Did they control for causes of heavier coffee consumption?
I drink more coffee when I have to work longer hours and/or with frustrating co-workers and clients. I imagine these sorts of stresses would not contribute to a healthy pregnancy, no matter what drugs I was or was not consuming.
That said, I routinely give up alcohol for 6-7 weeks at a time (Lent), but could not fathom going off coffee that long, much less 9 months. I'd suck it up for the sake of my theoretical child, but I don't think it'd be easy.
@ Alacrity: A good childhood friend who was something of a party girl swore her pregnancy caused an aversion to even the smell of alcohol and pot. I had been worried that she would be able to refrain from drinking or smoking for 9 months, but she did, and still only has two drinks a week at most while breastfeeding, and doesn't go near pot anymore. It also stopped her smoking tobacco. She's become even more of a hippie, though...
(Tux, because it isn't Linux users who cause me professional grief, and in honor of my pinko commie hippie friend)