Clinical significance of fetal heart rate patterns during labor I I. Late decelerations

LUIS Chicago,





Among a population of high-risk patients in labor who bud continuous “direct” electronic monitoring, 147 presented late decelerations and 598 had no decelerations at the time the jirst stage was completed, or a cesarean section decided upon. A variety of clinical aspects of mothr and fetus were analyzed, considering some alterations observed in the FHR pattern. Apgar scores were lower among decelerations, and there was a negative correlation between thPse two. Maternal pathology, other than PRM, was higher among decelerations and these required enhancement more often. There was very high association with tachycardia, saltatory, and fixed baseline among decelerations, and these infants were very often distressed and born depressed. Within the group of decelerations, small fetuses had lower Apgar scores. There was a negative correlation between number of decelerations and Apgar score. The small fetuses had a high incidence of tachycardia and fixed baseline, salt&my being almost absent. Their neonatal outcome was poor. A comparison offetal response to distress was done considering age of gestation (premature, term, and postmature) and found to be different. The mechanisms involved in late deceleration are discussed, reviewing th p&i&d experimental work. When interpreting FHR patterns, age of gestation should be one of thP most important considerations.

morbidity and mortality rates. Only very few studies have been published supporting that premise30* 3 but there is sufficient indirect evidence which indicates that it is only a matter of time before irrefutable proof will be obtained to substantiate that principle.3* ‘, IiS ‘*, “* “* 2g* 33 Needless to say, the improved results come from institutions staffed by individuals who are pioneers in this field and, therefore, highly trained in the proper interpretation of the recordings. It is probably fair to say that one should not expect the same good results from institutions staffed by physicians with more limited experience. The reasons for the less than ideal results may be many, but among them the lack of proper interpretation of fetal heart rate changes should be considered one of the most important. It was decided to analyze the material accumulated at the Chicago Lying-in Hospital with the desire to contribute the experience of a university center caring for a large number of high-risk patients and where young house officers receive their training. This report is thus not representative of what one might expect from a maternity service of a community hospital dedica.ted only to patient care.

THE ADEQUATE interpretation of fetal heart rate changes during labor has not kept pace with the rapid acceptance of intrapartum fetal and maternal monitoring. It is not an overstatement to say that nearly any maternity unit in this country makes available to its attendings the use of electronic monitoring equipment to supervise the mother and fetus during labor, but most of those using the equipment do not have the experience required for adequate evaluation of the records, and thus cannot make the most appropriate decisions. The popularity of intrapartum monitoring, either chemical or electronic, is based on the assumption that it may help to lower the perinatal From thp Chicago Chicago.



This work was supported in pati Spray Memorial Foundation. Presented by invitation American Gynecological April 9-12, 1975.


by a grant

at the Ninety-eighth Society, Coronado,


of the

Meeting Calfofornia,

of the

Reprint requests: Dr. Luis A. Cibils, 5841 Malykznd Ave.,


*Maq Campau and Gynecology.

Illinois Ryerson

60637. Professor

of Obstetrics 473



Fig. 1. Term gestation admitted for induction of labor. Continuous 100 minute recordings of FHR (upper channel) and intrauterine pressure (lower channel). In this and subsequent recordings the scale for FHR (beats per minute) is marked on the ordinates and the scale for UC is 20 mm. Hg per horizontal line, in the abscissa. The time scale is 1 minute between the heavier vertical lines. In the upper part of the recording the good UC stimulated by 5 mu. per minute of oxytocin, and recurring every 3.5 to 4 minutes, produced mild late decelerations on a baseline with normal rapid oscillations. When the frequency of UC increased to less than every 3 minutes the magnitude of the FHR deceleration and the recovery time increased. The baseline reached progressively higher levels between decelerations. In the lower part of the recording it is shown when oxytocin was discontinued and the subsequent decrease in frequency of UC (there are three unrecorded because of obstructed catheter). The effect of FHR shows that the baseline reached a stable but very high level and that it became “fixed,” still responding with severe decelerations to the few mild UC. Rapid cesarean section revealed a concealed unexpected abruptio placentae. The infant had a good Apgar score and did well.

Matarlals and methods From



to December,




in labor had continuous uterine contractions (UC) and fetal heart rate (FHR) monitoring in the Section of Maternal and Fetal Medicine of the Chicago Lying-in Hospital.








single direct and


in cephalic

or “internal” fetal


monitoring electrode),


with a minimum of 60 minutes of recording prior to complete dilatation or the decision to perform a cesarean section, were included in this study. A total of 1,304








programmed for analyses of correlations between UC and FHR changes and various clinical conditions. The

description of clinical material has previously been rep0rted.O Briefly summarized, it is as follows. Age, parity, age of gestation, pathologic condition (hypertension, premature rupture of membranes, diabetes, heart disease, Rh sensitization, premature labor, prolonged pregnancy, abruptio placentae, desultory labor, etc.), type of labor, presence of fetal distress, type of anesthesia, and type of delivery were recorded from







at 1 and


minutes, condition of the cord (free, around limbs or shoulder, knots, velamentous insertion, very short, or too long), infant and placental weight, and neonatal evolution until discharge were noted from the fetal chart.





Table I. Average clinical “late” decelerations

FHR patterns during labor. II 475

data of patients

who presented

No deceledon

Patient’s age Gestational age Minutes recording No. contractions No. decelerations Apgar at 1 minute Apgar at 5 minutes Fetal weight Placental weight F/P ratio


no FHR decelerations







252.0 87.0

8.1 9.5 3,236.0

and those who had

(14 7)

232. 77.0 33.6 6.8 8.7 3,101.o







0.66 0.23 17.60 5.90 2.30

Clinical significance of fetal heart rate patterns during labor. II. Late decelerations.

Among a population of high-risk patients in labor who had continuous "direct" electronic monitoring, 147 presented late decelerations and 598 had no d...
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