What is a significant complication of maternal hyperthyroidism during pregnancy?

Maternal hyperthyroidism during pregnancy can lead to a number of complications, and one of the most significant is maternal heart failure. Hyperthyroidism increases metabolic demands and can lead to an elevated heart rate and cardiac output. In a pregnant woman, these factors can strain the heart, particularly if there is pre-existing cardiac disease or if the hyperthyroidism is poorly controlled. The increased volume of blood and physiological changes in pregnancy, combined with the effects of hyperthyroid state, can precipitate or exacerbate heart failure.

In the case of the other options, increased fetal growth is more commonly associated with gestational diabetes, and hyperthyroidism may lead to intrauterine growth restriction rather than excessive growth. A decreased risk of preeclampsia is not typically noted in cases of hyperthyroidism; in fact, the presence of hyperthyroidism can complicate hypertensive disorders. Lastly, low incidence of gestational diabetes does not correlate with maternal hyperthyroidism, as gestational diabetes can occur independently of thyroid status. In summary, maternal heart failure stands out as a significant potential complication specifically related to the hemodynamic changes caused by hyperthyroidism during pregnancy.