Objective: To evaluate the shortening of the time of nonstress test (NST) by using transabdominal fetal
stimulation with halogen light.
Study design: Experimental research
Material and Method: The authors enrolled 176 pregnant women between 32 and 42 weeks of gestation
indicated for NST at the Division of Maternal Fetal Medicine, Siriraj Hospital, Mahidol University. They were
randomly assigned to receive either NST (control) or halogen light stimulation test (LST). The stimulation
was performed at the beginning of the test and repeated every 10 minutes until reassuring fetal heart rate
(FHR) acceleration was achieved, or up to 3 times. All tracings were interpreted blindly by one investigator
at the end of the tests.
Results: The mean (+ SD) duration from starting the test to the first FHR acceleration was not significantly
different between the control group and the LST group (5.6 + 7.2 and 5.4 + 5.2 minutes, respectively). The
average testing time (+ SD) to achieved reactivity was 10.5 + 8.8 minutes in the controls and 9.6 + 6.7 minutes
in the LST group. This was not statistically different. The incidence of nonreactive tests was not significantly
different between the LST and the controls (15.9% and 11.4%, respectively). Among the LST subjects, term
fetuses and women with BMI < 27 kg/m2 required less time to reach reactivity, 2.4 and 2.3 minutes respectively.
Conclusion: Transabdominal halogen light stimulation did not shorten the duration of NST in the presented
population. However, the presented data suggests that the fetus at term could respond to visual stimulation,
especially when the gestational age is more advanced.

Keywords: Halogen light stimulation test, Fetal well-being, Nonstress test, Fetal heart rate reactivity, Fetal
physiology