"Sex While Pregnant" joke

For those of you about to become first-time fathers, you should know something that us old pros do: there are three stages of sex with your mate during pregnancy.
During the first trimester, you do it regular style. During the second trimester, you do it doggie style.
During the last trimester, you do it wolf style. "What the heck is wolf style?" you ask. That's when you sit by the hole and howl!