Level Of Uterine Activity Research Articles

Effect of uterine contractions on fetal heart rate in pregnancy: a prospective observational study.

The new Holter monitoring technology enables long-term electrocardiographic recording of the fetal heart rate without discomfort for the mother. The aim of the study was to assess the feasibility of a fetal Holter monitor. This technology was further used to study fetal heart rate outside the hospital setting during normal daily activities and to test the hypothesis that uterine activity during pregnancy influences fetal heart rate. Prospective observational study including 12 healthy pregnant women at 20-40weeks of gestation. Data were collected using the Monica AN24 system. Outcome measures were fetal heart rate, maternal heart rate, and uterine activity categorized according to the strength of the electrohysterographic signal. The recordings had a median length of 18.8h, and fetal heart rate and maternal heart rate were obtained with success rates of 73.1 and 99.9%, respectively. Uterine activity was found to affect fetal heart rate in all participants. Compared with the basal tone and mild levels of uterine activity, moderate and strong levels of uterine activity were associated with increases in fetal heart rate of 4.0 and 5.7beats/min, respectively. At night, the corresponding increases were 4.9 and 7.6beats/min. Linear correlations were found between maternal heart rate and fetal heart rate in 11 of the 12 cases, with a mean coefficient beta of 0.189. Both maternal heart rate and fetal heart rate exhibitedadiurnal pattern, with lower heart rates being recorded at night. Uterine activity during pregnancy is associated with a graded response in fetal heart rate and may represent a physiological challenge for the development and adaptation of the fetal cardiovascular system.

Uterine activity, sperm transport, and the role of boar stimuli around insemination in sows

This paper describes changes in spontaneous myometrial activity around estrus, factors that affect myometrial activity, and the possible role of uterine contractions in the process of (artificial) insemination, sperm transport and fertilization. Myometrial activity in the sow increases during estrus. The activity is myogenic in origin, but several factors have been shown to affect myometrial activity. Natural mating stimulates uterine contractions through several mechanisms. The presence of a boar, rather than the act of mating, induces central oxytocin release in the sow and thus increases uterine activity. Estrogens in the ejaculate of a boar can trigger prostaglandin release by the endometrium and thus increase uterine activity. Tactile stimulation of the genital tract (cervix) or tactile stimulation of the back and flanks of the sow during artificial insemination does not cause a release of oxytocin. There is hardly any evidence for the effects of these latter stimuli on uterine activity, and if they are present at all, the effects are very small. Evidence for the effects of synthetic boar odor on oxytocin release and/or uterine activity is inconsistent. The mere presence of a boar during insemination, in contrast, clearly stimulates uterine activity through the release of oxytocin. Hormonal stimulation (intrauterine) of uterine activity with estrogens, prostaglandins, or oxytocins before, during or after insemination generally improves fertilization rate, especially in situations with reduced fertility. Therefore, uterine contractions are believed to play an important role in the transport of sperm cells to the oviducts after insemination. Whether uterine contractions are absolutely necessary for sperm transport through the uterine horns, however, is not clear. Intensive stimulation of uterine contractions using hormones can also reduce the fertilization rate, probably by increasing the reflux of sperm cells during insemination. In this respect, the presence of a boar during AI seems more adequate, as only sows with a low level of uterine activity show an increase in uterine activity in response to this stimulus.

Telemetric uterine contraction model in preterm cynomolgus monkeys

A telemetric-based model is presented for evaluation of uterine contractions and preterm labor (PTL) in pregnant cynomolgus monkeys. The model allows continuous monitoring of electromyography (EMG) and intrauterine pressure (IUP) as indicators of uterine activity. A pressure sensor was implanted into the amnion of pregnant monkeys on gestational day (GD) 120±3 and biopotential sensors were attached to the uterus. A telemetry transmitter was placed in a subcuticular pocket located in the flank. Venous catheters were tethered to the next room for dosing and blood sampling without disturbing the conscious animals. EMG and/or IUP were monitored continuously post-operatively. IUP is a reliable parameter for monitoring intrauterine activity, as demonstrated by a close relationship between bursts of activity in the EMG and increases in IUP. Animals close to term showed a basal level of uterine activity during the daytime, with irregular contractions of <10 mmHg. In the night, spontaneous contractions (10–40 mmHg; maximum between 18:00 and 01:00 h) appeared every 3–6 min. Artificial contractions of 15–40 mmHg that mimicked preterm labor were induced at any time of the day by infusion of 5–60 mU oxytocin (OT) per kilogram per hour. These contractions showed a dose-dependent response to OT, and were stable for up to 14 h of constant infusion of OT. Following withdrawal of oxytocin, contractions returned to baseline within 1 h. No desensitization of oxytocin-induced contractions was observed when oxytocin was administered daily for up to several weeks. This telemetric model characterizes uterine contractions in non-human primates and provides an excellent method to evaluate pharmacological characteristics of drug candidates intended to treat PTL.

Head-to-cervix force: an important physiological variable in labour. 2. Peak active force, peak active pressure and mode of delivery.

To assess the relation between peak active (above baseline) head-to-cervix force (paHCF) and peak active (above baseline) intrauterine pressure (paIUP) in labour, and to compare the relation between labours progressing well and ending in vaginal delivery and those labours progressing slowly and ending in caesarean section. Prospective observational study. The labour ward of a London teaching hospital. Forty women in labour who agreed to have an experimental head-to-cervix force probe and an intrauterine pressure catheter inserted. The relation was linear, with a correlation coefficient which ranged from 0.012 to 0.885 (mean value 0.438). The closeness of the relation did not correlate with the rate of cervical dilatation (r = 0.0192, P = 0.574) or the mode of delivery (r = 0.215, P = 0.183). However, in women who progressed well to a vaginal delivery, the mean slope of the paHCF to paIUP regression line was 0.72, significantly steeper than in women who progressed slowly and required delivery by caesarean section (mean slope = 0.45, t = 2.31, P = 0.02). Mean paIUPs were significantly higher in women progressing well and achieving a vaginal delivery than in those progressing slowly and requiring caesarean section (45.3 mmHg SD 7.5 vs 38.4 mmHg SD 11.4, t = 2.31, P = 0.02), but the overlap between the two groups was considerable. However, in keeping with their steeper paHCF/paIUP slope, women progressing well to a vaginal delivery had substantially higher head-to-cervix forces (46.4 gWt SD 11.8 vs 28.3 gWt SD 8.2, t = 5.22, P < 0.00001) than those progressing slowly and requiring caesarean section, and there was much less overlap between paHCF than paIUP. This resulted in paHCF being a much better discriminating variable than paIUP for mode of delivery. The relation between paHCF and paIUP is linear, but there is a wide variation in the degree of correlation between one woman and another. Women with a steep slope of paHCF relative to paIUP are more likely to achieve a high mean paHCF, progress rapidly in labour and achieve a vaginal delivery than women with a flap slope, although mean paIUPs do not differ substantially between the two groups. The level of paHCF was substantially better than cervical dilatation rate at predicting mode of delivery. These results suggest that head-to-cervix force is sensitive to factors determining mode of delivery which are not reflected in either the level of uterine activity as measured by intrauterine pressure, or cervical compliance as measured by cervical dilatation rates.

Uterine activity in spontaneous labour and maternal peripheral plasma prostaglandin E 2 and F 2alpha metabolites

The relationship between maternal peripheral plasma concentrations of prostaglandin E2 and prostaglandin F2 alpha metabolites (bicyclo-PGEM and PGFM respectively) and the level of uterine activity in spontaneous labour was studied in 10 nulliparous and 10 multiparous women. Plasma prostaglandin metabolites were measured by radioimmunoassay. Uterine activity was quantified by computer analysis of changes in intrauterine pressure and expressed as mean active pressure (MAP). As labour progressed, both parity groups showed a significant rise in MAP which was associated with a significant increase in the levels of PGFM. However, the percentage rise in PGFM did not significantly correlate with the percentage rise in MAP. At all stages in labour PGFM and MAP levels were higher in the nulliparous group compared with the multiparous group. Bicyclo-PGEM levels showed no significant change in the nulliparous group but rose in late first stage/second stage in the multiparous group. Our observations support a role for prostaglandin F2 alpha in the generation of uterine activity in spontaneous labour. However, further study is required to elucidate the mechanisms controlling prostaglandin production by the fetal membranes and decidua in vivo, and how this relates to maternal peripheral plasma prostaglandin metabolite concentrations and the level of uterine activity.

Characteristics of Uterine Activity During Labor After Previous Cesarean Section

ABSTRACT Uterine activity was studied during labor in 36 women who had previous cesarean sections. There was no difference in uterine activity between those delivered vaginally (66%) or those who n...

Normal levels of uterine activity in primigravidae and women of high parity in spontaneous labour

SummaryUterine activity was measured in 30 primigravidae and 30 women of parity 5 or more. All were in the active phase of the first stage of spontaneous labour and were delivered spontaneously vaginally—without augmentation with oxytocin. The cumulative uterine activity integral values and the values at individual cervical dilatations were significantly lower with parity 5 or more than in primigravidae. The overall values (mean ± s.d.) of the integral were 1574 ± 468 KPa/15 min and 1139 ± 442KPa/15 min for primigravidae and high parity women respectively. A gradual rise in uterine activity as labour advanced from 3–10 cm cervical dilatation was observed.

7 Assessment and management of uterine contractions

The last decade has seen a marked rise in Caesarean section (CS) rates and a steady decline in perinatal mortality rates (PNMR), with limited evidence to suggest a causal relationship (O'Driscoll and Folley, 1983; Shearer, 1983). More recently, there has been a smaller decline in perinatal mortality rates, despite the continuing trend of rising CS rates both in the developed (Maternity Alliance, 1983; National Institute of Health (NIH) consensus statement, 1981) and developing countries (Arulkumaran et al, 1985a). Such a trend has been attributed to the obstetrician's concern to reduce perinatal morbidity, but parents' attitudes to a small family size, privatization of health care, and concern over litigation, have also contributed to increasing numbers of Caesarean births. The NIH consensus report from the USA and recent reports from the UK (Yudkin and Redman, 1986), have highlighted dystocia and previous CS as major contributory factors, fetal distress and breech presentation playing a more minor role in this increasing trend. The uterus, whilst contracting to effect delivery of the fetus, reduces the utero-placental blood supply intermittently resulting, at times, in fetal hypoxia necessitating an abdominal delivery. This complication is more likely when oxytocin is used injudiciously to augment weak uterine contractions. Hyperstimulation of the uterus, and its consequences, has become the commonest cause of litigation in obstetric practice in the USA (Fuchs, 1985). Owing to concern over this, or due to lack of understanding of augmentation of labour, oxytocin is not used, or is misused, in the management of abnormal labour, resulting in prolonged labour and probable CS for dystocia. These patients are subjected to repeat CS in their next pregnancy, thus increasing the CS rate further. Despite adequate evidence of uncomplicated vaginal deliveries in cases with previous CS, many centres practise routine repeat CS. Some permit labour in cases with previous lower segment CS if in spontaneous labour with normal progress, but are reluctant to augment abnormal labour. These attitudes are related to the difficulty in predicting and diagnosing scar dehiscence. In such situations, assessing levels of uterine activity and limiting excessive activity may be of value. The three management of problems of dystocia, fetal distress and previous CS are related to uterine contractions. A

Uterine contraction pressures with oxytocin induction/augmentation.

Uterine contraction pressures were quantified (in Montetevideo units) in 109 women at term gestation who received oxytocin for induction or augmentation of labor and whose labor resulted in a spontaneous vaginal delivery. Newborn five-minute Apgar scores were greater than or equal to 8 in 108 of the 109 neonates, and no immediate neonatal morbidity was attributable to the oxytocin stimulation of labor. Women undergoing oxytocin induction had significantly greater uterine contraction pressures than those with oxytocin augmentation. During oxytocin induction 91% of women achieved at least 200 to 224 Montevideo Units and 40% at least 300 Montevideo units versus 77 and 7.7%, respectively, during augmentation of labor. With concurrent fetal monitoring these levels of uterine activity should be sought before consideration of a cesarean delivery because of presumed cephalopelvic disproportion or failure to progress.

The Effect of Oxytocin Infusion on Uterine Activity Levels in Slow Labour

Uterine activity was studied in 31 women who were progressing slowly in spontaneous labour. In 75%, levels of uterine activity were below the tenth centile for normal spontaneous labour (mean uterine activity integral, UAI, 593 kPas/15 min; SD 296). Following oxytocin infusion, there was a significant increase in uterine activity to a mean of 1124 kPas/15 min (SD 276), which was the same as in normal spontaneous labour. The response to oxytocin was dependent upon the pre-existing level of uterine activity, and sensitivity to oxytocin, rather than the dose rate; 84% responded to infusion rates of less than 8 mU/min. The response to oxytocin was best expressed in terms of active contraction area (uterine activity integral, UAI) or Montevideo units, rather than the frequency or active pressure of contractions. The rate of cervical dilatation following oxytocin augmentation could not be predicted either by the increase in uterine activity or by the actual level of activity achieved.

The effect of oxytocin infusion on uterine activity levels in slow labour.

Uterine activity was studied in 31 women who were progressing slowly in spontaneous labour. In 75%, levels of uterine activity were below the tenth centile for normal spontaneous labour (mean uterine activity integral, UAI, 593 kPas/15 min; SD 296). Following oxytocin infusion, there was a significant increase in uterine activity to a mean of 1124 kPas/15 min (SD 276), which was the same as in normal spontaneous labour. The response to oxytocin was dependent upon the pre-existing level of uterine activity, and sensitivity to oxytocin, rather than the dose rate; 84% responded to infusion rates of less than 8 mU/min. The response to oxytocin was best expressed in terms of active contraction area (uterine activity integral, UAI) or Montevideo units, rather than the frequency or active pressure of contractions. The rate of cervical dilatation following oxytocin augmentation could not be predicted either by the increase in uterine activity or by the actual level of activity achieved.

Intrauterine-pressure studies in African nulliparae: delay, delivery and disproportion.

Uterine activity was measured in 43 African nulliparae who were in the active phase of spontaneous labour and in whom delay in cervical dilatation had occurred. Details of labour were recorded on a partogramme, on which an alert and an action line had been drawn, and which were 2 h apart. Delay was defined as a cervical dilatation rate of less than 1 cm/h. Uterine activity was measured with a fluid-filled intrauterine catheter, an external strain gauge and a pressure-curve integrator. The uterine activity levels which were observed in association with delay are considerably less than those associated with normal labour progress. The uterine activity levels that were associated with pitocin augmentation after the action line and which resulted in vaginal delivery have been analysed. They were similar to the levels observed in normal labour. The uterine activity levels which were associated with 'failure to progress in labour' beyond the action line have also been analysed. It is argued that a minimum uterine activity level of 1800 kPas/15 min is required to fully test the cephalopelvic relation.

Termination of midtrimester pregnancy by serial intramuscular injections of 15(S)-15-methyl-prostaglandin F2α

Midtrimester abortion was successfully induced in 117 of 120 patients with serial intramuscular injections of 15(S)-15-methyl-prostaglandin F2alpha (15-me-PGF2alpha). The mean abortion time was 14.12 hours, and parous patients aborted in a mean of 12.85 hours-significantly faster than nulliparous patients who aborted in a mean of 15.24 hours. Ninety-four per cent of the 117 successfully induced abortions occurred in less than 24 hours and 46 per cent in less than 12 hours. Uterine activity was monitored and analyzed in nine patients. Uterine response to a single intramuscular injection of 100 mug of 15-me-PGF2alpha was characterized by the appearance of low-amplitude, high frequency contractions and a rapid increase in baseline intrauterine tonus. A high level of uterine activity, 900 Montevideo Units, was observed within 30 minutes of the first intramuscular injection of 15-me-PGF2alpha. This activity was not maintained and decreased by approximately 30 per cent at the time of the second injection at 1 hour. It was not until 6 hours of 15-me-PGF2alpha therapy that activity stabilized at approximately 500 Montevideo Units. Even though all patients were premedicated with antiemetic and antidiarrhea agents, 68 of 120 patients experienced gastrointestinal side effects related to the 15-me-PGF2alpha administration. Vomiting was the most prevalent side effect, occuring in 65 patients, but the episodes were not severe, were well tolerated by the patients and did not necessitate the termination of prostaglandin administration in any of the patients. In this study abortion was successfully induced between weeks 9 to 27 of gestation. It was observed that patients with gestations of 16 weeks or less aborted significantly faster than patients with gestations of 17 weeks or more, which indicates that this method is highly effective in the induction of abortion within the "gray zone", 12 to 16 weeks of gestation.

Intra-amniotic prostaglandin administration — A challenge to the currently used methods for induction of midtrimester abortion

The present investigation was undertaken to evaluate the degree of uterine stimulation and abortifacient efficacy of a single intra-amniotic injection of prostaglandin. A high dose of PGF 2a was compared with different dose levels of 15(s)-15-methyl-PGF 2a. 1. 1. Forty mg PGF 2a induced an initially high level of uterine activity followed by a gradual decline. Inefficient contractility, resulting from a transient response, was occasionally observed. The clinical trials resulted in a success rate of 76% and were associated with a comparatively high incidence of side-effects. 2. 2. Intra-amniotic administration of 15-me-PGF 2ainduced a different type of response characterized by a gradual initiation of uterine stimulation but a sustained effect. One mg of the analogue proved to be too low as a single abortifacient dose whereas 2.5 and 5.0 mg induced abortion in nearly 100% of the cases. The intermediate dose (2.5 mg) resulted in a high level of uterine contractility, a high success rate and a low incidence of side-effects. These results were compared with available data on hypertonic saline abortions. The use of 15-me-PGF 2a seems to offer certain advantages of practical significance.

The response of the midpregnant human uterus to vaginal administration of prostaglandin suppositories

The effect of a new form of vaginal prostaglandin suppositories on the contractility of the midpregnant uterus was studied in 20 volunteers admitted to the hospital for induction of legal abortion. Ten patients were given 50 mg PGF 2α and 10 other patients 20 mg PGE 2. The uterine contractions were recorded continuously for a period of 10 hours following the insertion of a single vaginal suppository. Fifty mg PGF 2α induced a maximum uterine activity during the third hour followed by a rapid decline to reach a level close to zero by the 10th hour. Twenty mg PGE 2 stimulated the uterus to achieve a maximum activity at the 5th hour. This high level of activity was sustained throughout the rest of the observation period. The incidence of vomiting and diarrhoea showed a reasonable correlation to the level of uterine activity induced within the two groups. The potency of vaginal administration of 20 mg PGE 2 was also reflected by the fact that 7 out of the 10 cases in this group aborted within 10 hours following a single suppository as compared to only one out of 10 in the 50 mg PGF 2α group. These results indicate that vaginal administration of 20 mg PGE 2 is far more potent than 50 mg PGF 2α. The possible role of the new prostaglandin suppositories for future clinical trials is discussed.

The effect of prostaglandins on the human pregnant uterus.

Observations were made in 15 patients in late pregnancy (36-42 weeks) and in 5 in early pregnancy in order to study the effects of intravenous infusion of pure prostaglandins on the mobility of the human pregnant uterus. Uterine contractibility was recorded by means of the Oxford Tocograph. Using both the E prostaglandins and those of the F series, stimulation of myometrial contractility was observed. The oxytocic properties of the E prostaglandins were particularly marked and reliable. In late pregnancy, and at term, the response was characterized by an increase in both the frequency and amplitude of contractions, without -- in the dosage used -- any appreciable increase in tone. Hypertonus was a feature of the response during the early months of pregnancy. Slow in action, the induced level of uterine activity tended to persist or recur for long after the infusion was discontinued and, particularly in the case of prostaglandin E2, was often followed by the successful induction of labor. On the basis of this study, it appears that the effect of prostaglandins in bringing about termination of pregnancy may be indirect.