At the beginning of each fetal movement-an nst assesses the fhr during fetal movement. in a healthy fetus, the fhr accelerates with each movement. By pushing the control button when a fetal movement starts, the client marks the strip to allow easy correlation of fetal movement with the fhr. The FHR is assessed during uterine contractions in the oxytocin contraction test, not the nst. Pushing the control button after every three fetal movements or at the end of fetal movement wouldn't allow accurate comparison of fetal movement and FHR changes.