Gynecol, obstet. Invest. 10: 119- 126 (1979)
Fetal Heart Rate in the Second Stage of Labour Method of Interpretation and Parameters of the New-Born M. Van Lierde, X. De Muylder and K. Thomas Physiology of Human Reproduction Research Unit, Department of Obstetrics and Gynecology, University of Louvain, Brussels
Key Words.
Fetal heart rate • Delivery • Apgar • Acidosis
Abstract. The authors present a protocol for the interpretation of the fetal heart rate during the second stage of labour (limited to the last 30 min before delivery). The FHR recordings were grouped according to five classes of increasing pathological significance. Good correlations were obtained between these classifications and the Apgar score as well as the umbilical artery pH.
Many fetal risk factors appear with maximum intensity during the period of expulsion. The uterine contractions exceed an intensity of 80 mm Hg, a level above which the arterial utero-placental intake into the intervillous space is probably interrupted. The lapse of time between contractions is sometimes less than 2 min, which is the necessary delay for the fetus to recuperate from hypoxia. The abdominal pressures of the mother’s expulsive efforts have to be added to the harmful influence of uterine pressures on placental circulation and fetal oxygenation. Head compression is intense after the rupture of the mem branes and during engagement of the fetal head. Furthermore, the mother often lies in the supine position, which favours the vena cava syndrome and Poseiro’s syndrome. At the end of labour, the woman is generally in metabolic acidosis, complicated during expulsion by long-lasting apnoeas. For all the above reasons, the second stage of labour is a period of high fetal risk, during which a great number of changes in the fetal heart rate (FHR) can be observed.
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Introduction
120
Van Lierde/De Muyldcr/Thomas
Up to now only a few authors have studied the FHR in the second stage of labour. The aim of the present study is to elaborate a simple and practical classification of the FHR during the last 30 min of this stage.
Material and Methods
543 vaginal deliveries were studied; 528 of these (97%) were accompanied by con tinuous cardiotocographic monitoring. 356 deliveries (65%) gave a cardiotocographic re cording of good technical quality until the birth, and allow a valid interpretation. The period which was studied was expulsion or second stage of labour. When this stage was long, the analysis was limited to the last 30 min. A protocol for the interpretation of the cardiotocographic records using five classes was established: class I: strictly normal; class II: non-specifically abnormal; class III: suspect; class IV: pathological; class V: highly pathological. This classification protocol was based on the analysis of the following three parameters: basal FHR, long-term variability and deceleration (table 1). The long-term variability agrees with Hammacher and Werners’ (1968) different types of oscillations. The decelerations are simultaneous or residual type, according to Sureau et al.'s (1970) classification. Class / concerns strictly normal traces: basal FHR between 120 and 150, oscillations af type I or II and absence of decelerations (4.2% of deliveries). Class II includes FHRs which show non-specific abnormalities but which are not considered pathological during the second stage of labour: tachycardia, saltatory rhythm (type III oscillations), slight simultaneous decelerations (nadir generally above 100 bpm; fig. 1) (34.9% of deliveries). Class III groups traces showing only one of the following abnormalities: slight brady cardia (100-120 bpm), silent rhythm (0 type), simultaneous (nadir below 100 bpm) or residual decelerations (fig. 2) (40.2% of deliveries).
Table I. Classification of FHR during the second stage of labour
I
II
III
IV
V
Basal FHR
120-150
>120
Variability
I-II
I-II-I1I
80-100 or 2 crit.
Fetal Heart Rate in the Second Stage of Labour Method of Interpretation and Parameters of the New-Born M. Van Lierde, X. De Muylder and K. Thomas Physiology of Human Reproduction Research Unit, Department of Obstetrics and Gynecology, University of Louvain, Brussels
Key Words.
Fetal heart rate • Delivery • Apgar • Acidosis
Abstract. The authors present a protocol for the interpretation of the fetal heart rate during the second stage of labour (limited to the last 30 min before delivery). The FHR recordings were grouped according to five classes of increasing pathological significance. Good correlations were obtained between these classifications and the Apgar score as well as the umbilical artery pH.
Many fetal risk factors appear with maximum intensity during the period of expulsion. The uterine contractions exceed an intensity of 80 mm Hg, a level above which the arterial utero-placental intake into the intervillous space is probably interrupted. The lapse of time between contractions is sometimes less than 2 min, which is the necessary delay for the fetus to recuperate from hypoxia. The abdominal pressures of the mother’s expulsive efforts have to be added to the harmful influence of uterine pressures on placental circulation and fetal oxygenation. Head compression is intense after the rupture of the mem branes and during engagement of the fetal head. Furthermore, the mother often lies in the supine position, which favours the vena cava syndrome and Poseiro’s syndrome. At the end of labour, the woman is generally in metabolic acidosis, complicated during expulsion by long-lasting apnoeas. For all the above reasons, the second stage of labour is a period of high fetal risk, during which a great number of changes in the fetal heart rate (FHR) can be observed.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/24/2018 8:11:42 PM
Introduction
120
Van Lierde/De Muyldcr/Thomas
Up to now only a few authors have studied the FHR in the second stage of labour. The aim of the present study is to elaborate a simple and practical classification of the FHR during the last 30 min of this stage.
Material and Methods
543 vaginal deliveries were studied; 528 of these (97%) were accompanied by con tinuous cardiotocographic monitoring. 356 deliveries (65%) gave a cardiotocographic re cording of good technical quality until the birth, and allow a valid interpretation. The period which was studied was expulsion or second stage of labour. When this stage was long, the analysis was limited to the last 30 min. A protocol for the interpretation of the cardiotocographic records using five classes was established: class I: strictly normal; class II: non-specifically abnormal; class III: suspect; class IV: pathological; class V: highly pathological. This classification protocol was based on the analysis of the following three parameters: basal FHR, long-term variability and deceleration (table 1). The long-term variability agrees with Hammacher and Werners’ (1968) different types of oscillations. The decelerations are simultaneous or residual type, according to Sureau et al.'s (1970) classification. Class / concerns strictly normal traces: basal FHR between 120 and 150, oscillations af type I or II and absence of decelerations (4.2% of deliveries). Class II includes FHRs which show non-specific abnormalities but which are not considered pathological during the second stage of labour: tachycardia, saltatory rhythm (type III oscillations), slight simultaneous decelerations (nadir generally above 100 bpm; fig. 1) (34.9% of deliveries). Class III groups traces showing only one of the following abnormalities: slight brady cardia (100-120 bpm), silent rhythm (0 type), simultaneous (nadir below 100 bpm) or residual decelerations (fig. 2) (40.2% of deliveries).
Table I. Classification of FHR during the second stage of labour
I
II
III
IV
V
Basal FHR
120-150
>120
Variability
I-II
I-II-I1I
80-100 or 2 crit.
