A new definition of pregnancy?

Few on Twitter will have missed the recent uproar at Arizona’s passing of a new bill pertaining to abortion. On such a divisive subject, it certainly brought out the feisty nature in people.

The key elements of the law change seem to be twofold: bringing forward to 20 weeks the “point of viability” that defines the time after which a woman cannot have an elective abortion; and bringing forward to seven weeks the point until which medication abortion pills can be prescribed.

I find that Twitter’s users, certainly those that I follow, lean further to the left than the average person. And so as you might imagine, reaction from some was fierce.

But rather interestingly, while some have debated the key elements of the change, some have picked up on what on first impressions might appear to be an odd definition of when pregnancy starts, in my view missing the point altogether.

The bill defines pregnancy as starting at the date of the last menstrual cycle. On average, this is two weeks before conception. What? pregnancy starts before the woman has been impregnated? How can this be so?

The trouble with this argument is that this definition is consistent with that used by every doctor in the land: Stateside and in the UK, across the entirety of the developed world, and, I expect, worldwide. Because while a human’s gestation averages 38 weeks, we add two weeks to this when referring to the length of the pregnancy. This effectively measures the journey of the egg, rather than that of the embryo, conception generally happening two weeks after the egg leaves basecamp.

So effectively, a woman could conceivably (ha!) be a virgin for the first two weeks of her naturally-conceived pregnancy, such is the measure we use.

If nothing else, the headline that pregnancy starts before intercourse has brought additional publicity to the bill, claiming that the bill is not only introducing new measures, but also changing the very definition of pregnancy.

While you may have issues with the bill, it’s probably best to focus on the fundamental changes it brings about, rather than the headline-writer’s rather idiotic interpretation.


One Response to “A new definition of pregnancy?”

  1. Christina on April 14th, 2012 18:25

    Thank you. This was brought to my attention this morning and I immediately went to go find out what all the furor was about. The fact that pregnancy has always been thus defined and simply stating the fact is to remove any ambiguity from the law seems to escape everyone’s attention.

    Thank you for your even-handed approach to this new “controversy”.

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