:: One could posit that inserting a penis into a vagina stands as least as much of a chance of disrupting the environment as inserting fingers would.  If a woman is using FA for birth control, it'd be almost impossible to determine whether the fingers or the penis were causing a change.  Plenty of women regularly masturbate with fingers inserted vaginally, or allow partners to masturbate them with fingers inserted vaginally.  I think the current mention of possible environmental changes through digital penetration is enough.  I say, don't cite it.