Fetal Diagnosis. Evaluation of fetal thyroid function is somewhat controversial. Although the fetal thyroid volume can be measured sonographically in women taking thionamide drugs or in those with thyroid-stimulating antibodies, most investigators do not currently recommend this routinely (Cohen, 2003; Luton, 2005). Kilpatrick (2003) recommends umbilical cord blood sampling and fetal antibody testing only if the mother has previously undergone radioiodine ablation. Because fetal hyper-or hypothyroidism may cause hydrops, growth restriction, goiter, or tachycardia, fetal blood sampling may be appropriate if these are identified (Brand, 2005). he Endocrine Society clinical practice guidelines recommend umbilical cord blood sampling only when the diagnosis of fetal thyroid disease cannot be reasonably ascertained based on clinical and sonographic data (Garber, 2012). Diagnosis and treatment are considered further in Chapter 16 (p. 318).
Both of these are acute and life-threatening in pregnancy. hyroid storm is a hypermetabolic state and is rare in pregnancy. In contrast, pulmonary hypertension and heart failure from cardiomyopathy caused by the profound myocardial efects of thyroxine are common in pregnant women (Sheield, 2004). As shown in Table 58-2, heart failure developed in 8 percent of 90 women with uncontrolled thyrotoxicosis. In these women, cardiomyopathy is characterized by a high-output state, which may lead to a dilated cardiomyopathy (Fadel, 2000; Klein, 1998). The pregnant woman with thyrotoxicosis has minimal cardiac reserve, and decompensation is usually precipitated by preeclampsia, anemia, sepsis, or a combination of these. Fortunately, thyroxine-induced cardiomyopathy and pulmonary hypertension are frequently reversible (Sheield, 2004; Siu, 2007; Vydt, 2006).
Management. Treatment is similar for thyroid storm and heart failure and should be carried out in an intensive care area that may include special-care units within labor and delivery (American College of Obstetricians and Gynecologists, 2017). Shown in Figure 58-4 is our stepwise approach to medical management of thyroid storm or thyrotoxic heart failure. An hour or two ater initial thionamide administration, iodide is given to inhibit thyroidal release ofT3 and T4. It can be given intravenously as sodium iodide or orally as either saturated solution of potassium iodide (SSKI) or Lugol solution. With a history of iodine-induced anaphylaxis, lithium carbonate, 300 mg every 6 hours, is given instead. Most authorities recommend dexamethasone, 2 mg intravenously every 6 hours for four doses, to further block peripheral conversion ofT4 to T3. If a 3-blocker drug is given to control tachycardia, its efect on heart failure must be considered. Propranolol, labetalol, and esmolol have all been used successfully. Coexisting severe preeclampsia, infection, or anemia should be aggressively managed before delivery is considered.