Why would my ob ask me to get a nonstress test? I'm 36 weeks and having occasional contractions.

Nonstress test. A nonstress test (nst) is a screening test used in pregnancy to monitor the fetal heart rate. The idea is that a healthy fetus will have a temporary increase in the heart rate spontaneously. It is part of making sure the baby is healthy especially if you are having contractions.
Fetal Well Being. The nst is a test for fetal well being. It monitors fetal heart rate. The beat-to-beat variability tells you the following: a) high bbv is good b) low or absent bbv may indicate distress and may need further testing or delivery.
Ask him/her. There are several indications for fetal surveillance (non-stress testing and amniotic fluid index or afi vs. Bpp or full biophysical profile) once or twice weekly after 32 weeks in general. Only your doctor can explain your condition on the basis of your history and examination, however fetal surveillance in general has helped decrease the perinatal fetal loss rate in the us despite comorbidities.