Like any other muscle, it gets bigger/thicker the more you use it.
During conception, the state of you physical health may be passed on to your children or grandchildren.
If you're sick with a cold or more serious illness during conception, it will affect your child.
That's why you should try to be as healthy as possible when trying to conceive.
But I'm not sure if, for example, body builders would have babies with a six pack or developed muscles, which is what the article is sort of implying.