[Views on the mechanisms of labor onset].
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Female↗
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Prostaglandin e and f receptor expression and myometrial sensitivity at labor onset in the sheep.
Prostaglandins (PGs) play a pivotal role in the initiation and progression of term and preterm labor. Uterine activity is stimulated primarily by PGE(2) and PGF(2alpha) acting on prostaglandin E (EP) and prostaglandin F (FP) receptors, respectively. Activation of FP receptors strongly stimulates the myometrium, whereas stimulation of EP receptors may lead to contraction or relaxation, depending on the EP subtype (EP1-4) expression. Thus, the relative expression of FP and EP1-4 may determine the responsiveness to PGE(2) and PGF(2alpha). The aims of this study were to characterize the expression of EP1-4 and FP in intrauterine tissues and placentome, together with myometrial responsiveness to PG, following the onset of dexamethasone-induced preterm and spontaneous term labor. Receptor mRNA expression was measured using quantitative real-time polymerase chain reaction using species-specific primers. There was no increase in myometrial contractile receptor expression at labor onset, nor was there a change in sensitivity to PGE(2) and PGF(2alpha). This suggests expression of these receptors reaches maximal levels by late gestation in sheep. Placental tissue showed a marked increase in EP2 and EP3 receptor expression, the functions of which are unknown at this time. Consistent with previous reports, these results suggest that PG synthesis is the main factor in the regulation of uterine contractility at labor. This is the first study to simultaneously report PG E and F receptor expression in the key gestational tissues of the sheep using species-specific primers at induced-preterm and spontaneous labor onset.
Animals↗
[Correlation of labor onset, membrane rupture and birth with meteorological events].
UNLABELLED: The birth-physiological events: beginning of labour, rupture of membranes and delivery of 6 539 cases in the years 1976 to 1981 can be correlated with five groups of weather situations: no definite pressure gradient, anticyclonic, meridional, zonal mild maritime, and cyclonic. THE RESULTS: temporary increase of the frequency of births in weather with no definite pressure gradient in summer, in anticyclonic weather in winter and in cyclonic weather in the first half of the year, correspond only partly (namely for the changes within the group of cyclonic weather) with the temporarily increasing number of births during a weather front, as it ist known from experience. The causes of the correlations found out are unknown, and the setting up of a statistical model and consequently an obstestrical-metereological forecast is impossible for the time being.
Austria↗
[Control of labor onset in the human].
While the mechanism of the initiation of labor in humans has not been clarified satisfactorily, it is of major clinical interest, particularly with a view to understanding and avoiding preterm labor. Progesterone, whose role can now be determined in greater detail by the use of newly developed progesterone antagonists, and estrogens both play a role. Recently, attention has focused not only on contraction-stimulating substances such as oxytocin and prostaglandins, but also on cytokines, which have been implicated in the pathogenesis of preterm labor related to intrauterine infection. A model describing the various steps leading to regular uterine contractions is discussed and the resulting implications on stimulation and inhibition by pharmacological substances are outlined.
Animals↗
Influence of gestational age on the time from spontaneous rupture of the chorioamniotic membranes to the onset of labor.
Our goal was to assess the influence of gestational age on the timing of labor onset following spontaneous rupture of the chorioamniotic membranes. The 24,831 patients in the Nova Scotia Atlee perinatal database from 1986 to 1992 whose membranes ruptured prior to labor onset and had live births were analyzed using life-table analysis methods. The probability of labor onset at specified intervals following rupture was markedly lower when rupture occurred earlier in gestation. Pregnancies of < 33 weeks' gestation were less than half as likely as term pregnancies to proceed to labor within 24 hours and pregnancies of 33-36 weeks' gestation were 50-75% as likely as term pregnancies to progress within that period. These data provide clear evidence that the earlier in gestation the rupture occurs, the less likely labor onset is within specified time periods. This pattern supports the contention that preterm rupture of membranes is etiologically distinct from preterm labor.
Amnion↗
[Prostaglandins and labor onset].
Prostaglandins and lipoxygenase metabolites of arachidonic acid (Eicosanoids) are crucial paracrine regulators of labor. There are many informations about in vitro production and the physiological or pathophysiological role and clinical importance of these substances. However, the all decisive mechanism of the involvement of eicosanoids in birth process is still unknown. In this review we describe the present knowledge about endocrine, paracrine and autocrine regulations of uterine contractions.
Animals↗
[Role of the cervix uteri at labor onset from ultrasound studies].
The cervix uteri is of greatest importance for the environment of the fetus. The sonographic imaging of the cervix uteri can be done by transabdominal, perineal and transvaginal route. Each of these methods are associated with specific advantages and disadvantages. During the time of gestation the cervix uteri can be measured sonographically concerning the length, the thickness, the width of the cervical canal and in addition the diameter of the internal and the external os. At the beginning of labour the cervix shows a transformation: a shortening with an increase of thickness. The phase of contraction is followed by a phase of reformation. Individual formations of the cervix regarding the a premature opening of the internal os or the external os could be demonstrable without clinical symptoms. By W. Eppel a score-like formula "Incompetence-Factor" was described for a quantification of these measurements.
Cervix Uteri↗
[Uterine contraction and labor onset. Overview].
A survey is given about the general theories of beginning of labour. In this topic the influence of excitation of the uterus muscle is explained together with the importance of hormonal induction.
Animals↗
[Prolonged pregnancy--prostaglandins as the cause of labor onset].
The causes of prolonged pregnancy are still largely unknown and their investigation requires a detailed observation of potential birth-initiating stimuli on the endocrine and biomolecular level. A large number of clinical and biochemical studies point to the central importance of prostaglandins for the beginning of human birth. The main places of origin of the intensified prostaglandin formation and release are the amnion and the decidua which has "macrophage-like" properties and functions. The superordinate regulation and trigger mechanisms for intensified uterine prostaglandin production has not been sufficiently investigated either. Possible factors currently being debated include local changes in estrogen and progesterone biosynthesis in fetal membranes and decidua, subclinical inflammatory reactions with the activation of macrophages and the consecutive release of cytokines, and a loss of maternal immune tolerance with a time-determined rejection reaction. In addition, the substances inhibiting and stimulating prostaglandin synthesis have been detected in the amniotic fluid, fetal membranes and decidua. The fetus itself also plays an important part in the initiation of labor. Prolongation may be due to anatomic functional disturbances of the one hand which prevent the activation of the fetal hypothalamic-hypophyseal-adrenal axis and the release of the birth-initiating stimuli originating in the fetus; on the other hand, an elevated immune tolerance with a delayed rejection reaction or the lack of "bacterial stimulus" may inhibit the activation of the macrophages and hence the formation of cytokines. The consequences would be the development and release of a quantity of prostaglandins from the fetal membranes and decidua insufficient to overcome the pregnancy-maintaining safety systems.(ABSTRACT TRUNCATED AT 250 WORDS)
Amnion↗
[Secretion of inflammatory cytokines and prostaglandins by fetal trophoblast cells induces uterine contraction and labor onset].
OBJECTIVE: Induce infection-associated cytokines intrauterine secretion of prostaglandins and term labor? METHODS: Concentrations of Il-6, Il-1 beta, TNF-alpha, PGF2 and PGF2 alpha were determined in cervical secretions and amniotic fluid during spontaneous term labor. The supernatant of amnion-, chorion-, decidua- and trophoblast cells, cultured after elective cesarean section or spontaneous delivery, was analysed for cytokine- and prostaglandin activity. RESULTS: Term labor always is associated with intrauterine cytokine- and prostaglandin release. Increased production of cytokines and prostaglandins in case of normal term labor only was found by fetal trophoblast cells. CONCLUSIONS: Signal for parturition is of trophoblast and therefore of fetal origin.
Amniotic Fluid↗
[Induced labor vs. spontaneous labor onset. Aspects from the viewpoint of the midwife].
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Attitude of Health Personnel↗
[Detection of fetal distress before labor onset with an atropine test].
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Atropine↗
Maternal morbidity associated with cesarean delivery without labor compared with spontaneous onset of labor at term.
OBJECTIVE: To estimate the maternal morbidity associated with cesarean deliveries performed at term without labor compared with morbidity associated with spontaneous labor. METHODS: A 14-year, population-based, cohort study (1988-2001) using the Nova Scotia Atlee Perinatal Database compared maternal outcomes in nulliparous women at term undergoing spontaneous labor for planned vaginal delivery with singleton, cephalic presentation and nulliparous women delivering by cesarean without labor. RESULTS: From a total of 18,435 pregnancies, which satisfied inclusion and exclusion criteria, 721 were cesarean deliveries without labor. There were no maternal deaths or transfers for intensive care. There was no difference in wound infection, blood transfusion, or intraoperative trauma. Women undergoing cesarean deliveries without labor were more likely to have puerperal febrile morbidity (relative risk [RR] 2.2; 95% confidence interval [CI] 1.1, 4.5; P=.03), but were less likely to have early postpartum hemorrhage (RR 0.6; 95% CI 0.4, 0.9; P=.01) compared with women entering spontaneous labor. Subgroup analyses of maternal outcomes in women delivering by spontaneous and assisted vaginal delivery and cesarean delivery in labor were also performed. The highest morbidity was found in the assisted vaginal delivery and cesarean delivery in labor groups. CONCLUSION: The increased maternal morbidity in elective cesarean delivery compared with spontaneous onset of labor is limited to puerperal febrile morbidity. Maternal morbidity is increased after assisted vaginal delivery and cesarean delivery in labor compared with cesarean delivery without labor.
Adult↗
Does the onset of spontaneous labor at term influence fetal biophysical test parameters?
Recent data suggest that fetal breathing movement incidence declines while fetal heart rate (FHR) and body movement incidence do not change within 72 hours of spontaneous term labor. We conducted a retrospective study to determine whether the length of time from testing to spontaneous labor onset could influence these biophysical test parameters. Eighty-one normal term fetuses underwent 60-minute tests 1-40 days before the onset of spontaneous labor: 41 were tested within 7 days of labor (19 within 3 days and 22 within 4-7 days) and 40 were tested more than 7 days before labor. We simultaneously acquired and analyzed FHR baseline, frequency of accelerations between ten to 14 beats per minute and more than 15 beats per minute in amplitude, percent of time spent in breathing and moving, and fetal breath rate. These biophysical parameters were not significantly different between the groups, implying that they may continue to provide clinically useful information in the prelabor period.
Female↗
Influence of labor induction on obstetric outcomes in patients with prolonged pregnancy: a comparison between elective labor induction and spontaneous onset of labor beyond term.
BACKGROUND: Prolonged pregnancy is the most frequent reason for induction of labor. This study aims to determine the effects of labor induction on delivery outcome and to quantify the risks of cesarean delivery associated with labor induction in post-date pregnancies. PATIENTS AND METHODS: This retrospective case-control study included a total of 205 women who reached 42 weeks' gestation (41 weeks and 3 days) between January 2002 and April 2004 and who were scheduled for induction of labor with vaginal prostaglandins. These cases were matched for age and parity with controls in spontaneous labor beyond 41 weeks' gestation. Women with any additional medical or obstetric risk factors were excluded from the study. Maternal, neonatal and delivery outcomes were the main variables of interest. RESULTS: During the study period the data of 410 women were available for analysis. Our data revealed that the use of amniotomy (p=0.02), oxytocin (p=0.006) and epidural analgesia (p=0.001) was increased significantly in the induction group compared with the control group of women with spontaneous onset of labor beyond term. The frequency of cesarean delivery and vacuum extraction was also significantly higher in the induction group (p=0.0001). The Bishop score before induction was an important factor that affected the delivery outcome, resulting in significantly higher rates of cesarean section and vacuum extraction when the score was unfavorable (p=0.0001). A univariate regression model revealed induction per se (p=0.0001), primiparity (p= 0.0001), increased maternal age (p=0.006) and an unfavorable Bishop score (p=0.0001) as statistically significant risk factors for cesarean section. In a multivariate logistic regression model, primiparity (p=0.03), increased maternal age (p=0.02) and an unfavorable Bishop score (p=0.01) remained independent risk factors for cesarean section. High infant birth weight was also an independent risk factor (p=0.03). CONCLUSIONS: Our data suggest that women undergoing labor induction because of prolonged pregnancy should be sufficiently informed regarding the risks of a cesarean section or a vacuum extraction. Furthermore, the option of elective cesarean section should be considered, particularly in primiparous women with an unfavorable cervix, higher age, and high estimated infant birth weight.
Adolescent↗
Women's recognition of the spontaneous onset of labor.
BACKGROUND: Despite extensive research on the onset of labor, almost no data are available on women's perception of labor onset. We undertook a study to assess how women experience spontaneous onset of term labor. METHODS: A semistructured questionnaire was given to 235 women admitted in spontaneous labor at term. Women noted when labor had started, whether and when membranes had ruptured, and answered an open question about how labor had announced itself. Two investigators independently subdivided women's experiences on how labor had started into 369 sampling units corresponding to 8 predefined categories. RESULTS: Nearly two-thirds of the sampling units (63.4%) related to recurrent and nonrecurrent pain, and the ratio between the two types was higher for multiparas than for nulliparas. The number of women and sampling units were identical for each of the following categories: watery fluid (n = 47), blood-stained loss (n = 33), gastrointestinal symptoms (n = 10) and altered sleep patterns (n = 11); 22 sampling units relating to emotional upheaval were mentioned by 16 women. Although 33.6 percent of women experienced rupture of membranes before admission, only 21.6 percent associated it with their onset of labor, either alone (11.5%) or in association with other categories (10.1%). CONCLUSIONS: Although women experience onset of labor in a variety of ways, for most it is a concrete event. Studies on duration of labor should take women's perception of onset of labor as a starting point rather than rely on surrogate measures.
Adolescent↗
An evaluation of the pelvic score by the quantification theory for categorical data.
The scoring system for pelvic examination used in Tsukuba University Hospital was evaluated by the quantification theory to investigate the precision in predicting the date of labor onset. The objects of this study were 137 nulliparous gravidae and 142 multiparous gravidae who had spontaneous onset of labor at full-term. In this analysis, we used 15 categories of findings in the examination as independent variables, and as the objective variable we used the interval from the examination to the labor onset. The multiple correlation coefficients in nulliparae was 0.593 and in multiparae 0.598. The following conclusions were reached concerning the assessment of labor onset: (1) The consistency of the cervix and the engagement of the vertex in nulliparous gravidae should be given more consideration. (2) In multiparous gravidae the dilatation of the cervix and the engagement of the vertex are important factors. (3) A different scoring system should be employed for both nulliparae and multiparae.
Evaluation Studies as Topic↗