As with so many things in diving, it comes down to risk tolerance. As the study quoted above shows, there is no good evidence that diving -- even "real" diving to depth -- has a powerful deleterious effect on pregnancy. But no one knows where the line should be drawn, and NO ONE is willing to accept ANY increased risk of a problem with a pregnancy. There is a baseline rate of birth defects, so even a pregnancy conducted entirely within what we now consider the "rules" has a chance of ending abnormally. If one had been diving during the pregnancy and the baby was abnormal, one would always wonder and perhaps carry guilt about it. Better to avoid the issue. And I hate saying that, because at heart I'm really a rational person and would like to be able to offer good data to show that what you propose is dangerous -- which it probably isn't.