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PubMed1997

Type-1 and type-2 cytokines in human late-gestation decidual tissue.

Evidence suggests that successful pregnancy in rodents requires the preferential stimulation of type-2 cytokine production by gestation-associated tissues. The ability of human gestation-associated tissue to synthesize type-2 and type-1 cytokines has not been examined in detail and was the subject of this study. Decidual tissue collected at term, either before the onset of labor (elective caesarean section) or at the completion of labor, expressed mRNA for interleukin (IL)-10 and interferon gamma (IFN-gamma) and produced IL-10 and IFNgamma protein in vitro. IL-4 mRNA or protein was not detected. IFNgamma production in vitro was significantly decreased by decidual cells prepared from decidua collected after labor as compared with those collected before the commencement of labor, a change that may be associated with prostaglandin E2 (PGE2) production in conjunction with labor. IFNgamma, IL-4, and IL-10 were detectable in human amniotic fluid collected at term. There was no significant difference in the levels of IL-4, IFNgamma, or IL-10 in samples collected before labor onset or during labor. Thus, late-gestation human decidual tissue and amniotic fluid do not preferentially express a type-2 cytokine profile of cytokines. This is not consistent with observations of a predominant type-2 cytokine profile in gestation-associated tissues in murine pregnancy.

Amniotic Fluid↗
PubMed1983

The role of estradiol and progesterone in the regulation of myometrial activity for the onset of labor.

The concentrations of estradiol (E2) and progesterone (P) were measured in peripheral plasma and myometrium from women in the 35th to 42nd week of pregnancy. On the basis of the subjective symptoms and objective signs of labor, judged by tocography and cervical status, the women were divided into two groups, one in labor and the other not. There were no significant inter-group differences in the concentrations of E2 or P in either plasma or the myometrium. The plasma P/E2 ratio, however, differed significantly, being lower in the women in labor. A similar tendency was found in the P/E2 ratio in the myometrium but due to a wide variation, the inter-group difference did not attain statistical significance. The results suggest that a lower P/E2 ratio at term would facilitate the action of an, as yet unknown, physiological stimulus to the onset of labor.

Adult↗
PubMed1996

Asymptomatic maternal shedding of herpes simplex virus at the onset of labor: relationship to preterm labor.

OBJECTIVE: To determine if fetal growth restriction and prematurity are observed with subclinical shedding of herpes simplex virus (HSV) at the onset of labor. METHODS: Within 48 hours of delivery, cultures were taken from the cervix and external genitalia of 15,923 asymptomatic pregnant women without symptoms or signs of genital HSV infection; results were positive for HSV in 57. Each of these 57 women were compared with a control group composed of the three culture-negative women delivering immediately before and the three delivering immediately after each woman shedding HSV. RESULTS: The median birth weight for infants born to the 57 women with asymptomatic shedding was 3050 g, compared with 3360 g among the 342 women without asymptomatic shedding, a statistically significant difference (P < .002). These differences were due to very low birth weight (LBW) among the five infants of women with subclinical viral shedding secondary to recently acquired primary genital herpes; these five infants had a median gestational age of 33 weeks, compared with 37 weeks for the 14 infants of mothers with nonprimary, first-episode disease and 39 weeks for the 33 infants of women with reactivation disease, also a significant difference (P = .018). CONCLUSIONS: Asymptomatic genital shedding of HSV at the onset of labor because of subclinical primary genital HSV infection is associated with preterm delivery. Women who acquire genital HSV-2 before pregnancy and are shedding subclinically at the onset of labor experience no increase in adverse outcome. Thus, prevention of the prematurity and LBW associated with genital herpes means that acquisition of the infection in late pregnancy must be prevented.

Birth Weight↗
PubMedDate not supplied

Recognizing the onset of labor.

An experimental study compared the use of an educational technique based on patient participation with routine instructions to prepare patients to recognize the onset of active labor. The number of visits to the labor suite that resulted in the patient being discharged undelivered was significantly lower in patients who received the educational intervention. The study revealed that, without any increase in time, nurses can prepare patients to make judgments about the need for hospitalization.

Female↗
PubMed1985

[Studies on the alteration of the unconjugated estriol level of the maternal vein after the onset of labor].

We measured maternal venous unconjugated estriol (UE3) levels in 244 cases (218 cases with labor and 26 without labor). We investigated the relationships between several obstetrical factors and UE3 levels. There was no significant difference between the group with labor and the group without labor. However, in multipara, the UE3 level fell gradually with prolonged duration of labor. There were significant positive correlations between the UE3 levels and birth weights (n = 82, r = 0.375, p less than 0.001), and placental weights (n = 82, r = 0.381, p less than 0.001) in multipara with labor. There was no significant difference according to sex between the UE3 levels of a mother carrying a male or female fetus. The UE3 levels of fetal distress cases (n = 30, mean +/- S.E. 20.0 +/- 8.6 ng/ml) were significantly (p less than 0.02) lower than those without fetal distress (n = 188, 24.5 +/- 9.7 ng/ml). These data suggest that after the onset of labor, maternal venous UE3 has some relationship to feto-placental function.

Body Weight↗
PubMed1975

Blood in amniotic fluid following intrauterine transfusion and its effect on premature onset of labor.

The most frequent cause of perinatal death following intrauterine transfusion in cases of severe rhesus hemolytic disease remains premature onset of labor and the resulting newborn so delivered. In the present study, 70% of all perinatal deaths were directly related to immaturity. A factor of decisive importance as an initiator of labor before the intended time is the leakage of blood into the amniotic fluid at the time of the procedure. (Mostly, this blood seems to originate from the fetal abdomen into which it was injected for therapeutic reasons.) The effect of blood-contaminated amniotic fluid on uterine activity is demonstrated on the material from Lewisham Hospital of London, where between 1 and 5 intrauterine transfusions were performed on 517 patients during a period between November 1963 and the end of March 1973. The presence of blood in the amniotic fluid was proved either by means of amniocentesis performed 2 days after intrauterine transfusion, or at the time of membrane rupture in labor. Patients who received a self-retaining catheter for any length of time were excluded from the material since the additive influence of the catheter on labor could not be assessed. Out of a total of 452 cases receiving single-use catheters, there were 208 cases (46%) with premature onset of labor. In 2-thirds of the cases this happened within the first week after the last intrauterinetransfusion. Further investigation of 332 case-histories with complete records was carried out. In 61.6% of the patients with labor before the intended time within 21 days after the last intrauterine transfusion, blood contaminated amniotic fluid was found, whereas this occurred in only 34.8% of the cases without premature onset of labor (p less than 0.001). From the same material, corresponding percentages for livebirths and stillbirths were calculated. As a consequence of these results, it is recommended that patients be kept under intensive hospital care following intrauterine transfusion whenever blood can be proved to be present in the amniotic fluid. Prophylactic measures to prevent premature onset of labor should also be considered.

Amniotic Fluid↗
PubMed2004

Timing of birth after spontaneous onset of labor.

OBJECTIVE: To describe naturally occurring birth patterns in low-risk women with singleton gestations and spontaneous onset of labor at term. MATERIALS AND METHODS: The timing of birth of women who delivered in the low-risk labor unit at Parkland Hospital, Dallas, Texas, between January 1, 2000, to December 31, 2000, was analyzed. Women admitted to this unit were between 36(0/7) and 41(6/7) weeks of gestation, were in spontaneous labor, and had a singleton gestation. Women with contraindications to labor, significant medical problems, a known fetal anomaly, and stillbirths were excluded from analysis. The frequency of birth was analyzed in relation to the time of day, day of week, and month of the year. RESULTS: Low-risk women (n = 6608) met the study criteria and were included in the analysis. No association was found between the day of the week and the frequency of births (P =.31). Births were most common between the hours of 1 to 2 pm and least common between the hours of 10:00 to 12:00 hours (Central Standard Time, P =.04). Births were more common in the fall, September through November, and least common in the winter, December through February. Daylight Saving Time did not affect these results. CONCLUSION: Birth after the spontaneous onset of labor is most common in the early afternoon, and most births occur in the fall. There is no natural association between spontaneous birth in low-risk women and the day of the week. LEVEL OF EVIDENCE: II-2

Adolescent↗
PubMed2004

Urinary nitric oxide metabolite changes in spontaneous and induced onset active labor.

BACKGROUND: The aim of this prospective, randomized study was to investigate the changes in urinary nitric oxide (NO) metabolite between the latent and the active phases of spontaneous and either prostaglandin E(1) (PGE(1)) or prostaglandin E(2) (PGE(2))-induced labors. METHODS: Eighty-eight singleton pregnant women at 36-41(+) weeks' gestation without signs of fetal distress were enrolled. The first group consisted of 29 pregnant women in whom labor was induced by PGE(1) applied intravaginally. The second group consisted of 29 pregnant women with labor induced by PGE(2) applied intracervically. The third group consisted of 30 women, who had spontaneous active labor. Clinical data of the three groups were assessed as labor progressed. RESULTS: Urinary nitric oxide/creatinine (U NO/Cr) decreased significantly after the onset of active labor in all three groups (p < 0.005), with the percentage decline of 42.2%, 28.6% and 10.1%, respectively. The magnitude of the difference in decline in U NO/Cr after active labor between the PGE(1)-induced and the spontaneous labor group was significantly reduced (p = 0.0047) after adjustment for potential confounders using the generalized estimating equations test (GEE). The duration of the latent phase was significantly shortened in the PGE(1)-induced group as compared with the spontaneous labor group (p < 0.01). CONCLUSIONS: Decreased U NO/Cr may facilitate transition from the latent to the active phase either in spontaneous or induced labors. Our results indicate that U NO/Cr can serve as an easily obtained marker for use in controlling myometrial contractility and cervical ripening at the onset of active labor. The nitric oxide system is present in the human uterus and may contribute to uterine quiescence during pregnancy and show down-regulation in U NO/Cr at the initiation of active labor.

Administration, Intravaginal↗
PubMed2004

Macrophage colony-stimulating factor levels in amniotic fluid before and after the onset of labor do not differ in normal pregnancies.

PROBLEM: Macrophage colony-stimulating factor (M-CSF) promotes placental growth and maintenance. M-CSF also regulates trophoblast invasion into the placental bed. We evaluated whether M-CSF levels in amniotic fluid during labor contributing to subsequent delivery differed from those before the onset of labor in normal pregnancies. METHOD OF STUDY: This study enrolled 48 Japanese women experiencing normal pregnancies with single fetuses who had no infection. Of these pregnancies, 24 were women during labor: 22 led to subsequent term delivery (labors); two had premature delivery. The other 24 were women without labor underwent cesarean section (controls). These two groups (22 labors and 24 controls) were compared. The average gestational age at entry was 38 weeks of gestation. The women's ages and gestational ages did not differ significantly between the two groups. Amniotic fluid was collected and the M-CSF levels were compared between two groups. The M-CSF level was determined by the sandwich enzyme-linked immunosorbent assay (ELISA) method. RESULTS: The levels of M-CSF in amniotic fluid did not differ significantly between the women during labor and those without labor. CONCLUSIONS: M-CSF in amniotic fluid may not contribute to the onset of labor in term pregnancy and/or labor resulting in subsequent delivery may not induce the production and secretion of M-CSF into amniotic cavity.

Adult↗
PubMed1990

A comparison of the ability of a sonographically measured biparietal diameter and the last menstrual period to predict the spontaneous onset of labor.

To study whether the estimated date of confinement (EDC) for women with optimal menstrual histories is predicted best from the last menstrual period (LMP) or biparietal diameter (BPD), 2320 women had the EDC estimated by both LMP and BPD measured sonographically in the second trimester. Those who delivered after the spontaneous onset of labor are reported here. Compared with the EDC calculated from the LMP, the EDC calculated from the BPD was postponed more than 1 week for 406 women (17.5%) and advanced more than 1 week for 56 (2.4%). For these women, the BPD estimate of EDC turned out to be closer to the day of delivery in 264 cases, whereas the LMP estimate was closer in 125 (P less than .001). For 73 women, the estimates were equally good. For 80.1% of the women, the two estimates of EDC differed by 1 week or less; in these cases, the estimates were equally good in predicting the day of delivery. We conclude that the BPD is a better predictor of the spontaneous onset of labor than is the LMP.

Clinical Trials as Topic↗
PubMed1988

Intraamniotic infection and the onset of labor in preterm premature rupture of the membranes.

The purpose of this study was to examine the relationship between intraamniotic infection and the onset of labor in patients with preterm premature rupture of the membranes. Two hundred and thirty consecutive patients were admitted with premature rupture of the membranes to Yale-New Haven Hospital from January 1985 to July 1987. Amniotic fluid was retrieved by amniocentesis from 96% (221/230). Sixty-one patients were in labor on admission (27.6%, 61/221) and 39% of them (24/61) had a positive amniotic fluid culture. Patients in labor on admission were more likely to have a positive amniotic fluid culture than those who were not in labor on admission (24/61 versus 41/160, p = 0.049). Of the 160-patients who were not in labor on admission, 81 subsequently went into spontaneous labor; microbiologic information at the time of labor was known in 48 of these patients (59.2%). Seventy-five percent (36/48) of these patients had a positive amniotic fluid culture. The incidence of intraamniotic infection in quiescent women who subsequently went into labor was higher than that of patients admitted in active labor (75% versus 39%, p = 0.0004). These results provide a basis for the clinical impression that the onset of labor in women with preterm premature rupture of the membranes is associated with a subclinical intraamniotic infection. The mechanisms responsible for the onset of labor in women without an intraamniotic infection may be associated with an extraamniotic infection (e.g., deciduitis) or a noninfectious process.

Amniotic Fluid↗
PubMed2006

Three-dimensional ultrasound assessment of the cervix for predicting time to spontaneous onset of labor and time to delivery in prolonged pregnancy.

OBJECTIVES: To determine whether three-dimensional (3D) ultrasound including power Doppler examination of the cervix is useful for predicting time to spontaneous onset of labor or time to delivery in prolonged pregnancy. METHODS: A prospective study was conducted in 60 women who went into spontaneous labor. All underwent transvaginal 3D power Doppler ultrasound examination of the cervix immediately before a prolonged-pregnancy check-up at > or = 41 + 5 gestational weeks. Univariate and multivariate logistic regression analysis was used to determine which of the following variables predicted spontaneous onset of labor > 24 h and > 48 h and vaginal delivery > 48 h and > 60 h: length, anteroposterior (AP) diameter and width of the cervix and of any cervical funneling; cervical volume (cm3); vascularization index (VI); flow index (FI); vascularization flow index (VFI); parity; and Bishop score. Multivariate logistic regression analysis was carried out both with and without Bishop score as a predictive variable. Receiver-operating characteristics (ROC) curves were used to describe the diagnostic performance of the tests. RESULTS: The areas under the ROC curves for Bishop score, cervical length, and logistic regression models did not differ significantly (areas ranging from 0.72 to 0.82). If Bishop score was not included in the logistic regression model, cervical length, VI and FI independently predicted delivery > 48 h, the likelihood increasing with increasing cervical length, decreasing VI and increasing FI. CONCLUSIONS: In prolonged pregnancy cervical vascularization as estimated by 3D power Doppler ultrasound is related to time to delivery > 48 h, but the likelihood of delivery > 48 h can be predicted equally well using Bishop score alone or sonographic cervical length alone.

Adult↗
PubMed1999

Tumor necrosis factor during pregnancy and at the onset of labor and spontaneous abortion.

OBJECTIVE: The aim of this study was to evaluate the production of tumor necrosis factor (TNF) by peripheral blood cells during pregnancy, at the onset of labor and of spontaneous abortion (SA), as well as in non-pregnant women with and without a history of recurrent spontaneous abortions (RSA). STUDY DESIGN: The peripheral blood cells TNF production was evaluated in 28 women in the 1st trimester of pregnancy, 21 in the 2nd, and 30 in the 3rd, 47 at term labor; 43, at the onset of SA; 19 healthy and 19 RSA non-pregnant women. The statistical method used was the Mann-Whitney test. RESULTS: We observed (1) lack of TNF detection in the 1st gestational trimester; (2) increase of TNF production with gestational age, with the highest values being observed at labor (P<0.05); (3) high TNF production at the onset of SA; (4) no difference in the TNF production by healthy and RSA non-pregnant women. CONCLUSIONS: The suppression of TNF production during the 1st trimester of pregnancy seems to favor the normal development of pregnancy. It remains to be investigated whether the assessment of TNF production is a valuable prognostic parameter for the occurrence of abortion.

Abortion, Spontaneous↗
PubMed1991

Cesarean section before the onset of labor and subsequent motor function in infants with meningomyelocele diagnosed antenatally.

Background. Meningomyelocele can now be detected before birth. Few data are available on its natural history, however, and optimal management at the time of delivery is controversial, although it has been suggested that labor and vaginal delivery may cause pressure on exposed nerve roots, resulting in additional loss of neural function. Methods. To assess the effect of labor and the type of delivery on the level of motor function in fetuses with uncomplicated meningomyelocele, we identified 200 cases of this disorder, accounting for 95 percent of the cases that occurred in the state of Washington during our 10-year study period. We compared the outcomes of 47 infants delivered by cesarean section before labor began, 35 delivered by cesarean section after a period of labor, and 78 who were delivered vaginally (another 40 were ineligible for the study). In cases of meningomyelocele detected prenatally, cesarean section was performed before the onset of labor if isolated meningomyelocele without severe hydrocephalus was present. The infants delivered in this manner were compared with those who were delivered either vaginally or by cesarean section after labor began. Results. At two years of age, the infants who had been exposed to labor were 2.2 times more likely to have severe paralysis than those delivered by cesarean section without labor (95 percent confidence interval, 1.7 to 2.8). Infants delivered by cesarean section before the beginning of labor had a mean (+/- SD) level of paralysis 3.3 +/- 3.0 segments below the anatomical level of the spinal lesion at two years of age, as compared with 1.1 +/- 2.3 for infants delivered vaginally and 0.9 +/- 4.1 for infants delivered by cesarean section after the beginning of labor (P less than 0.001 for both comparisons). Exposure to labor did not affect the frequency of neonatal complications or later intellectual performance. Conclusions. For the fetus with uncomplicated meningomyelocele, delivery by cesarean section before the onset of labor may result in better subsequent motor function than vaginal delivery or delivery by cesarean section after a period of labor.

Cesarean Section↗
PubMed1996

Connexin-26 and connexin-43 are differentially expressed and regulated in the rat myometrium throughout late pregnancy and with the onset of labor.

Gap junctions are characteristically increased in the myometrium during term and preterm delivery and are thought to be essential for the development of labor contractions. The expression of connexin-43 (Cx-43), the major myometrial gap junction protein, is increased during delivery (associated with an increase in the plasma estradiol/progesterone ratio) and after estradiol treatment of ovariectomized nonpregnant rats. However, Cx-43 is only 1 member of at least 16 proteins encoded by this family of gap junction genes. Using a RT-PCR method, we identified the presence of another member of this family, Cx-26, in laboring rat myometrium. The temporal expression pattern of Cx-26 was assessed using Northern and Western analyses. In contrast to Cx-43, whose expression is low throughout the pregnancy but increases immediately before the onset of labor (day 23), the expression of Cx-26 increased on day 17, reached maximal levels between days 19-21, and fell to low levels before the onset of labor. Treatment of pregnant rats with progesterone beginning on day 20 (which blocks both the increase in Cx-43 expression and the onset of labor) maintained the elevated expression of Cx-26. Induction of preterm labor in rats after ovariectomy on day 17 inhibited the normal preterm increase in Cx-26 transcripts. Progesterone treatment of these animals reversed the effects of ovariectomy. Immunofluorescence data identified Cx-26 antigen in the cell membranes of myometrial cells and in the luminal and glandular epithelium of the endometrium in the late pregnant (day 21) uterus. These data suggest that the role of gap junction formation in the myometrium in relation to the maintenance of pregnancy and the onset of labor is much more complex than previously recognized. Myometrial cell-cell communication is afforded by at least two different gap junction proteins, Cx-43 and Cx-26, that not only exhibit temporally distinct patterns of expression but are also subject to differential regulation.

Animals↗
PubMed1999

Amniotic fluid volume and onset of labor in physiological pregnancy.

We measure, by means of ultrasound, the amniotic fluid volume (expressed as maximal vertical pocket or MVP) in 646 normal pregnancies at the 39th gestational week. Our aim is to evaluate the possible correlation between MVP and onset of the labor. In a 2-week follow-up, the onset of the labor is considered the "event" variable in a time-dependent statistical analysis. Univariate analysis (Kaplan-Meier algorithm) describes a different trend in predicting the onset of labor when a stratification of MVP < 50 and > or = 50 mm was performed (chi2 = 7.91 p < 0.0049 with 1 df, Breslow-Gehan test). The first category was comprised of 496 fetuses with a median (min-max) MVP of 39 mm (25-49), the second category of 150 fetuses with a MVP of 57 mm (50-100). The results suggest that lower levels of MVP are associated to a higher percentage of the onset of labor. Furthermore, in our measurement, performed at the 39th gestational week, the correlation with the events is higher within the 40th gestational week. In fact, at 7 days from the amniotic fluid measurement, the onset of labor and the subsequent delivery is observed in 80.65 and 73.00% of the cases when they are stratified according to MVP < 50 and > or = 50 mm. At the end of the follow-up, instead, the percentage of "events" is similar, 88.10 and 86.67%, respectively. Adjustment for covariates (Cox analysis), as well as maternal age, neonatal weight, and obstetrics history, show an odds ratio (95% C.I.) of 2.08 (1.61-2.69) for MVP, using the above cutoff level. In physiological pregnancy, lower levels of amniotic fluid at term correlated to a higher probability of the onset of labor.

Adolescent↗
PubMed1999

Myometrial nitric oxide synthase messenger ribonucleic acid expression does not change throughout gestation or with the onset of labor.

OBJECTIVE: The purposes of this study were to examine expression of nitric oxide synthase isoforms in human myometrium and to determine any changes in expression with gestational age and with the onset of labor at term. STUDY DESIGN: Myometrial samples were collected from patients undergoing cesarean delivery at term before and after the onset of labor (n = 17) and throughout gestation (n = 13). Expressions of inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase were determined by semiquantitative reverse transcriptase-polymerase chain reaction. RESULTS: Messenger ribonucleic acid for inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase is expressed in human myometrium at term and throughout the second and third trimesters. Levels of messenger ribonucleic acid for both inducible, calcium-independent nitric oxide synthase and constitutive, calcium-dependent endothelial nitric oxide synthase do not change with either gestational age or the onset of labor. CONCLUSION: Changes in myometrial nitric oxide synthase expression and thus of levels of endogenous nitric oxide are unlikely to be directly involved in myometrial quiescence or the onset of human parturition.

Calcium↗
PubMed1993

The effects of potassium channel openers on isolated pregnant human myometrium before and after the onset of labor: potential for tocolysis.

OBJECTIVE: Our purpose was to investigate the effects and pharmacologic properties of potassium channel openers in isolated pregnant human myometrium. STUDY DESIGN: Biopsy specimens of myometrium obtained from 67 women during pregnancy and labor were used for isometric recording under physiologic conditions. RESULTS: Levcromakalim and pinacidil, two prototype potassium channel openers, are potent inhibitors of spontaneous and induced (0.5 nmol/L oxytocin and 10 mumol/L phenylephrine) contractions in isolated human pregnant myometrium, obtained before and after the onset of labor. The sulfonylurea glibenclamide is an apparent competitive antagonist of this inhibition. No antagonism was observed with the sulfonylurea tolbutamide. Both potassium channel openers significantly inhibited contractility evoked by low (10 and 20 mmol/L) but not high (40 and 80 mmol/L) concentrations of extracellular potassium chloride. CONCLUSION: These findings suggest that the relaxant ability of levcromakalim and pinacidil in human pregnant myometrium is because of potassium channel activation. This introduces a potential new approach for tocolysis.

Benzopyrans↗