Barbara,  Thanks for this information.  I can use it to back up some of my own "theories."    But I hope that every one notes the statement regarding use of excessive Mag in severe pre-eclampsia.  What are the guidelines on "excessive" and "severe."  

The main problem that I see arising from this article is people will say, 
"Oh, mom had Mag," and not look for other causes, until well after the Mag should have dissipated from the system in both mom and baby.
Certainly, Mag (and other drugs) may yield transient problems, but I think we need to be looking for and working to ameliorate the other causes as well, so if the baby doesn't recover/discover tone and organization very quickly after cessation of the Mag, we can already be part of the way to the next/correct solution.   

My understanding is that Mag has a very short half-life, and if mom is voiding at least as much as she is taking in between IV and drinking, she is not going to get a very high blood level anyway.  We do not generally do serum Mag levels on our pre-eclamptic moms,  partially for this reason (at least this was the excuse given years ago).   In general our indications for drawing Mag levels are:  1) loss of reflexes if mom is on Mag for its effect on premature labor, 2) continuation of contractions despite what should be a therapeutic dose.   Finally, we draw Mag levels when Input is dramatically higher then Output, since there is then a danger of  a build up beyond therapeutic levels. 

I've seen many moms very sleepy on their Mag, with vigorous babies at the breast.  When the babies were sleepy or disorganized there were also too many  other variables (long labor or pushing, fetal distress, nucchal cords, meconium, epidurals, etc.) to be able to say it came only from the Mag.

Sincerely,  Chanita, San Francisco