Lithium is an effective medicine for bipolar disorder, but during pregnancy, it must be used with careful medical supervision. Studies show a small increased risk of heart defects in the baby, particularly a rare condition called Ebstein anomaly (affects the tricuspid valve, which controls blood flow on the right side of the heart), mainly when lithium is taken during the first trimester. Some newborns may also have temporary problems such as feeding difficulty, low muscle tone, or thyroid and kidney issues after birth. Because of these risks, doctors monitor lithium blood levels closely during pregnancy, as they can change with fluid balance and kidney function. In some women, lithium may still be continued if the benefits outweigh the risks, but this decision must be guided by a specialist. Alternative options may include certain antipsychotic medications, such as quetiapine or olanzapine, or lamotrigine for mood stability in selected cases. Medicines like valproate are usually avoided in pregnancy due to the higher risk of birth defects. Careful planning before conception and regular prenatal check-ups, including heart scans of the baby, are very important.