Pregnancy Outcome with Overt Hypothyroidism. Observational studies, although limited, indicate that excessive adverse perinatal outcomes are associated with overt thyroxine
TABLE 58-4. Pregnancy Complications in 440 Women with Hypothyroidism a,bBirthweight <2000 gr apreterm or term deliveries were the only outcomes reported by Abalovich, 2002.
SU,r2011.
COne infant died from syphilis.
Data from Abalovich, 2002; Davis, 1988; leung, 1993;
Mannistb, 2009; Su, 2011.
deficiency (Table 58-4). Preterm birth rates, for example, are higher (Sheehan, 2015). With appropriate replacement therapy, however, rates of adverse efects are not increased in most reports (Bryant, 2015; Matalon, 2006; Tan, 2006). In one dissenting study, however, risks for some pregnancy complications were greater even in women taking replacement therapy (Wikner, 2008). Most experts agree that adequate hormone replacement during pregnancy minimizes the risk of adverse outcomes and most complications.
Fetal and Neonatal Efects. Undoubtedly, maternal and fetal thyroid abnormalities are related. In both, thyroid unction is dependent on adequate iodide intake, and its deiciency early in pregnancy can cause both maternal and fetal hypothyroidism. And, as discussed, maternal TSH-receptor-blocking antibodies can cross the placenta and cause fetal thyroid dysunction. Rovelli and colleagues (2010) evaluated 129 neonates born to women with autoimmune thyroiditis. They found that 28 percent had an elevated TSH level on the third or fourth day of life, and 47 percent of these had TPO antibodies on day 15. Still, autoantibodies were undetectable at 6 months of age. It seems paradoxical that despite these transient laboratory findings in the neonate, TPO and anti thyroglobulin antibodies have little or no efect on etalthyroid function (Fisher, 1997). Indeed, prevalence of fetal hypothyroidism in women with Hashimoto thyroiditis is estimated to be only 1 in 180,000 newborns (Brown, 1996).
Although common in women, the incidence of subclinical hypothyroidism varies depending on age, race, dietary iodine intake, and serum TSH thresholds used to establish the diagnosis Qameson, 2015). In two large studies totaling more than 25,000 pregnant women screened in the first half of pregnancy, subclinical hypothyroidism was identified in 2.3 percent (Casey, 2005; Cleary-Goldman, 2008). he rate of progression to overt thyroid failure is afected by TSH level, age, other disorders such as diabetes, and presence and concentration of antithyroid antibodies.
nant women with subclinical hypothyroidism for 5 years and reported that in a third, TSH values became normal. In the other two thirds, those women whose TSH levels were 10 to 15 mUlL developed overt disease at a rate of 19 per 100 patient years. Those women whose TSH levels were < 10rm U IL devel oped overt hypothyroidism at a rate of 2 per 100 patient years.
pregnant individuals, the U.S. Preventative Services Task Force (Helfand, 2004; Karmisholt, 2008).