David replies:

Hi Richard,

Although the circumstances you describe seem pretty benign the bottom line is that if moisture from your penis came in contact with her vulva then there's some greater-than-zero risk of pregnancy.

You want to know my gut feeling about this? If you're worried enough to ask then yeah, you definitely should communicate with her. And if you're worried enough to ask then if it's been less than five days since you had sex (remember "sex" isn't just intercourse!) then she should consider taking an emergency contraceptive.

So. How did I assess your risk? I went to the Scarleteen Easy Pregnancy Risk Assessments page. That has links to several sets of questions and answers about different kinds of sex that do a very good job of helping you decide what to do. Your specific circumstance was a little tricky since you didn't exactly have regular vaginal intercourse but that skin-to-skin contact made it much more than "dry humping." So I cheated a little and read those two plus the questions about manual sex (e.g. handjobs and fingering.) The upshot is that while the risk is low it's definitely not zero so act sooner rather than later.

---

One other thing I really, really want to stress, Richard. You say you "gapped about it," and didn't think about the pregnancy risk till later, and you wondered if you should share your concern. I'd like you to consider that you both did -- you're the one who said she sat on you, right? So it's not just you, you're both responsible. If one of you has anything to worry about then think about worrying about it together.