Originally Posted by slidergirl

From delta.com:
"International Taxes & Fees—For infants under the age of two and held in the adult's lap, the cost is usually about 10% of the adult fare plus any international taxes and surcharges, which can be significant."

As others have said, your child's ticket may end up pretty pricey if you are using your miles in BE. Hard to swallow, especially if you are going to have your child in your lap for that entire flight. Good luck (honestly).