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PubMed1983

[Importance of oxytocin sensitivity for the spontaneous onset of human labor].

The significance of oxytocin for the onset of labour in humans is disputed, mainly because there is no increase in oxytocin concentration in the peripheral maternal blood before onset of labour. However, Fuchs et al. have recently shown that the concentration of oxytocin receptors in the myometrium is significantly higher directly before onset of labour than at the onset of spontaneous contractions. To establish a correlation with the clinical sensitivity to oxytocin, the authors determined the oxytocin sensitivity by means of intravenous administration of 3 X 10 m I.U. of oxytocin with continuous tocographic recording. Parallel to this determination, the cervical score was measured according to Bishop. The patients were 26 healthy pregnant women in whom both parameters were determined daily until onset of spontaneous labour pains. The sensitivity to oxytocin increased significantly during the last few days before spontaneous onset of labour. On the day before onset of pains, almost all of the pregnant women showed maximum sensitivity to oxytocin. Parallel to this, the cervical, scores also increased; on the day before onset of labour pains, almost all pregnant women had a cervical score of 5 or more than 5. On the basis of these results, which concur accurately with the results of measurement of oxytocin receptor concentrations, it is definitely possible to refute the arguments that oxytocin is irrelevant for the onset of labour because its concentration in the maternal plasma does not increase before the pains begin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Increasing quantity of maternal immunoglobulin G in trophoblastic tissue before the onset of normal labor.

While levels of maternal immunoglobulin G (IgG) increase in the fetal circulation during the third trimester, actual trophoblastic concentrations have not been extensively studied. To investigate this process, placentas from 71 patients with gestational ages between 26 and 42 weeks were examined by means of a peroxidase-antiperoxidase immunostaining technique specific for IgG. Linear regression revealed a significant increase in antibody with advancing gestational age (r = 0.36, p less than 0.01). In addition, placentas from patients in spontaneous term labor revealed a significantly higher antibody level when compared with those of patients at term delivered electively before the onset of labor (mean +/- SEM 2.6 +/- 0.2 vs 1.7 +/- 0.3, p less than 0.02). Patients in premature labor failed to demonstrate this increase in antibody staining. One possible explanation for these findings is an enhanced recognition of the fetal trophoblastic tissue by the maternal immune system at term. It also suggests immunologic factors may play an important role in the initiation of normal labor.

Female↗

PubMedDate not supplied

Resolving the uncertainty of preterm symptoms: women's experiences with the onset of preterm labor.

OBJECTIVE: To describe expectant women's experiences with the onset of preterm labor. DESIGN: Qualitative, using grounded theory methods. SETTING: Southwestern tertiary women's hospital. PARTICIPANTS: Thirty pregnant women who were less than 35 weeks gestation, had experienced preterm labor within the past 7 days, and had no previous experience with preterm labor. DATA SOURCE: Taped and transcribed interviews. RESULTS: Themes that emerged from the interview data included the following: recognition and naming of sensations, a consistent pattern of attribution of symptoms, the threat or risk inferred by the attributed cause of the symptom pattern, the associated certainty or uncertainty about these attributions, the process of interpreting and verifying symptom meaning, and the decision to self-manage the symptoms or engage health care assistance. The core process of women experiencing the onset of preterm labor symptoms was identified as "resolving the uncertainty of preterm labor symptoms: recognizing and responding to the possibilities." CONCLUSIONS: Preterm labor often is not within expectant women's consciousness. They may attribute the symptoms to nonthreatening causes, which results in delays in seeking care for preterm labor. Education about symptom patterns at the onset of preterm labor will increase the probability that women and their health care providers will recognize and interpret the early, subtle symptoms that herald the onset of preterm labor. Uncertainty in illness theory and attribution theory offer frameworks for understanding women's experiences with the onset of preterm labor.

Adult↗

PubMed2006

Preterm labor is induced by intraamniotic infusions of interleukin-1beta and tumor necrosis factor-alpha but not by interleukin-6 or interleukin-8 in a nonhuman primate model.

OBJECTIVES: The purpose of this study was to determine the relative contributions of individual proinflammatory cytokines and chemokines to the triggering of preterm labor. STUDY DESIGN: Eighteen chronically instrumented pregnant rhesus monkeys at 135 +/- 3 days gestation (term = 167 days) received 1 of 5 intraamniotic infusions: (1) interleukin-1beta (IL-1beta) (10 microg; n = 5), (2) tumor necrosis factor-alpha (TNF-alpha) (10-100 microg; n = 5), (3) IL-6 (20 microg twice a day; n = 2), (4) IL-8 (20 microg twice a day; n = 2), and (5) saline control (n = 4). Primary study outcomes were the mean uterine hourly contraction area (mm Hg x s/h) in 24 hours during peak response to cytokine infusion (all groups) and the interval from cytokine infusion until labor onset (IL-1beta, IL-6, and IL-8 groups). Secondary outcomes were quantities of amniotic fluid cytokines and chemokines (IL-1beta, TNF-alpha, IL-6, and IL-8), prostaglandins E2 and F2alpha, leukocytes, and matrix metalloproteinase-9 (MMP-9). Histopathology of fetal lungs and placental membranes was assessed. RESULTS: IL-1beta stimulated the most intense contraction patterns, resulting in preterm labor in all cases. TNF-alpha induced a variable degree of uterine activity among individual animals stimulating either preterm labor (n = 2) or a uterine contraction pattern of moderate intensity (n = 3). Despite prolonged elevations in amniotic fluid levels, neither IL-6 nor IL-8 induced preterm labor or an increase in uterine activity until near term. The mean interval from the initiation of IL-6 and IL-8 infusion to the onset of labor was significantly longer than after IL-1beta (21.9 vs 1.1 days; P < .01), and did not differ from the saline control group (27.6 days; P = NS). Intraamniotic infusion of IL-1beta or TNF-alpha was associated with significant elevations in all tested amniotic fluid cytokines, IL-8, prostaglandins, MMP-9 and leukocytes compared with gestational age-matched saline controls. IL-6 and IL-8 infusions were not associated with increases in IL-1beta or TNF-alpha and only produced a moderate increase in amniotic fluid prostaglandins. All cytokine infusions induced histologic chorioamnionitis and an accumulation of neutrophils in fetal lungs. CONCLUSION: Preterm labor was induced by intraamniotic infusions of IL-1beta and TNF-alpha, but not by IL-6 or IL-8 although inflammatory changes in fetal membranes and lungs were uniformly present. Our results indicate a primary role for IL-1beta and TNF-alpha in the triggering of preterm labor associated with inflammation or infection.

Amniotic Fluid↗

PubMed2006

Effect of coitus at term on length of gestation, induction of labor, and mode of delivery.

OBJECTIVE: To determine coital incidence at term and to estimate its effect on labor onset and mode of delivery. METHODS: Healthy women with uncomplicated pregnancies and established gestational age were recruited to keep a diary of coital activity from 36 weeks of gestation until birth and to answer a short questionnaire. Two hundred women with complete coital diaries were available for analysis. Outcome measures include coitus, postdate pregnancy (defined as pregnancy beyond the estimated date of confinement), gestational length of at least 41 weeks, labor induction at 41 weeks of gestation, and mode of delivery RESULTS: Reported sexual intercourse at term was influenced by a woman's perception of coital safety, her ethnicity, and her partner's age. After multivariable logistic regression analysis controlling for the women's ethnicity, education, occupation, perception of coital safety, and partner's age, coitus at term remained independently associated with reductions in postdate pregnancy (adjusted odds ratio [AOR] 0.28, 95% confidence interval [CI] 0.13-0.58, P = .001), gestational length of at least 41 weeks (AOR 0.10, 95% CI 0.04-0.28, P < .001), and requirement for labor induction at 41 weeks of gestation (AOR 0.08, 95% CI 0.03-0.26, P < .001). At 39 weeks of gestation, 5 (95% CI 3.3-10.3) couples needed to have intercourse to avoid one woman having to undergo labor induction at 41 weeks of gestation. Coitus at term had no significant effect on operative delivery (adjusted P = .15). CONCLUSION: Reported sexual intercourse at term was associated with earlier onset of labor and reduced requirement for labor induction at 41 weeks. LEVEL OF EVIDENCE: II-2.

Adult↗

PubMed1993

The dynamics of prostaglandin metabolism in human fetal membranes and decidua around the time of parturition.

To address whether prostaglandins (PGs) produced in the amnion can gain access to the myometrium, we used three in vitro systems to determine the characteristics of PG secretion, metabolism, and transfer in amnion, chorion, and decidua around the time of parturition. PG metabolism, measured in explant cultures or cytosol preparations, occurs predominantly by the enzyme PG dehydrogenase, which was highest in chorion and was 2- to 3-fold more active for PGE2 than PGF2 alpha. The activity increased significantly around the time of labor onset. The activity of PG-9-ketoreductase, which interconverts the E and F series of PGs, was 2-3 orders of magnitude less than that of PG dehydrogenase. Using a dual chamber perfusion apparatus, we demonstrated that similar amounts of PGE2 were secreted from the fetal (amnion) and maternal (chorio-decidua) surfaces, and this ratio did not change with labor. Using radiolabeled PGE2, radioactivity traversed full thickness membranes at the rate of 4%/h. Only approximately 12% of the transferred radioactivity remained as intact PGE2, and very little conversion to PGF2 alpha was detected. No changes in transfer were detected around the onset of labor. We conclude that it is unlikely that PGE2 produced in the amnion acts directly on the myometrium.

Amnion↗

PubMed1989

Cervical score and onset of spontaneous labor in prolonged pregnancy dated by second-trimester ultrasonic scan.

The interval from expected day of delivery to spontaneous onset of labor was correlated with parity and cervical score in 103 women with uncomplicated prolonged pregnancy (greater than 294 days). All women had a routine ultrasonic scan in weeks 16-18 for the purpose of dating. The mean (+/- SD) modified Bishop score on entry to the study was 4.15 +/- 2.0 for nulliparas and 4.90 +/- 2.1 for multiparas. The duration beyond 294 days to spontaneous onset of labor varied little (mean 3.5-4.5 days) for nulliparas with scores greater than 2 and for multiparas regardless of score. Nulliparous women with a poor score (less than 3) had spontaneous onset of labor and delivery within a mean of 9.8 days. Half of the multiparas (50.0%) and 43.9% of the nulliparas gave birth within 3 days. About 90% of all women gave birth within 7 days. All but three had a vaginal delivery; the instrumental vaginal delivery rate was 16.3%. The results suggest that in postterm women dated with a second-trimester ultrasonic scan, the cervical scores are in general more favorable than previously reported in series not dated with early scans. The postterm group is also much smaller, and the time interval from entry into the postterm period to spontaneous onset of labor is shorter.

Cervix Uteri↗

PubMed1982

The prostaglandin synthase inhibiting ability of maternal plasma and the onset of human labor.

Using an enzyme incubation-radioimmunoassay technique we have cross-sectionally studied the prostaglandin synthase inhibiting ability of plasma in relation to human pregnancy. The inhibitory potency of human plasma did not change with the onset of pregnancy, at parturition or during the puerperium. A significant decrease in potency did occur however in the third trimester of pregnancy. This preparturient decrease raises the possibility of a role in the onset of human labor for the factor(s) causing the inhibition.

Adult↗

PubMed1979

Sexual behavior and response in relation to complications of pregnancy.

A detailed written questionnaire survey of 155 puerperas is reviewed. Sexual and obstetric data were examined for possible associations leading to premature or low-birth-weight infants. Among 25 patients delivering premature infants (16 with babies weighing less than 2,500 grams), no significant association could be made between coitus, orgasm, and/or other sexual experiences and the proximity to the onset of labor. Orgasmic patients appeared to have a consistently lower percentage of early deliveries. No particular method of sexual gratification was unique except that masturbation was consistently associated with a lower risk of prematurity throughout various stages of gestation. Speculations are advanced to explain these observations. Sexual activity appears to be safe throughout pregnancy in almost all patients. Ruptured membranes on admission may be associated with recent sexual stimulation without orgasm.

Adolescent↗

PubMed1997

Tumor necrosis factor-beta in human pregnancy and labor.

The aims of this study were to determine tumor necrosis factor-beta (TNF-beta) concentration profiles in peripheral venous plasma and amniotic fluid during pregnancy and at the time of labor and to characterise TNF-beta mRNA expression and TNF-beta release from human gestational tissues. In addition, we investigated the expression of TNF-beta binding protein, lymphotoxin-beta (LT-beta), in human gestational tissues. The mean (+/-S.E.M.) TNF-beta concentrations in maternal plasma (TIL, 78 +/- 12 pg/ml, n = 7 vs. TNIL, 304 +/- 88 pg/ml, n = 7) and amniotic fluid (TIL, 8 +/- 5 pg/ml, n = 6 vs. TNIL, 73 +/- 20 pg/ml, n = 20) were significantly (P < 0.05) decreased in association with term labor-onset (TIL) compared to term not-in-labor (TNIL). TNF-beta concentration in maternal plasma and amniotic fluid did not change significantly either with preterm labor (PIL), or during pregnancy. Group-matched comparison of maternal plasma and amniotic fluid TNF-beta concentrations demonstrated that amniotic fluid TNF-beta concentrations were 6-8 fold lower than maternal plasma TNF-beta concentrations. Furthermore, no detectable TNF-beta was secreted from cultured human amniotic, choriodecidual and placental explants. Although, TNF-beta mRNA was detected in amnion, choriodecidual and placenta, LT-beta was similarly expressed in these tissues, suggesting that TNF-beta may be cell membrane bound. These data demonstrate that TNF-beta is present at low levels within the intrauterine environment and may suggest that TNF-beta is specifically inhibited at the maternal-fetal interface.

Amniotic Fluid↗

PubMed1997

Preeclampsia and preterm birth subtypes in Nova Scotia, 1986 to 1992.

The goal of this study was to evaluate the influence of preeclampsia on preterm delivery, examining whether the association varied among preterm birth subtypes defined by gestational age and precipitating events. A population-based, longitudinal study of the association between mild and severe preeclampsia and preterm birth subtypes was conducted among 59,851 women (resulting in a total of 78,086 pregnancies) delivering singleton live births in the province of Nova Scotia, Canada between 1986 and 1992, utilizing the Nova Scotia Atlee perinatal database. Very preterm (< 33 weeks' gestation) and moderately preterm (33-36 weeks' gestation) births were further classified as occurring due to (1) membrane rupture, (2) medical intervention, and (3) spontaneous onset of labor (before membrane rupture). Mild and severe preeclampsia occurred in 8.7 and 1.7% of pregnancies, respectively, after exclusions of multiple births. After adjustment for confounders by multivariable logistic regression based on the generalized estimating equations, severe preeclampsia was strongly associated with the risk of very preterm birth (RR = 80.8, 95% CI: 54.2-120.6), and moderately preterm birth (RR = 41.8, 95% CI: 34.0-51.4) due to medical intervention. A less dramatically elevated risk of very preterm (RR = 2.1, 95% CI: 1.1-4.0) and moderately preterm (RR = 2.2, 95% CI: 1.7-2.9) birth due to medical intervention was apparent among pregnancies complicated by mild preeclampsia. Very preterm births due to membrane rupture were too rare to examine, but moderately preterm births due to membrane rupture were not associated with preeclampsia. Preeclampsia was associated with an increase in the risk of moderately preterm births due to spontaneous labor (RR = 1.9, 95% CI: 1.3-2.8), but not very preterm births (RR = 1.0, 95% CI: 0.7-1.2). Substantial variability was observed in the association between preeclampsia and preterm birth in relation to the subtypes defined by gestational age and pathway, with strong associations between hypertension and medically induced preterm births. The results indicate a need to separate preterm births into subcategories to properly evaluate the association between preeclampsia and preterm births and interventions to reduce the adverse effects of preeclampsia.

Adult↗

PubMed2005

The placental RCAS1 expression during stillbirth.

BACKGROUND: Independently of the fetal death cause the beginning and course of stillbirth is closely related with the growing cytotoxic activity at the maternal-fetal interface. RCAS1 participates in the inhibition of maternal immune response during pregnancy. The alterations of RCAS1 protein expression in placental cells seem to determine the beginning of the labor and participate in the placental abruption. The aim of the present study was to investigate RCAS1 expression in placentas obtained following stillbirths or normal term births. METHODS: RCAS1 expression was evaluated by Western blot method with the use of monoclonal anti-RCAS1 antibody in 67 placental tissue samples. Pregnant women were divided into four groups according to the mode of labor onset--spontaneous or induced, and the type of labor, stillbirth or labor at term. Placental beta-Actin expression was chosen as a control protein. Relative amounts of placental RCAS1 were compared with the use of Student's t-test, whereas beta-Actin control data were compared with the use of Mann-Whitney U test. RESULTS: The average relative amount of RCAS1 was significantly lower in women with induced stillbirths than in women with induced labor at term. Similarly, significantly lower RCAS1 placental levels were observed in patients with spontaneous stillbirths than in women with spontaneous labor at term. Significant differences in RCAS1 expression were also observed with the respect to the beginning of the stillbirth: spontaneous and induced. Lowest RCAS1 placental levels were observed in women with spontaneous stillbirth. CONCLUSIONS: These preliminary results indicate that the alterations of RCAS1 expression in the human placenta may be involved in the changes of maternal immune system that take place during stillbirth.

Adult↗

PubMed1984

Retrograde time-scale analysis of human placental lactogen, beta human chorionic gonadotropin, and unconjugated estriol levels in human maternal serum from the onset of spontaneous labor.

We analyzed on a retrograde time scale which calculated in maternal serum, from the onset of spontaneous labor, human placental lactogen (hPL), beta human chorionic gonadotropin (beta-hCG), unconjugated estriol (E3) levels, and the ratios among these hormones in the normal late pregnancy. Maternal serum hPL, beta-hCG, and unconjugated E3 levels were measured simultaneously and serially in regular menstrual sera from 27 women in late pregnancy (total 155 samples) by radioimmunoassay. The peak level of hPL was found at 2 weeks before labor, and the peak of beta-hCG was found during 2-4 weeks before the onset of spontaneous labor. On the other hand, the mean level of E3 rose slightly with advancing gestational age. The hormonal ratios of hPL to E3 and beta-hCG to E3 decreased gradually toward the onset of labor, but the ratios of hPL to beta-hCG did not change. From these data, it is possible to conclude that the onset of spontaneous labor can be predicted by measuring the levels of hPL and unconjugated E3 in maternal peripheral serum.

Chorionic Gonadotropin↗

PubMed1987

Evaluation of the weekly cervical examination in a preterm birth prevention program.

The efficacy of regular cervical examinations in detecting preterm labor, as well as possible risks, was studied for 133 preterm labor patients who had received regular cervical examinations as part of a preterm birth prevention program. When compared to all other patients experiencing preterm labor during the study period, the rates of preterm premature rupture of the membranes, chorioamnionitis, and postpartum endomyometritis were not increased. For 95 patients with preterm labor within 7 days of a routine cervical examination, labor onset was not temporally associated with the preceding examination. Preterm labor was diagnosed in 18 asymptomatic patients (18.2%) when the weekly examination revealed cervical change. Routine cervical exams, therefore, did not increase morbidity, and for some patients identified preterm labor before symptoms appeared.

Cervix Uteri↗

PubMed1998

Opposing actions of prostaglandins and oxytocin determine the onset of murine labor.

Prostaglandins (PGs) have been recently proven essential for parturition in mice. To dissect the contributions of the two cyclooxygenase (COX) isoforms to the synthesis of PGs during pregnancy, we have characterized the parturition phenotype of COX-1-deficient mice. We find that mice with targeted disruption of the COX-1 gene have delayed parturition resulting in neonatal death. Results of matings of COX-1-deficient females with COX-1 intact males, and blastocyst transfer of COX-1-deficient or -intact embryos into wild-type foster mothers, proved necessity and sufficiency of maternal COX-1 for the normal onset of labor. COX-1 expression is induced in gravid murine uterus and by in situ hybridization; this induction is localized to the decidua. Measurement of uterine PGs further confirmed that COX-1 accounted for the majority of PGF2alpha production. To evaluate the interaction of PGs with oxytocin during murine labor, we generated mice deficient in both oxytocin and COX-1. Surprisingly, the combined oxytocin and COX-1-deficient mice initiated labor at the normal time. COX-1-deficient mice demonstrated impaired luteolysis, as evidenced by elevated serum progesterone concentration and ovarian histology late in gestation, and delayed induction of uterine oxytocin receptors. In contrast, simultaneous oxytocin and COX-1 deficiency restored the normal onset of labor by allowing luteolysis in the absence of elevated PGF2alpha production. These findings demonstrate that COX-1 is essential for normal labor in the mouse, with a critical function being to overcome the luteotrophic action of oxytocin in late gestation.

Animals↗

PubMed1999

Station at onset of active labor in nulliparous patients and risk of cesarean delivery.

OBJECTIVE: To determine whether term nulliparas with an unengaged vertex presentation at onset of active labor have a higher risk for cesarean delivery. METHODS: A retrospective cohort of 1250 randomly chosen nulliparous patients at 37-42 weeks' gestation who delivered between 1988 and 1989 were selected. Four hundred forty-seven patients were excluded because of nonvertex presentation, cesarean delivery before active phase of labor, multiple gestation, delivery at less than 37 weeks' or greater than 42 weeks' gestation, induction of labor, or missing charts. For the purpose of this study, active labor was defined as regular contractions with cervical dilatation of at least 3 cm. The station at onset of active labor was recorded. Engagement was considered to be at station 0 or below. RESULTS: Of the 803 patients in the study group, 567 presented unengaged and 236 patients presented engaged. The cesarean rates differed significantly between the two groups: 14% of those unengaged compared with 5% of those engaged (chi2 = 11.9, P < .001). After adjusting for confounding variables, engagement at the time of onset of active labor was associated with lower risk of cesarean delivery (odds ratio .512, 95% confidence interval .285, .922). CONCLUSION: Eighty-six percent of nulliparas with an unengaged vertex at onset of active labor delivered vaginally. Engaged vertex at the onset of active labor was associated with a lower risk of cesarean delivery.

Cesarean Section↗

PubMed1987

The normal parturient's admission temperature.

The relationship between oral temperature taken at the time of admission and the duration of elapsed labor was evaluated. Onset of labor data revealed a diurnal distribution with an apogee at midnight to 2 AM and a nadir at 11 AM to noon. Temperature data ranged from 94.3 degrees to 99.7 degrees F (34.6 degrees to 37.6 degrees C). The mean temperature of 97.8 degrees +/- 0.8 degrees F (36.6 degrees +/- 0.44 degrees C) is significantly lower (p less than 0.001) than the clinical reference temperature of 98.6 degrees F (37.0 degrees C). A likely explanation is the coincidental admission time (early to late morning) and the nadir of the diurnal variation in temperature. Linear regression fitted to the data (after deletion of six hypothermic outliers) yielded the relationship: temperature = 97.8 degrees F + 0.0115 X duration of elapsed labor (temperature = 36.6 degrees C + 0.0064 X duration of elapsed labor) for which the correlation coefficient is not statistically significant.

Body Temperature↗

PubMed1983

Stimulation of prostaglandin biosynthesis by urine of the human fetus may serve as a trigger for parturition.

Urine of the human fetus stimulated prostaglandin biosynthesis in vitro by increasing the conversion of arachidonic acid into prostaglandins. The stimulatory activity in urine from fetuses delivered at term after labor of spontaneous onset was greater than that in urine from fetuses delivered by cesarean section at term before the onset of labor. Such stimulation of prostaglandin biosynthesis by the fetal membranes, by way of a substance released into the urine and thence into amniotic fluid, could serve as a signal for the initiation of parturition.

Adult↗