If your 9-month-old baby has a balanced diet, he/she does not need to take extra DHA supplements. If he/she is a picky eater or partial eater, he/she can take extra DHA supplements as prescribed by the doctor. DHA is docosahexaenoic acid, an unsaturated fatty acid necessary for human growth and development, with various effects, such as assisting brain cell development, anti-aging, lowering blood lipids and improving blood circulation. There are many sources of DHA, among which breast milk or formula milk is the most natural supplement for 9-month-old babies, meanwhile, egg yolk, fish and dried fruits are also rich in DHA. For 9-month-old babies, they should have enough milk and a balanced diet, avoiding partiality or picky eating. DHA supplementation should be taken in accordance with medical advice.