Insisting on a test a patient insists she doesn't need

This discussion is from last week's New York Times Well blog but I still think it is worth bringing up. The heated discussion was about physician's who consider women of child-bearing age to be "pre-pregnant," and as such insist on pregnancy tests before certain procedures, even when a woman insists there is no way she could be pregnant.

Of course, it is pertinent for a physician to know if a female patient is pregnant, as certain medications and x-rays are dangerous to an unborn child. And women do not always know when they are pregnant and some may lie about their sexual history and likelihood of being pregnant. But the frustration expressed by many women in the blog discussion shows that some physicians are not approaching this delicate discussion in the most constructive way.

You can find the discussion here:http://well.blogs.nytimes.com/2008/08/28/do-doctors-view-women-as-pre-pregnant/

So how could physicians and patients both approach this conversation in a more positive way?