Impaired validity of the new FIGO and Swedish CTG classification templates to identify fetal acidosis in the first stage of labor

Is the fetus fit for labor? Introducing fast-and-frugal trees (FFTrees) to simplify triage of women for STAN monitoring: An interobserver agreement comparison with traditional classification

INTRODUCTION

It is a shortcoming of traditional cardiotocography (CTG) classification table formats that CTG traces are frequently classified differently by different users, resulting in poor interobserver agreements. A fast-and-frugal tree (FFTree) flow chart may help provide better concordance because it is straightforward and has clearly structured binary questions with understandable "yes" or "no" responses. The initial triage to determine whether a fetus is suitable for labor when utilizing fetal ECG ST analysis (STAN) is very important, since a fetus with restricted capacity to respond to hypoxic stress may not generate STAN events and therefore may become falsely negative. This study aimed to compare physiology-focused FFTree CTG interpretation with FIGO classification for assessing the suitability for STAN monitoring.

MATERIAL AND METHODS

A retrospective study of 36 CTG traces with a high proportion of adverse outcomes (17/36) selected from a European multicenter study database. Eight experienced European obstetricians evaluated the initial 40 minutes of the CTG recordings and judged whether STAN was a suitable fetal surveillance method and whether intervention was indicated. The experts rated the CTGs using the FFTree and FIGO classifications at least 6 weeks apart. Interobserver agreements were calculated using proportions of agreement and Fleiss' kappa (κ).

RESULTS

The proportions of agreement for "not suitable for STAN" were for FIGO 47% (95% confidence interval [CI] 42%-52%) and for FFTree 60% (95% CI 56-64), ie a significant difference; the corresponding figures for "yes, suitable" were 74% (95% CI 71-77) and 70% (95% CI 67-74). For "intervention needed" the figures were 52% (95% CI 47-56) vs 58% (95% CI 54-62) and for "expectant management" 74% (95% CI 71-77) vs 72% (95% CI 69-75). Fleiss' κ agreement on "suitability for STAN" was 0.50 (95% CI 0.44-0.56) for the FIGO classification and 0.57 (95% CI 0.51-0.63) for the FFTree classification; the corresponding figures for "intervention or expectancy" were 0.53 (95% CI 0.47-0.59) and 0.57 (95% CI 0.51-0.63).

CONCLUSIONS

The proportion of agreement among expert obstetricians using the FFTree physiological approach was significantly higher compared with the traditional FIGO classification system in rejecting cases not suitable for STAN monitoring. That might be of importance to avoid false negative STAN recordings. Other agreement figures were similar. It remains to be shown whether the FFTree simplicity will benefit less experienced users and how it will work in real-world clinical scenarios.

Sporadic accelerations during labor strongly indicate normal pH, whereas periodic accelerations do not: a case-control study

PURPOSE

To determine the association between the occurrence of sporadic and periodic fetal heart rate accelerations during labor and acidemia at birth.

MATERIALS AND METHODS

This is a case-control study of fetal heart rate patterns from 364 neonates with acidemia at birth (cord blood pH <7.05 at vaginal birth, or pH <7.10 at birth after first stage cesarean delivery) and 731 controls with pH ≥7.15. The last 30-60 min of the cardiotocographic traces before birth from the neonates born with acidemia and from the corresponding stage in labor for the controls were scrutinized. Odds ratios (OR) with 95% confidence interval for acidemia at birth were determined.

RESULTS

During the first stage, ≥2 sporadic accelerations were present in 16% of cases and 78% of controls; OR for acidemia (compared to 0-1 accelerations) 0.05 (0.02-0.10). In the second stage, the corresponding rates were 13% and 60%, OR 0.09 (0.06-0.14). Isolated periodic accelerations were infrequent. A weak negative association between ≥2 periodic accelerations and acidemia (compared with 0-1 accelerations) was found in the second stage, OR 0.51 (0.30-0.86), but was not significant in the first stage, OR 0.24 (0.04-1.4). Even among fetuses with normal fetal heart rate variability (5-25 beats per minute) the occurrence of less than two sporadic accelerations was associated with an increased risk of acidemia, OR 10.3 (7.2-14.8).

CONCLUSIONS

Sporadic accelerations indicate a very low probability of acidosis but are absent in 40% of fetuses with normal pH during a 30-60 min second-stage recording.

CTG interpretation templates affect residents' decision making

OBJECTIVE

To study whether a revision of CTG guidelines and educational program influenced the perceived need for intervention by residents in obstetrics and gynecology. A secondary aim was to study the sensitivity and specificity of the classification pathological after classification by residents using two different guidelines in identifying neonates with acidemia.

STUDY DESIGN

Cardiotocograms, CTGs, from 223 neonates with acidemia at birth (cord blood pH < 7.05 at vaginal birth or second stage cesarean, or pH < 7.10 at first stage cesarean) were included, as well as 223 CTGs from neonates with cord blood pH ≥ 7.15. Two separate groups of residents, who each were educated in and had clinical experience only from either of the two different guidelines, SWE09 and SWE17, classified the patterns according to the at the time current template and judged whether the patterns indicated an intervention. Sensitivity, specificity, and agreement were calculated.

RESULTS

Residents using SWE09 found indication to intervene in a higher proportion of neonates with acidemia (84.8%) than residents using SWE17 (75.8%; p = 0.002), as well as in cases without acidemia (29.6% vs 22.4%; p = 0.038). Among residents using SWE09 the perceived need for intervention had a sensitivity of 85% and a specificity of 70% to identify acidemia. With SWE17 the corresponding rates were 76% and 78%. The sensitivity to identify neonates with acidemia by classification pathological was 91% with SWE09 and 72% with SWE17. The specificity was 53% and 76% respectively. The agreement rate between perception of indication to intervene and classification pathological using the SWE09 was κ 0.73, moderate, and with the SWE17 κ 0.77, moderate. The agreement on subjective perception of necessity to intervene between users of the two templates was weak to moderate, κ 0.60, and on classification pathological weak, κ 0.47.

CONCLUSION

The perceived need for intervention by residents interpreting CTGs was significantly affected by the guidelines in use. The difference in decisions were less pronounced than the difference in classification. The sensitivity for both perceived need for intervention and for classification pathological to identify acidosis was higher with SWE09, and the specificity higher with SWE17, when assessed by the two comparable groups of residents.

A Review on Magnetic Induction Spectroscopy Potential for Fetal Acidosis Examination

Fetal acidosis is one of the main concerns during labor. Currently, fetal blood sampling (FBS) has become the most accurate measurement of acidosis detection. However, it is invasive and does not provide a real time measurement due to laboratory procedures. Delays in diagnosis of acidosis have caused serious injury to the fetus, especially for the brain and the heart. This paper reviews the new technique in diagnosis of acidosis non-invasively. Magnetic Induction Spectroscopy (MIS) has been proposed to be a new device for acidosis detection in recent years. This paper explains the basic principle of MIS and outlines the design specifications and design considerations for a MIS pH probe. It is expected that readers will gain a basic understanding of the development of a MIS pH probe from this review.