Fair city’s surrogacy story

It is a load of convoluted nonsense but here goes:

Junior (Wayne and Orla's son) has some condition whereby he needs stem cells. There are no family members compatible. Wayne is not the biological father but Tommy is. Only another child by Tommy and Orla would be compatible. Wayne and Orla get Tommy to give a sperm sample so that Orla's fertilised egg can be implanted in a surrogate. They tell Tommy that the surrogate will be in the USA and the child will stay there. Instead they get Sash to head to Prague where she is implanted. Many months later Sash returns and no one lets on to Tommy that the child is his. Dolores finds out the truth and tells Pete who in turn tells Tommy. Tommy is not best pleased.

Why didn’t Tommy just give Orla a good old rattle.