Via Science Daily:

A statistical analysis showed the following benefits enjoyed by couples who waited until marriage compared to those who started having sex in the early part of their relationship:

* Relationship stability was rated 22 percent higher
* Relationship satisfaction was rated 20 percent higher
* Sexual quality of the relationship was rated 15 percent better
* Communication was rated 12 percent better

For couples in between -- those that became sexually involved later in the relationship but prior to marriage -- the benefits were about half as strong.

Also notable:

Because religious belief often plays a role for couples who choose to wait, Busby and his co-authors controlled for the influence of religious involvement in their analysis.

"Regardless of religiosity, waiting helps the relationship form better communication processes, and these help improve long-term stability and relationship satisfaction," Busby said.