Let me be delicate about this, if I can.
As far as I can tell, not only should you be having lots of oral sex with the father of your baby—even up to a year before conceiving—you should also make sure to ingest his seminal fluid. Listen to what I'm telling you: the international medical community is giving you an Rx for oral. Sure, they say frequent intercourse is good, too, but oral is better. So, if you care about having a healthy baby and not potentially unleashing what scientists call a "destructive attack on the foreign tissues" of your fetus, if you want to avoid immunological disorders during pregnancy, and I'm sure you do, get to work. Or to pleasure, depending on how you feel about it. The Etiquette of Oral Sex
Basically, the research says you need to be able to tolerate your baby's foreign, paternal DNA; in other words, you need to get your body accustomed to the stuff, need to cozy up to some daddy double helix for a while so your body doesn't reject it.
I'm no doctor, just a pregnant lady with Google, so maybe I'm horribly confused, but here is what I found excerpted online, from the Journal of Reproductive Immunology:
"While any exposure to a partner's semen during sexual activity appears to decrease a woman's chances for the various immunological disorders that can occur during pregnancy, immunological tolerance could be most quickly established through oral introduction and gastrointestinal absorption of semen."
I could not make this up. Gastrointestinal absorption of semen. I know. For the man in your life, this news should not be hard to swallow. Sorry.
According to a group of Dutch researchers, "exposure to semen provides protection against developing preeclampsia." That's from a paper with the catchy title, "Immune Maladaptation in the Etiology of Preeclampsia: a Review of Corroborative Epidemiologic Studies." Or you could use the subtitle: "Semen is Your Friend."
I just can't figure out why the whole "blue balls" thing has gotten so much traction with men, but they never got ahold of this medical morsel.