Figure 2. Comparison of survival experience suggests that children who were vaginally delivered (N = 127) experienced significantly delayed acquisition of S. mutans compared with the children who were delivered by Caesarean section (N = 29) (p = 0.039). The x-axis is the infant’s age; the y-axis is the probability that children were S. mutans-free (survival) at a given age. Since all children were initially S. mutans-free at birth (100% survival), the y value on the graph starts at 1. On average, children delivered by Caesarean section acquired S. mutans 11.7 mos earlier than did vaginally delivered infants (Wilcoxon statistic; p = 0.039).