Dental caries, also known as tooth decay or cavities, are a possible complication of ready-to-use infant formula. This type of formula is a liquid breast milk substitute that does not need to be mixed with water and is sterile and safe for babies. However, it may contain more sugar than powdered or concentrated formula and can cause tooth decay if the baby’s teeth are exposed to it for long periods of time. For example, if the baby falls asleep with a bottle of ready-to-use formula in his or her mouth, the sugar can pool around the teeth and erode the enamel. To prevent dental caries, the baby should not be put to bed with a bottle of formula and should have his or her teeth cleaned regularly with a soft cloth or a baby toothbrush.

Choice A is wrong because poor weight gain is not a complication of ready-to-use infant formula. This type of formula provides adequate nutrition and calories for normal growth and development of infants. Poor weight gain may be caused by other factors, such as illness, feeding difficulties, or inadequate intake.

Choice C is wrong because iron deficiency anemia is not a complication of ready-to-use infant formula. This type of formula is fortified with iron and can prevent or treat iron deficiency anemia in infants who are not breastfed or are partially breastfed .

Iron deficiency anemia may be caused by other factors, such as blood loss, infection, or low iron intake from complementary foods.

Choice D is wrong because constipation is not a complication of ready-to-use infant formula. This type of formula has a similar composition and consistency to powdered or concentrated formula and does not cause constipation in infants.

Constipation may be caused by other factors, such as dehydration, low fiber intake, or medication.