pets and pregnancy

My wife is pregnant and we are having a disagreement we felt could be resolved here. You see, my wife says that our dog Newton(Dachshound) can "sense that she is pregnant. Does anyone know if pets can detect pregnancy in humans? Thanks.

[double post. See http://boards.straightdope.com/sdmb/showthread.php?threadid=90472 ]

[Edited by bibliophage on 10-02-2001 at 02:47 AM]