If they were done in our own lab, we get hard copies moments after the test is done, and these go in our chart, plus we write the results on our flowsheets. If they go down to the main lab, it's the RN and MD's responsibility to look the results up in the computer and alert each other that they've seen the labs. If it's a critical result, the RN is called by the lab before it's even in the computer, and we tell the docs.
We usually just call the docs with our lab results, and they just write them down on their papers that they carry around each day/night. They note everything about the babies on those papers (vent settings, IVs, meds, labs, any changes or issues they're having, etc.) and it's what they use to do rounds and give their sign-out. We write all the lab results on our nursing flowsheets, plus official reports are available in the computer at all times, and we also print out daily hard copies to keep in the charts.
We'll report the labs (normal or abnormal) ASAP to the docs, especially during the day. At night, all blood gasses and CBCs are reported ASAP to the docs. If the docs are sleeping, we won't wake them up for routine things like medication peaks and troughs, bilirubin levels, lytes, glucose, etc. - IF there is no change that's going to be made (ex. med that was tested for peak and trough isn't due again until noon the next day, bili level was normal, lytes and glucose were normal, etc.). Usually with labs like that, at night, we'll wait until someone has to call the doc and then we'll all report at the same time, rather than calling every 10 mintues.