Hello,
I can't give you any long term data, but my 4 month old was also worked up prenatally because of one of these foci. My husband and I are both physician's and were very concerned, as any parent, when told our baby had a heart abnormality. From what we have gathered, it seems like these foci are probably just one of those things that is turning up more often now that we have so much technology to use to spy on our fetuses. The one study that got folks looking for these was a Japanese study, in which they occurred in less than 5% of the population. The prevalence in the melting pot of our countries ethnic smorgasborg is unknown, but it could be about the same. As of last fall, I haven't checked since, there have been no published studies on the long term effects of these calcifications. They are thought to be harmless, and perhaps have always been there; in the past we simply didn't have the technology to observe them. The prenatal/pediatric cardiology specialist we saw told us basically not to worry about the focus. Since our baby was breech, I continued to have a number of ultrasounds up until a week prior to delivery, and the focus actually was almost gone by the time I delivered. I know this isn't the concrete answer you want to hear, but I hope it helps.