## 3 Results
### Multivariate Prediction Models
#### 3.2.1 Logistic Regression  
The construction of the logistic regression model involved a stepwise selection process, employing a backward/forward method. This iterative process involved removing variables based on an improvement in the Akaike index, while also considering the inclusion of variables that were removed from the model if their inclusion improved the index at any step. Table 3 displays the variables that were found to be statistically significant in the multivariate analysis. To illustrate the weight of the variables in the prediction model, we provide a nomogram in Figure 5. The nomogram shows the weight of variables in the model. For each individual, a score is assigned to each variable on the upper axis. By summing up these scores, a total score is obtained, which provides us with the probability of acidosis on the lower axis. Considering the variability of points assigned on the nomogram, the variables that show the most difference are the duration, the drop, and the drop difference. In these variables, we observe more variation among individuals, but both the drop and the drop difference do not yield very high scores compared to the drop. On the other hand, the duration difference, slope, and deceleration area exhibit reduced variability, but due to their \begin{table}
\begin{tabular}{l l l l l l l} \hline  & **Total n = 502** & **Non Acidotic n = 278** & **Acidotic n = 224** & \(p\)**-Value** & **Odds Ratio** & **AUC** \\ \hline \multicolumn{6}{l}{_30 min window_} \\ \hline Deceleration range & 14.16 (7.71, 22.54) & 9.71 (5.37, 15.42) & 20.93 (13.75, 28.65) & \(<\)0.001 & 1.141 (1.112, 1.171) & 0.807 \\ Repperfusion time & 19.35 (15.37, 23.20) & 21.69 (18.10, 25.12) & 17.04 (13.86, 19.10) & \(<\)0.001 & 0.822 (0.787, 0.859) & 0.750 \\ \hline \multicolumn{6}{l}{_Final acceleration window_} \\ \hline Amplitude & 72.99 (54.94, 87.04) & 60.06 (49.96, 74.92) & 84.87 (74.18, 95.11) & \(<\)0.001 & 1.063 (1.050, 1.076) & 0.796 \\ Duration & 71.25 (59.88, 90.69) & 61.8 (55.68, 89.92) & 80.9 (64.32, 100.14) & \(<\)0.001 & 1.023 (1.015, 1.030) & 0.670 \\ Drop & 32.63 (23.26, 46.51) & 40.9 (30.79, 53.47) & 23.96 (19.18, 32.32) & \(<\)0.001 & 0.933 (0.918, 0.947) & 0.792 \\ Slope & 2.08 (13.1, 34.7) & 1.57 (10.12, 2.05) & 3.51 (24.49, 4.69) & \(<\)0.001 & 3.331 (2.681, 4.138) & 0.853 \\ Area & 2.51 (1.89, 37.1) & 2.15 (1.6, 2.72) & 3.55 (2.45, 4.69) & \(<\)0.001 & 2.470 (2.048, 2.979) & 0.781 \\ FHR (ppm) & 155 (145, 165) & 150 (140, 160) & 160 (150, 170) & \(<\)0.001 & 1.043 (1.029, 10.57) & 0.664 \\ Overshoot & 67 (13.35\%) & 24 (8.63\%) & 43 (19.19\%) & 0.001 & 2.514 (1.473, 4.291) & 0.552 \\ Inestability & 188 (37.45\%) & 50 (17.98\%) & 138 (16.61\%) & \(<\)0.001 & 7.317 (4.867, 11.000) & 0.718 \\ Reduced variability & 110 (21.9\%) & 38 (13.67\%) & 72 (32.14\%) & \(<\)0.001 & 2.992 (1.922, 4.656) & 0.592 \\ \hline \multicolumn{6}{l}{_Initial window_} \\ \hline Amplitude (ppm) & 6.12 (\(-\)1.97, 19.63) & 4.16 (\(-\)4.11, 13.11) & 12.32 (1.32, 24.38) & \(<\)0.001 & 1.023 (1.013, 1.034) & 0.631 \\ Duration (s) & 2.15 (\(-\)7.31, 14.44) & 1.31 (\(-\)4.71, 13.45) & 3.90 (\(-\)8.76, 23.55) & 0.136 & 1.008 (1.001, 1.015) & 0.538 \\ Drop (sg) & \(-\)1.41 (\(-\)10.84, 6.24) & \(-\)1.62 (\(-\)12.47, 8.11) & \(-\)0.78 (\(-\)8.72, 5.04) & 0.611 & 1.001(0.991, 1.012) & 0.513 \\ Slope (bpm/sg) & 0.29 (\(-\)0.24, 1.01) & 0.24 (\(-\)0.22, 0.59) & 0.64 (\(-\)0.29, 1.70) & \(<\)0.001 & 1.325 (1.154, 1.520) & 0.599 \\ Area (mm\({}^{2}\)) & 32.41 (\(-\)19.11, 99.12) & 17.20 (\(-\)25.10, 54.57) & 7.028 (\(-\)1.05, 163.74) & \(<\)0.001 & 1.004 (1.003, 1.006) & 0.657 \\ FHR (ppm) & 0 (0, 10) & 0 (0, 5) & 5 (0, 15) & & \(<\)0.001 & 1.006 (1.004, 1.008) & 0.651 \\ Saltatory Pattern & 88 (17.52\%) & 32 (11.51\%) & 56 (23.14\%) & \(<\)0.001 & 2.643 (1.506, 4.638) & 0.572 \\ \hline \end{tabular}
\end{table} 
Table 2: Descriptive characteristics and prediction ability of the parameters of the study. bpm: beats per minute; FHR: fetal heart rate.