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EP-4007527-B1 - APPARATUS FOR INDICATING A RISK OF NEUROLOGICAL INJURY TO A HUMAN FETUS DURING AND BEFORE LABOR

EP4007527B1EP 4007527 B1EP4007527 B1EP 4007527B1EP-4007527-B1

Inventors

  • EVANS, MARK

Dates

Publication Date
20260506
Application Date
20200803

Claims (10)

  1. An apparatus (10, 10', 110) for indicating a risk of neurological injury to a human fetus before or during labor, the apparatus (10, 10', 110) comprising: at least one computer (20, 20') operative to: receive input signals indicative of at least a first set of concurrent clinical parameters indicative of a present level of risk for neurological injury to the fetus; determine at a first period in time during or before the first stage of labor a present level of risk to the fetus for neurological injury based on the first set of concurrent clinical parameters, wherein the determined present level of risk is expressed as a numerical value, herein referred to as the first FRI value; characterised in that the at least one computer (20, 20') is programmed with a dataset comprising a population of FRI values established at the same period in time during or before the first stage of labor as the first period and is operative to determine a multiple of the median, MoM, for the first FRI value by dividing the first FRI value by the median FRI value of the dataset; and provide an output (50) indicating a risk for neurological injury when the determined MoM of the first FRI value is a predefined multiple of the median FRI value.
  2. The apparatus (10, 10', 110) of claim 1, wherein the at least one computer (20, 20') is further operative to: receive inputs indicating base excess, BE, values for the fetus at least second and third periods in time during the first stage of labor, wherein the third period in time is later than the second period in time; determine a rate of drop for the BE values at the second and third periods in time; and provide an output (50) indicating a risk for neurological injury when the BE values at the second and third periods in time reflect a rate of drop greater than a predefined value.
  3. The apparatus (10, 10', 110) of claim 2, wherein the second and third periods in time during labor are each characterized by a cervical dilatation of less than 10 cm.
  4. The apparatus (10, 10', 110) of claim 1, wherein: the first set of concurrent clinical parameters comprise (a) FHR, (b) baseline FHR variability, (c) FHR accelerations, (d) FHR decelerations, and (e) maternal uterine activity; and wherein the at least one computer (20, 20') is operative to determine at the first period in time whether each concurrent clinical parameter (a) through (e) independently exhibits at least one non-reassuring characteristic, and to transform the number of the concurrent clinical parameters (a) through (e) that simultaneously, independently exhibit at least one non-reassuring characteristic into the first FRI value.
  5. The apparatus (10, 10', 110) of claim 1, wherein the at least one computer (20, 20') is further operative to: determine at a second period in time during or before the first stage of labor, later than the first period in time, a present level of risk to the fetus for neurological injury based on the first set of concurrent clinical parameters, wherein the determined present level of risk is expressed as a second FRI value; determine a rate of drop from the first FRI value to the second FRI value; determine a MoM for the rate of drop by dividing the rate of drop by the median rate of drop of a dataset comprising a population of rates of drop for FRI values established at the same periods in time during or before the first stage of labor as the first and second periods; and provide an output (50) indicating a risk for neurological injury when the determined rate of drop from the first FRI value to the second FRI value is at least a predetermined rate of drop.
  6. The apparatus (10, 10', 110) of claim 5, wherein the first period in time during labor is characterized by a cervical dilatation of between 0-3 cm.
  7. The apparatus (10, 10', 110) of any of claims 5 or 6, wherein the second period in time during labor is characterized by a cervical dilatation of less than or equal to 10 cm or up to an hour later than the first time period.
  8. The apparatus (10, 10', 110) of any of claims 5-7, wherein the risk of neurological injury to the fetus is indicated when the rate of drop is 46% or greater.
  9. The apparatus (10, 10', 110) of any of claims 5-8, wherein: the first set of concurrent clinical parameters comprise (a) FHR, (b) baseline FHR variability, (c) FHR accelerations, (d) FHR decelerations, and (e) maternal uterine activity; and wherein the at least one computer (20, 20') is operative to determine at the first period in time whether each concurrent clinical parameter (a) through (e) independently exhibits at least one non-reassuring characteristic, and to transform the number of the concurrent clinical parameters (a) through (e) that simultaneously, independently exhibit at least one non-reassuring characteristic into the first FRI value.
  10. The apparatus (10, 10', 110) of any of claims 5-9 wherein the at least one computer (20, 20') is further operative to: provide an output indicating the existence of neurological injury to the fetus when the MoM for the rate of drop is a predefined MoM rate of drop.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is related to, and claims the benefit of priority from, United States Provisional Application Serial No. 62/881,701, filed 1 August 2019. FIELD OF THE INVENTION The present invention pertains to the field of obstetrics and, more specifically, to methods and apparatus for reducing the risk of neurological injury to a human fetus during and before labor. BACKGROUND Current methods for assessing fetal health and predicting risk of neurologic compromise using the American College of Obstetricians and Gynecologist's (ACOG) "Category System" are very poor, missing as much as 50% of cerebral palsy (CP) cases. Its use has led to significant increases in the Cesarean Delivery Rate (CDR), with little to no impact on reducing severe complications such as CP. The statistical performance metrics of the Category System violate essentially all of the key standard principles required for an effective screening program. ACOG's Category III, which is the point of required action to deliver, or at least treat, the fetus is so far to the right on the distribution curve of values that it has a high positive predictive value for damage - much of which may have already occurred. It also has a very high and unacceptable false negative rate - with 50% of serious cases missed (as reported in multiple publications). Conversely, ACOG's Category II, which is defined as having "concern" (but for which there is no clearly accepted mandated action), is so far to the left on the distribution curve of cases that it is reached by up to 75% of all patients. This renders Category II useless as a screening test. Electronic fetal monitoring (EFM) was introduced into practice in the late 1960's in an attempt to permit timely intervention (e.g., expedited delivery by cesarean delivery, use of vacuum or forceps, etc.) in situations in which the fetus appears to either be presently compromised already or will be so imminently. EFM has been widely adopted and used, for decades past and to the present, in the vast majority of births in the United States. The premise of EFM is the recognition of asphyxia related to metabolic acidemia. The response to fetal heart rate (FHR) patterns is predicated on the identification and "rescue" of the asphyxiated fetus, hopefully, before it has suffered damage. Traditionally, when EFM data demonstrate an overall impression of "reassurance," labor is allowed to continue, with intervention being reserved for situations when EFM is abnormal, indicative of significant asphyxia (from metabolic acidosis), or an acute emergency arises (e.g., fetal bradycardia). Such interpretations are often very subjective; even distinguished experts often disagree as to the significance of individual patterns. In an improvement of the conventional means for interpreting EFM data and improving fetal outcomes in labor and delivery, the inventor hereof discloses in United States Patent 9,131,860 (the disclosure of which is incorporated herein by reference in its entirety) an apparatus for identifying the level of fetal risk during labor. The apparatus includes at least one computer operative to receive input signals indicative of at least FHR and maternal uterine activity in a patient, the at least one computer further operative (i) to determine from the FHR at least baseline FHR variability, FHR accelerations, and FHR decelerations, and (ii) to determine when each of at least (a) FHR, (b) baseline FHR variability, (c) FHR accelerations, (d) FHR decelerations, and (e) maternal uterine activity exhibit at least one non-reassuring characteristic from among a plurality of pre-defined non-reassuring characteristics for at least the parameters (a) through (e). The at least one computer is further operative to (iii) receive user-inputs indicative of the presence in the patient of one or more antecedent clinical parameters which elevate the level of fetal risk during labor, and (iv) to determine at a given point in time during labor a present level of risk to the fetus which takes into account only: the total number of the one or more antecedent clinical parameters which elevate the level of fetal risk during labor; and the total number of the parameters (a) through (e) that each simultaneously, independently exhibit at least one of the non-reassuring characteristics at the given point in time during labor. This invention has been demonstrated to yield consistent assessment of EFM data and, consequently, consistent identification of fetuses at risk for neurological injury. This Fetal Reserve Index (FRI) provides a more meaningful alternative to ACOG's Category System. FRI combines various risk factors and the presence of increased uterine contractions during labor to produce a statistically significant prediction of fetal risk for cerebral palsy. FRI's indicators of risk are valid much earlier in the pathophysiology than ACOG's Category System. By identifying potential concerns earlier