Can delayed periods lead to increase in the size of the belly?

At times, because you MAY be pregnant.

Of course, it could also be mental. Some women, when they think that they are pregnant, the body will automatically go into "pregnancy mode," even if they're not, just to prep the body for birth. Even when a woman's not pregnant, she can start to feel sore breasts and their breasts may appear larger, just because she THINKS she's pregnant.

Also, it could also be hormonal changes that is the cause of the delayed period and physical body changes.