A medical study found that women who gave their men oral sex and swallowed had a lower risk of preeclampsia, the dangerously high blood pressure that sometimes accompanies pregnancy. [https://www.ncbi.nlm.nih.gov/pubmed/10706945 ]
In ancient Rome, Os impurum, "filthy mouth" or "impure mouth", was a term of abuse especially for those who provided oral sex. [Wikipedia "Sexuality in ancient Rome"]
