CHARACTERIZATION AND PROGNOSTIC-SIGNIFICANCE OF VARIABLE DECELERATIONS IN THE 2ND-STAGE OF LABOR

The characteristics of variable decelerations (VD) in the second stage of labor and the relationship between the number, frequency or severi ty and neonatal outcome have not been studied. We have analyzed the ch aracteristics of VD in the second stage of labor and their prognostic significance in the prediction of Apgar scores. In this descriptive st udy, fetal heart tracings containing VD from 250 singleton, vaginal de liveries between June 1994 and July 1996 were reviewed blinded to outc ome information. Excluded were: (1) deliveries at <36 weeks, (2) unint erpretable tracing, (3) absence of VD in second stage of labor, and (4 ) absence of exam establishing beginning of second stage of labor. VD characteristics evaluated: shape (U, V, W); anterior and posterior ''s houlders''; slow return to baseline (less than or equal to 30-degree c urve); cumulative depth of VD per 10 min, second stage oxytocin dose. Outcome information collected: method of delivery, birth weight and Ap gar scores. Statistical analysis included regression and analysis of v ariance (ANOVA). The mean maternal age was 32 +/- 5 years and gestatio nal age 39 +/- 1.3 week. In the second stage of labor, the mean oxytoc in dose was 3 +/- 5 mu/min, length of the second stage 65 +/- 57 min, total number of VD averaged 21 +/- 17 and uterine contractions 26 +/- 22 per patient. The percentage of VD <100 bpm was 50 +/- 27%, VD <70 b pm 13 +/- 20%, anterior shoulders 76 +/- 30%, posterior shoulders 75 /- 30% and slow return to baseline 12 +/- 17%. The number of VD signif icantly increased with the length of the second stage of labor (r = 0. 85, p <0.001). The total number and percentage of VD <70 bpm were inve rsely correlated with 5-min Apgar score (p = 0.038, 0.015 respectively ). The sum of the depth of VD/length of second stage as well as the pe rcentage of VD with anterior and/or posterior shoulders and slow retur n to baseline were not significantly related to Apgar sco es (p = 0.08 , 0.72, 0.73, 0.99, respectively). Patients with a higher percentage o f decelerations with slow return to baseline had a higher rate of oper ative vaginal deliveries (20 vs. 11%, p = 0.002); but no significant d ifferences in Apgar scores compared with those with spontaneous delive ry (p = 0.9). Second stage VD <70 bpm were significantly associated wi th lower 5-min Apgar scores. Although the presence of VD with a slow r eturn to baseline was significantly associated with operative delivery , there was no difference in 5-min Apgar scores.