I have had the PregTest for about 6 years now and have had good results with it....mostly once the mares are over 3 months pregnant--you scan in a different area after the foal has dropped (2 inches in front of the udder on the belly). I have had varying results scanning from 14 days to 3 months (on the flank)...I usually will follow-up with a blood test to confirm my results. The drawback to this machine is that you have to actually look (very quickly) at the screen to see the lights--there is no printer function available to record your results. I made my own "recording" sheets that duplicate the screen so I could write my results down after each scan--actually coloring in the dots I saw. I don't feel 100% confident relying soley on this machine, so that's why I follow-up with blood tests. It is also very messy...you have to slather vegetable oil on the scanning area liberally so the probe will engage the flesh accurately...that's the part I hate! Hope this helps.