OK, I've tried for 2 days to find my citation for this, but I'll try to explain it as accurately as I can remember. In our Healthy Pregnancy classes, we were instructed to teach our couples about the dangers of blowing into the vagina DURING PREGNANCY. This is because there is a risk of air being blown between the membranes surrounding the fetus and the uterus, where numerous blood vessels are exposed and dilated to nourish the placenta & baby. There apparently have been documented cases of an air bubble finding its way into the woman's bloodstream this way, where it acts just like a blood clot to prevent blood from getting to the brain/lung/heart, causing tissue damage and even death from stroke. This risk is only during pregnancy and the immediate postpartum period, before the uterus has had a chance to involute. Hope this clears up the question. If anyone would like me to keep on looking for the journal article that describes this, please e-mail me, & I'll check with our other educators, whose files are hopefully more organized than mine! Carol