Fetal surveillance. Should it begin at 40 weeks' gestation in a low-risk population?

We evaluated the possible benefits of antepartum surveillance during the 41st week of pregnancy in a low-risk population. Three hundred low-risk patients (study group) underwent a nonstress test (NST) at the beginning of the 41st week of pregnancy. Outcomes in study group patients who delivered during the 41st week were compared to those in 100 similar control patients who were not tested. One antepartum fetal demise occurred in each group: study group rate, 1/300 (0.3%); control group rate, 1/100 (1%), P > .05. During the 41st week, 158 of 300 (53%) study patients and 59 (59%) control patients delivered. Four of 158 (2.5%) study patients had labor induced for the indication of an abnormal antepartum test during the 41st week. Cesarean delivery for distress during the 41st week was performed on 1/157 (0.6%) study and 1/58 (1.7%) control patients (P > .05). No statistically significant improvement in outcome occurred in the study group even though 4 of 300 study group patients required induction of labor for abnormal antepartum testing during the 41st week of gestation. The current practice of not evaluating low-risk pregnancy with an NST until after the completion of 41 weeks is supported by the results of this study.