Infidelity is more likely to occur during certain points in a marriage than others. External pressures, stress, illness, even changes in society can affect a couples' risk for infidelity.
Risk of infidelity increases:
After the 1st year of marriage
Once the "honeymoon" period is technically over, marital couples settle
into everyday life with each other. Routines are established, partners become
comfortable, and the "lovely-dovey" newlywed behavior is gone. Many couples
do not continue to date and/or maintain pre-marital interactions that strengthen
their relationship.
Once the first child is born
Children bring joy and excitement to a marriage. For first-time parents, the
worry and stress associated with parenting takes their focus off of the marital
relationship. The child becomes the most important thing in the family. Not able to
effectively deal with parental stress, couples' can increase their risk for divorce.
Between year 5 and year 7
Called the "seven year itch", this period occurs when daily routines and focus on children
can decrease the friendship, respect and love which once existed in the relationship.
Partners may look outside of the relationship for the excitement they felt during dating or
the first year of marriage.
Middle age
There is some debate as to the validity of the "midlife crisis", in which individuals attempt
to recapture their youth. What is true is that during this period, many evaluate their lives
and whether or not they reached long-term goals. This process of change can cause stress
and conflict within the relationship increasing risk for divorce. Also, as people are living
longer, more and more choose to live their final 30-40 years with someone new.
Source: Facts About Infidelity