Ricky tells Sammy that he's been married for "over 12 years" but Lucy and Ricky have been married for 13 years and the audience even sees them celebrating their 13th anniversary earlier in the series.
While Lucy, Dorothy and Sam are admiring the baby, Ricky runs into the nursery to tell Lucy that he smells something burning. Lucy immediately yells, "My chickens! My chickens!" and takes off at a run for the kitchen, while Little Ricky -- awakened by her yelling -- starts crying. A devoted and conscientious mother like Lucy would never yell in the presence of her sleeping child.