Contractions of the cervix in the latent phase of labour (original) (raw)
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Active contractions of the cervix in the latent phase of labour
1999
Objective To study the activity of the human uterine cervix at the onset of labour and further characterise cervical asynchronous electromyographic (EMG) activity in the latent phase. Design Prospective observational study. Setting Clinical ho spi tal in Ljubljana. Participants Forty-seven healthy nulliparous women with relatively unripe cervices requiring induction of labour. Methods Simultaneous registration of a cervical EMG and of the intrauterine pressure at the very early stage of labour; subsequent EMG signal processing to determine its time, amplitude and frequency parameters. Main outcome measures Simultaneous comparison of the cervical EMG and the mechanical activity of the uterine corpus to deduce electric al properties of the cervical smooth muscle tissue and its activity. Results EMG bursts, asynchronous with the contractions of the uterine corpus, were registered in 20 out of 47 women. In 14 women bursts appeared independent of uterine corpus contractions and in six th...
Electromyographic observations on the human cervix during labor
American journal of obstetrics and gynecology, 1987
The activity of smooth muscles in the cervix is one of the relevant factors for its dilatation during labor, but in humans it has not yet been sufficiently studied. Muscular activity may be observed by measuring electromyographic phenomena. In 60 parturient women of different parity and with various degrees of cervical ripeness at the onset of labor, the cervical electromyographic activity was measured through the entire course of labor in synchronization with uterine pressure measurements and also in 30 cases in synchronization with measurements of the uterine corpus electromyographic activity. The conditions necessary for successful measurements are described. The intensity of the cervical electromyographic activity was found to decrease with the level of cervical ripeness and with parity. When measured in the longitudinal direction, the cervical electromyographic activity resembled that of the uterine corpus, but when picked up from the circular lead, in a few cases of unripe cer...
Electromyographic activity in cervices with very low Bishop score during labor
International Journal of Gynecology & Obstetrics, 1995
Objectives: To investigate the activity of the smooth muscles in the cervix at the onset of induced labor and to further elucidate this activity in relation to uterine contractions and to the duration of the latent phase of labor, taking cervical ripeness into account. Methods: Cervical electromyographic (EMG) activity was studied at the onset of labor induced with amniotomy and oxytocin. Bipolar measurement of cervical electrical activity was performed. The root mean square of the cervical EMG activity and the intensity of intrauterine pressure in two groups of parturients with different cervical ripeness were compared. Results: The EMG activity was higher in the group with lower Bishop scores. We found a significant positive correlation between EMG activity and duration of the latent phase of labor. Conclusion; Smooth muscles in the human cervix are active during labor and act to some extent independently of the uterine corpus.
The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians, 2014
Objective: Limited data exist regarding uterine contraction intensity prior to membrane rupture. Using a novel technique of electrical uterine myography (EUM) we aimed to determine which factors affect myometrial activity during active phase of labor. Methods: EUM was prospectively measured in 37 women with singleton pregnancy at term during the active phase of labor until membranes' rupture. EUM was measured using non-invasive nine channels recorder with an EMG amplifier and three-dimensional position sensor. Uterine electrical activity was quantified with the EUM-index, defined as the mean electrical activity of the uterine muscle over a period of 10 min and measured in units of micro-Joule (microwatt per second [mW/s]). Results: The mean EUM-index at the first 10 min of the measurement was 3.3 ± 0.6 mW/s. In a stepwise linear regression model accounting potential confounders EUM was significantly affected by cervical dilatation (p = 0.005), maternal age (p = 0.04) and previou...
American Journal of Obstetrics and Gynecology, 1996
The primary aim of this study was to develop a noninvasive method for recording uterine contractile activity during pregnancy by systematically evaluating whether abdominal surface electromyography is representative of uterine electrical and contractile events. A secondary purpose was to use these techniques to determine when the uterus is in a state of preparedness for labor. Electrical activity was acquired by use of unipolar electrodes attached simultaneously to the uterine wall and to the abdominal surface of pregnant rats. Intrauterine pressure was recorded with a pressure transducer inserted in the uterine cavity. Computer-acquired records of electrical events (electromyography) and pressure were compared on different days of gestation, during spontaneous labor at term, or during preterm birth induced with an antiprogestin. Similarly, electrical activity was assessed after administration of agents that either stimulate (oxytocin) or inhibit (isoproterenol) contractility. Correlation analyses were performed between uterine electromyographic activity, surface electromyographic activity, and concomitant intrauterine pressure. The effects of vaginal wall stimulation were also evaluated at different times of pregnancy. The electrical activity recorded early in pregnancy (day 18) from the uterus consisted of irregular electrical bursts with little correspondence to the signals recorded from the surface (R2=0.006). Later in gestation (days 19 through 21) the electrical activity of the uterus became more regular, consisting of frequent bursts with accordance between the signals recovered from the uterus and those collected from the surface (R2=0.95). During labor (preterm or term) bursts recorded from either the uterus or the abdominal surface were of large amplitude and corresponded to ample changes in intrauterine pressure. Correlation coefficients between uterus and surface and uterus and pressure were R2=1 and 0.96, respectively. Similarly, during preterm labor the coefficients were R2=1 for uterine electromyographic activity versus surface electromyographic activity and R2=0.99 for uterine electromyographic activity versus intrauterine pressure. Vaginal stimulation in early gestation was not followed by subsequent signal conduction to the uterus, whereas during delivery activity induced in the vagina propagated to the uterus and consequently to the abdominal surface. Abdominal surface recording of uterine electrical events are representative of the activity generated by the muscle cells of the uterus. During term and preterm labor uterine electrical activity and intrauterine pressure achieve maximum activity. Electromyographic monitoring with vaginal stimulation of the uterus may allow prediction of when the uterus is in a state required for labor.
Uterine electrical activity and cervical shortening in the midtrimester of pregnancy
International Journal of Gynecology & Obstetrics, 2008
To determine whether a correlation exists between increased uterine electrical activity and cervical length (CL) in the midtrimester of pregnancy. In this case-control study, 312 asymptomatic nulliparous women underwent both uterine electromyographic assessment and ultrasound CL measurement between the 16th and 23rd weeks of a singleton pregnancy. The outcome measure was the difference in ultrasound CL measurement between the women found to have uterine action potentials on electromyography and those who did not. Action potentials were detected in 66 (21.1%) of the 312 women; and compared with the remainder of the study population, cervical length was significantly shorter in these women (35.7+/-8.9 mm vs 38.8+/-7.9 mm; P<0.01 by the Mann-Whitney test). Ultrasound CL measurement in the midtrimester was significantly shorter in women with increased uterine electrical activity.