A) Correct answer. Gestational diabetes is associated with an increased risk of congenital heart diseases in the baby. Poorly controlled diabetes during pregnancy can affect fetal development and increase the likelihood of birth defects, including heart defects.

B) This option is incorrect. While preeclampsia is a serious pregnancy complication, it is not specifically linked to an increased risk of congenital heart diseases.

C) This option is incorrect. Hyperthyroidism, an overactive thyroid gland during pregnancy, may pose risks to both the mother and baby, but it is not directly associated with congenital heart diseases.

D) This option is incorrect. Iron deficiency anemia can affect maternal and fetal health, but it is not considered a risk factor for congenital heart diseases.