If mother received lithium treatment for bipolar disorder during pregnancy, the fetus is likely to show:
**Core Concept**
Lithium is a mood stabilizer used to treat bipolar disorder, but its use during pregnancy poses risks to the fetus. The primary concern is the potential for lithium to cause cardiac malformations, particularly Ebstein's anomaly, a congenital heart defect characterized by an abnormal tricuspid valve and right ventricular hypoplasia.
**Why the Correct Answer is Right**
Lithium crosses the placenta and can affect fetal development, particularly during the first trimester when organogenesis occurs. The exact mechanism of lithium-induced cardiac malformations is not fully understood, but it is thought to involve disruptions in fetal cardiac development, possibly due to alterations in gene expression or signaling pathways. The risk of Ebstein's anomaly in offspring of mothers treated with lithium during pregnancy is estimated to be around 1 in 1,000.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because there is no established association between lithium treatment during pregnancy and an increased risk of fetal neurodevelopmental disorders, such as autism spectrum disorder.
**Option B:** This option is incorrect because lithium treatment during pregnancy is not associated with an increased risk of fetal gastrointestinal malformations, such as intestinal atresias.
**Option C:** This option is incorrect because while lithium can affect fetal thyroid function, there is no established association between lithium treatment during pregnancy and an increased risk of congenital hypothyroidism.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the risk of Ebstein's anomaly in offspring of mothers treated with lithium during pregnancy is dose-dependent, with higher doses increasing the risk.
**Correct Answer:** C. Ebstein's anomaly