The divorce rate for all childless couples is 66% (don't have the numbers for those who made a conscious decision not to procreate). The divorce rate for couples with children is around 40%, and it is slightly higher for those with only girls than it is for those with only boys.
Not having children, especially when it is not by choice, is very hard on people which by extension becomes hard on the marriage.
When you are faced with a spouse who either subliminally or openly states that the fact that you don't have children is your fault something inside you begins to shrivel up and die. Especially when you blame yourself as well.