Booking for baby with miles

Q. Is there a charge for infants (under 2 years of age) to fly with me if I book a ticket using my miles?  I have United MileagePlus points, and I cannot find the answer anywhere.  Even the airline’s customer service representatives will not give me a straight answer.

A. Not for a domestic ticket as long as the child sits in your lap. However on international flights, airlines typically charge 10% of the "applicable adult fare" and sometimes add fuel surcharges, so it can be quite costly.