Fetal heart rate patterns in labors with intact and with ruptured membranes

SCHWARCZ, R.; ALTHABE, O.; BELITZKY, R.; LANCHARES, J.L.; ALVAREZ, R.; BERDAGUER, P.; CAPURRO, H.; BELIZÁN, J.M.; SABATINO, J.H.; ABUSLEME, C.; CALDEYROBARCIA, R.

JOURNAL OF PERINATAL MEDICINE

WALTER DE GRUYTER & CO

Año: 1973 vol. 1 p. 153 - 165

0300-5577

In previous papers [1, 6] it was reported that the rupture of membranes facilitates the produc­ tion of type 1dips in the fetal heart rate (FHR) tracing. This statement is based on the effect of amniotomy on FHR records [6] and also on the quantitative study of a group of 26 monitored labors induced with oxytocin [1], in which mem­ branes were artificially ruptured when cervical dilatation was between 4 and 6 cm: The incidence of type I dips was significantly higher after amniotomy than before this procedure. The type 1 dips recorded after rupture of the membrane were attributed to the uneven compression and deformation of the fetal head, or to occlusion of the umbilical vessels during uterine con­ tractions [1, 6, 19]. 1t was postulated that both effects of uterine contractions were facilitated by the rupture of the bag of waters and corre­ sponding loss of amniotic fluid around the fetal head or the umbilical cord. The design of this previous study [1] did not allow the ana­ lysis of the effects of amniotomy independently from the infl.uence of the engagement of the fetal head in the pelvis. The head was usually not engaged from the beginning of labor _until the time of amniotomy, whereas it was engaged during most of the period elapsing after rupture of membranes until deliver Since engagement increases the pressure receivedby the fetal head during uterine contractions [11, 19), it may facilitate the production of type 1 dips. The present study was designed prospectively to allow the analysis of the etfects of amniotomy independently from the influence of the engagement of the fetal head. Further information which will be provided by this design, is the FHR pattern throughout labor with intact membranes. At present, this is not available since most obstetricians rupture the membranes artificially before cervical dilatation has :t:eached 6 cm. Furthermore, most of the FHR tracings are obtained during labor by means of the fetal scalp electrode which cannot be inserted when membranes are intact.