The nonstress test

Abstract

The NST has been used extensively in the management of high-risk pregnancies and has been a useful preliminary screening test. However, lack of standardization and multiple testing protocols have made comparisons of reports difficult. The high false-positive rate for protocols not extended for long periods have required back-up testing with other biophysical means whenever there is nonreactivity. Continued research is required to define "normal" reactivity. Meanwhile, ongoing investigations in the area of fetal stimulation may be helpful in arousing the non-reactive sleeping fetus. The benefit of the NST is in its simplicity. Busy practitioners can use it in the office, and large testing centers can screen greater numbers of patients in an effective manner. Given a reactive test, a high expectation of normal outcome is warranted. The false-negative rate, however, for diabetes, postdates, and IUGR, warrant twice-weekly testing. Attention to other baseline characteristics, such as bradycardia and minivariables, coupled with sequential NST evaluation should improve NPV by potentially diagnosing compromise earlier.