What is the expected impact of untreated hyperthyroidism on the fetus during pregnancy?

Untreated hyperthyroidism in a pregnant individual can lead to several significant impacts on the fetus, most notably through the potential for fetal thyroid stimulation. When hyperthyroidism is present, particularly in the form of conditions such as Graves' disease, there is a risk of the mother producing thyroid-stimulating immunoglobulins that can cross the placental barrier. This can subsequently stimulate the fetal thyroid gland, leading to hyperthyroidism in the fetus itself.

Research indicates that this fetal thyroid stimulation can occur in about 1% of cases when mothers are hyperthyroid, particularly if they have untreated or poorly managed thyroid conditions. This can result in complications such as fetal tachycardia, low birth weight, and potential fetal demise in more severe cases. Hence, the correct understanding of the impact of untreated hyperthyroidism emphasizes the risk of fetal thyroid stimulation as a direct consequence of maternal hyperthyroidism.

In contrast, the other options reflect complications that are either not directly attributable to untreated hyperthyroidism or misrepresent the actual outcomes. For example, increased fetal weight is typically associated with conditions such as gestational diabetes rather than hyperthyroidism. Similarly, while untreated hyperthyroidism may increase the risk of complications, it does not significantly correlate with nutrient