you have probably heard that they should be avoided due to the nitrate content, as these can affect blood oxygenation levels causing methemoglobinemia in infants. While this is true, the amounts needed to cause harm are often very high. The water used to prepare infant formulas is often one of the most reported sources of this condition in infants.
Spinach is an excellent source of nutrients and contains good amounts of iron. Occasional intake of this food does not represent a risk for infants who are starting complementary feeding (around 6 months of age) and on the opposite, it can provide a great variety of nutrients.