ChristensenCT,
While I do believe that this is another form of peer pressure or stereotype, I will tell you that my sister's husband is in the Army and they have 3 kids that are were born 2003, 2004 and 2005. As my dad so aptly put it "They do know what causes that now".
As long as you use care to be responsible during any sexual relationships you may have upon the end of your tour, you should not fall into this stereotype. Just take your time and protect yourself and your partner.
<3
Nikki