Refining the Prediction and Prevention of Emergency Operative Deliveries with the Fetal Reserve Index

Improving the interpretation of electronic fetal monitoring: the fetal reserve index

Electronic fetal monitoring, particularly in the form of cardiotocography, forms the centerpiece of labor management. Initially successfully designed for stillbirth prevention, there was hope to also include prediction and prevention of fetal acidosis and its sequelae. With the routine use of electronic fetal monitoring, the cesarean delivery rate increased from <5% in the 1970s to >30% at present. Most at-risk cases produced healthy babies, resulting in part from considerable confusion as to the differences between diagnostic and screening tests. Electronic fetal monitoring is clearly a screening test. Multiple attempts have aimed at enhancing its ability to accurately distinguish babies at risk of in utero injury from those who are not and to do this in a timely manner so that appropriate intervention can be performed. Even key electronic fetal monitoring opinion leaders admit that this goal has yet to be achieved. Our group has developed a modified approach called the "Fetal Reserve Index" that contextualizes the findings of electronic fetal monitoring by formally including the presence of maternal, fetal, and obstetrical risk factors and increased uterine contraction frequencies and breaking up the tracing into 4 quantifiable components (heart rate, variability, decelerations, and accelerations). The result is a quantitative 8-point metric, with each variable being weighted equally in version 1.0. In multiple previously published refereed papers, we have shown that in head-to-head studies comparing the fetal reserve index with the American College of Obstetricians and Gynecologists' fetal heart rate categories, the fetal reserve index more accurately identifies babies born with cerebral palsy and could also reduce the rates of emergency cesarean delivery and vaginal operative deliveries. We found that the fetal reserve index scores and fetal pH and base excess actually begin to fall earlier in the first stage of labor than was commonly appreciated, and the fetal reserve index provides a good surrogate for pH and base excess values. Finally, the last fetal reserve index score before delivery combined with early analysis of neonatal heart rate and acid/base balance shows that the period of risk for neonatal neurologic impairment can continue for the first 30 minutes of life and requires much closer neonatal observation than is currently being done.

Uterine contraction frequency in the last hour of labor: how many contractions are too many?

OBJECTIVE

Increased frequency of uterine contractions is a component in the cluster of causal conditions that can lead to fetal hypoxia and acidosis and increase the risk for neonatal neurologic injury. For most international obstetrical societies, 5 contractions per 10 min averaged over 30 min is considered as the upper limit of normal uterine activity. We hypothesize that it might be safer to adopt an upper limit of 4 contractions per 10 min.

METHODS

We reviewed our 1970's research database containing 475 patients with closely monitored and well-documented labor and neonatal assessments that included cord blood (CB) pH, base excess (BE), and continuous recording of neonatal heart rate (NHR). Using data segregated by the proportion of the last hour before delivery when uterine contraction frequency (UCF) exceeded 4 and 5 contractions per 10 min respectively, we evaluated outcomes (CB BE, pH, Apgar scores at 1 min, the status of NHR at 16 min after birth, and the proportion of births that did not the result from normal spontaneous vaginal deliveries (NSVDs). ANOVA established relationships between UCF cutoffs and these outcomes. Our sample size is sufficiently large to provide the ability of UCF, per se, to accurately detect an alpha region of .05 88% of the time with an effect size of .15.

RESULTS

During the last hour prior to delivery, a UCF cutoff at 4 contractions per 10 min performed better than a UCF cutoff at 5 contractions per 10 min to enable the earlier identification of risks for abnormal outcomes. The longer UCF was increased, the worse were the outcomes that were measured, and the region >4 but ≤5 contractions identifies the beginnings of worsening conditions in a variety of measures of poor outcomes.

CONCLUSION

Lowering the recommended threshold for UCF from 5 to 4 contractions per 10-minute period as averaged over 30 min facilitates earlier detection of potentially compromised fetuses and is also an important contributor to a multicomponent contextualized approach to risk assessment.

Total intrapartum fetal reperfusion time (fetal resilience) and neonatal acidemia

OBJECTIVE

The main objective is to study the predictive capacity of intrapartum total fetal reperfusion (fetal resilience) by itself or in combination with other parameters as a predictor of neonatal acidemia.

STUDY DESIGN

A retrospective case-control study was carried out at the Miguel Servet University Hospital (Zaragoza, Spain) on a cohort of 5694 pregnant women between June 2017 and October 2018. Maternal, perinatal, and cardiotocographic records were collected. Two reviewers blindly described the monitors with the American College of Obstetricians and Gynecologists (ACOG) categorizations and parameters and the non-ACOG parameters. Neonatal acidemia was defined as pH <7.10. The parameters analyzed to predict acidemia were evaluated using the sensitivity for specificity 90% value, and the area under the receiver operating characteristic curve.

RESULTS

We recorded 192 infants with acidemia, corresponding to a global acidemia rate of 3.4%. Of these, 72 were excluded for lack of criteria, leaving 120 patients with arterial acidemia included in the study and 258 in the control group. The sensitivity (specificity 90%) of detection of acidemia was 42% for the ACOG III categorization (AUC, 0.524: 95% CI, 0.470-0.578), 24% for fetal reperfusion (AUC, 0.704: 95% CI, 0.649-0.759), 27% for total area of decelerations (AUC, 0.717: 95% CI, 0.664-0.771) and 50% for the multivariate model built from total reperfusion time (AUC, 0.826: 95% CI, 0.783-0.869). The total reperfusion time corresponding to a false negative rate of 10% is 23.75 min, with 28% of fetuses above this time. The AUC and sensitivity for a false negative rate of 10% are equivalent for deceleration area and time of reperfusion (p = .504).

CONCLUSION

The total reperfusion time (fetal resilience) and total deceleration area are non-ACOG parameters with a good predictive ability for neonatal acidemia, higher than the ACOG III classification and without statistical differences between them. The discrimination ability of total reperfusion time can be improved using a multivariate model. As a cutoff for its use we suggest 23.75 min in 30 min corresponding to an acidemic classification rate of 90%. New parameters in combination with other maternal, obstetrics, or fetal variables, are required for the interpretation of fetal well-being.

Mid forceps did not cause "compromised babies" - "compromise" caused forceps: an approach toward safely lowering the cesarean delivery rate

OBJECTIVE

Over 5 decades, Cesarean Delivery rates (CDR) have risen 6-fold while vaginal operative deliveries [VODs] decreased from >20% to ∼3%. Poor outcomes (HIE and cerebral palsy) haven't improved. Potentiating the virtual abandonment of forceps (F), particularly midforceps (Mid), were allegations about various poor neonatal outcomes. Here, we evaluate VOD and CDR outcomes controlling for prior fetal risk metrics (PR) ascertained an hour before birth.

METHODS

Our 45-year-old database from a labor research unit of moderate/high risk laboring patients (288 NSVDs, 120 Lows, 30 Mids, and 32 CDs) had multiple fetal scalp samples for base excess (BE), pH, cord blood gases (CB), and umbilical artery bloods. ANOVA established relationships between birth methods and outcomes (Cord blood BE and pH and 1 and 5 min Apgar scores); correlations, and two-step multiple regression assessed PR for delivery method and neonatal outcomes. The main outcome measures were correlations of outcome measures with fetal scalp sample BE and pH up to an hour before delivery and fetal reserve index scores scored concurrently.

RESULTS

NSVDs had the best immediate neonatal outcomes with significantly higher CB pH and BE as compared to forceps and CDs. However, controlling for PR revealed: (1) PR at 1 h before delivery correlated with delivery mode, i.e. the decrements in outcomes were already present before the delivery was performed; and (2) The presumed deleterious effects of interventional deliveries, per se, were significantly reduced, and (3) Fetal Reserve Index predicted neonatal outcomes better than fetal scalp sample BE, pH, or delivery mode.

CONCLUSION

The historical belief that MF deliveries caused poorer outcomes than NSVDs seems mostly backwards. Appreciating PR's impact on delivery routes, and when appropriate, properly performing VODs could safely reduce CDR. If our approach lowered CDR by only ∼2%, in the United States about 80,000 CDs might be avoided, saving ∼$750 Million yearly. In the post pandemic world, safely apportioning medical expenses will be even more critical than previously.

Earlier and improved screening for impending fetal compromise

OBJECTIVE

The use of pH and base excess (FSSPHBE) from fetal scalp sampling (FSS) was abandoned when cardiotocography (CTG) was believed to be sufficiently accurate to direct patient management. We sought to understand the fetus' tolerance to stress in the 1st stage of labor and to develop a better and earlier screening test for its risk for developing acidosis. To do so, we investigated sequential changes in fetal pH and BE obtained from FSS in the 1st stage of labor as part of a research protocol from the 1970s. We then examined the utility of multiple of the median (MoM's) conversion of BE and pH values, and the capacity of Fetal Reserve Index (FRI) scores to be a proxy for such changes. We then sought to examine the predictive capacity of 1st stage FRI and its change over the course of the first stage of labor for the subsequent development of acidosis risk in the 2nd stage of labor.

METHODS

Using a retrospective research database evaluation, we evaluated FSSPHBE data from 475 high-risk parturients monitored in labor and their neonates for 1 h postpartum. We categorized specimens according to cervical dilatation (CxD) at the time of FSSPHBE and developed non-parametric, multiples of the median (MOMs) assessments. FRI scores and their change over time were used as predictors of FSSPHBE. Our main outcome measures were the changes in BE and pH at different cervical dilatations (CxD) and acidosis risk in the early 2nd stage of labor.

RESULTS

FSSPHBE worsens over the course of the 1st stage. The implications of any given BE are very different depending upon CxD. At 9 cm, -8 Mmol/L is 1.1 MOM; at 3 cm, it would be 2.0 MOM. The FRI level and its trajectory provide a 1st stage screening tool for acidosis risk in the second stage.

CONCLUSIONS

Fetal acid-base balance ("reserve") deteriorates beginning early in the 1st stage of labor, irrespective of whether the fetus reaches a critical threshold of concern for actual acidosis. The use of MoM's logic improves appreciation of such information. The FRI and its trajectory reasonably approximate the trajectory of the FSSPHBE and appears to be a suitable screening test for early deterioration and for earlier interventions to keep the fetus out of trouble rather than wait until high risk status develops.

Combined prenatal and postnatal prediction of early neonatal compromise risk

OBJECTIVE

Electronic fetal monitoring/cardiotocography (EFM) is nearly ubiquitous, but almost everyone acknowledges there is room for improvement. We have contextualized monitoring by breaking it down into quantifiable components and adding to that, other factors that have not been formally used: i.e. the assessment of uterine contractions, and the presence of maternal, fetal, and obstetrical risk factors. We have created an algorithm, the Fetal Reserve Index (FRI) that significantly improves the detection of at-risk cases. We hypothesized that extending our approach of monitoring to include the immediate newborn period could help us better understand the physiology and pathophysiology of the decrease in fetal reserve during labor and the transition from fetal to neonatal homeostasis, thereby further honing the prediction of outcomes. Such improved and earlier understanding could then potentiate earlier, and more targeted use of neuroprotective attempts during labor treating decreased fetal reserve and improving the fetus' transition from fetal to neonatal life minimizing risk of neurologic injury.

STUDY DESIGN

We have analyzed a 45-year-old research database of closely monitored labors, deliveries, and an additional hour of continuous neonatal surveillance. We applied the FRI prenatally and created a new metric, the INCHON index that combines the last FRI with umbilical cord blood and 4-minute umbilical artery blood parameters to predict later neonatal acid/base balance. Using the last FRI scores, we created 3 neonatal groups. Umbilical cord and catheterized umbilical artery bloods at 4, 8, 16, 32, and 64 minutes were measured for base excess, pH, and PO₂. Continuous neonatal heart rate was scored for rate, variability, and reactivity.

RESULTS

Neonates commonly do not make a smooth transition from fetal to postnatal physiology. Even in low risk babies, 85% exhibited worsening pH and base excess during the first 4 minutes; 34% of neonates reached levels considered at high risk for metabolic acidosis (≤-12 mmol/L) and neurologic injury. Neonatal heart rate commonly exhibited sustained, significant tachycardia with loss of reactivity and variability. One quarter of all cases would be considered Category III if part of the fetal tracing. Our developed metrics (FRI and INCHON) clearly discriminated and predicted low, medium, and high-risk neonatal physiology.

CONCLUSIONS

The immediate neonatal period often imposes generally unrecognized risks for the newborn. INCHON improves identification of decreased fetal reserve and babies at risk, thereby permitting earlier intervention during labor (intrauterine resuscitation) or potentially postnatally (brain cooling) to prevent neurologic injury. We believe that perinatal management would be improved by routine, continuous neonatal monitoring - at least until heart rate reactivity is restored. FRI and INCHON can help identify problems much earlier and more accurately than currently and keep fetuses and babies in better metabolic shape.

The Fetal Reserve Index Significantly Outperforms ACOG Category System in Predicting Cord Blood Base Excess and pH: A Methodological Failure of the Category System

OBJECTIVE

Electronic fetal monitoring (EFM) has been used extensively for almost 50 years but performs poorly in predicting and preventing adverse neonatal outcome. In recent years, the current "enhanced" classification of patterns (category I-III system [CAT]) were introduced into routine practice without corroborative studies, which has resulted in even EFM experts lamenting its value. Since abnormalities of arterial cord blood parameters correlate reasonably well with risk of fetal injury, here we compare the statistical performance of EFM using the current CAT system with the Fetal Reserve Index (FRI) for predicting derangements in base excess (BE), pH, and pO₂ in arterial cord blood.

METHODS

We utilized a research database of labor data, including umbilical cord blood measurements to assess patients by both worst CAT and last FRI classifications. We compared these approaches for their ability to predict BE, pH, and pO₂ in cord blood.

RESULTS

The FRI showed a clear correlation with cord blood BE and pH with BE being more highly correlated than pH. The CAT was much less predictive than FRI (P < .05). The CAT II cases had FRI scores across the spectrum of severity of FRI designations and as such provide little clinical discrimination. The PO₂ was not discriminatory, in part, because of neonatal interventions.

CONCLUSIONS

The Fetal Reserve Index (FRI) provides superior performance over CAT classification of FHR patterns in predicting the BE and pH in umbilical cord blood. Furthermore, the CAT system fails to satisfy multiple fundamental principles required for successful screening programs. Limitations of CAT are further compounded by assumptions about physiology that are not consistent with clinical observations.