If you choose a plant-based diet, supplement properly
(snip) vegan-friendly DHA supplements extracted from algae are available. (snip) These supplements are more expensive and contain lower concentrations of DHA than fish or krill oil supplements (meaning higher doses are recommended), but may be important for maintaining healthy DHA levels, particularly in mothers and babies during pregnancy and while breastfeeding.
Directly consuming seaweed and other forms of edible algae instead of taking algae oil extracts is unreliable, because it's unclear whether the DHA within these fibrous foods can be released and absorbed by the human body; in other words, the DHA in edible algae may not be bioavailable. All baby formula in the U.S. is supplemented with DHA already, in an effort to mirror human mother's milk, which naturally contains DHA. If weaning your child before age 2, be sure to include DHA in your child’s diet as food or supplements.
I wonder if there is vegan baby formula, given animal source DHA is cheaper and companies cost optimise