DEAR ANDREA: I had to respond to your "pregnant from anal sex" column, because I've had the same question. The fact is, after anal sex the semen does not stay tidily inside. There's a trickle-down factor. And one thing I can say about sex education in the United States is that, full of scare stories as it is, one sure does hear about how there's a slim but not off-the-radar chance of sperm ejaculated outside of the vagina-but darn close making its way inside. Especially if things are all nice and juicy down there.

So, here's your scenario. Couple has unprotected anal sex. Woman is very turned on; vagina is highly lubricated due to said arousal. Man ejaculates; they sit up and have a cigarette or whatever the kids are doing these days. Semen follows gravity's pull, drips out into the genital area, is conducted further via the general gooshiness factor. OK, obviously tons of folks aren't getting pregnant this way or we'd be hearing about it, but that's not the question. The question is, is it possible? The only way I can figure it wouldn't be is maybe the internal temperature in the anus is high enough to do in the sperm? Or maybe they're (eeew!) contaminated in some way by the environment? Or, the seminal fluid just doesn't drip out in enough volume to make this a liability?

I have to say, this is one I've pondered over the years myself, as there's little in the literature targeted at nice girls who happen to enjoy anal sex (it's usually, "if a man insists on doing this awful thing, here's how to put up with it"). And sure, one probably shouldn't be having unprotected anal sex, but again, that wasn't the issue at hand, as it were.

Love, Friend of a Friend of a Friend

Dear Friend: I'm running your letter for a number of reasons, none of which has a thing to do with the issue's earth-shaking importance. Rather, yours represents a flood of similar letters (OK, four) and is the best-written of the lot. Clearly, this subject struck a chord with people, though I am at a loss to understand why. Are innocent girls really getting knocked up in droves from unprotected anal sex? Has my membership in the secret sex-expert's cabal expired, am I just behind on my reading, or what?

The truth is, I must make the best use of my limited space, which means that many of the outliers on life's little bell curve never make the cut. Sure, it's possible that a husband's pocketful of motel receipts and condom wrappers indicates something other than adultery, or that somewhere there's a club filled with eager women ready to do it (for free) with the next guy who asks, but it ain't bloody likely. It is likewise possible for the occasional valiant sperm cell to slide free of a woman's rectum and thrash its way salmonlike upstream, but it's barely likely enough to merit a mention. I would have said all this if I'd had the space to spare.

In your entertaining example, the couple (fluid-bonded, we hope) completes the act and then sits up. At this point, wouldn't all of your vividly imagined juices flow downward, away from the vagina, carrying with them any tributaries encountered along the way? If there were any tributaries, that is. The lining of the rectum is too absorbent to allow that much to escape.

This all might need more research, but it currently appears that the sperm that end up doing the actual insemination probably come from the "seminal pool," the deposit of semen that collects just under the cervix. The fresh semen gels so it won't trickle down just yet and (so goes the theory) is literally sucked up into the cervix. The contractions of the woman's orgasm, it is posited, could help with the hoovering action. Afterward the cervix returns to its usual elevated position, and the unused semen reliquefies and runs down your leg. None of this bodes well for our little lost sperms finding their way upstream.

Of course, it's possible for semen that lands far afield of the seminal pool to manage to fertilize someone, usually an incautious but hyperfertile teenager. Anything that can happen does happen. We know this, but we do not bet the farm on it.

Love, Andrea