typically normalizes during the first month of life without treatment in most cases of PTU exposure 7