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PubMed2004

Term human fetal membranes have a weak zone overlying the lower uterine pole and cervix before onset of labor.

The etiology of fetal membrane (FM) rupture is unknown. A hypothesis that the FM weakens by a process of collagen remodeling and apoptosis to facilitate rupture has been proposed. Human FMs reportedly exhibit a zone of altered histology, postulated to be the FM rupture site, but concomitant FM weakness has not been demonstrated. We hypothesized that a discrete zone of FM with marked weakness, histological change, and evidence of remodeling and apoptosis, develops in late gestation in the FM overlying the cervix. FM tissue from women undergoing prelabor cesarean delivery were perioperatively marked to identify the FM overlying the cervix, cut with a procedure that facilitates remapping the rupture strength of FM pieces to their former location and orientation on a three-dimensional model, and tested for strength. A 10-cm FM zone centered at the cervical mark was compared with the remaining FM. Mean rupture strength within the cervical zone was 55% of the remaining FM. The cervical zone also exhibited increased MMP-9 protein, decreased tissue inhibitor of metalloproteinases-3 (TIMP-3) protein, and increased PARP cleavage coincident with the previously reported zone of altered histology. A discrete zone of weakness is present in term prelabor FMs overlying the cervix and has biochemical characteristics consistent with tissue remodeling and apoptosis.

Apoptosis↗
PubMed1998

[Transvaginal ultrasound assessment of cervical changes before onset of labor].

OBJECTIVE: To study the clinical value of cervical measurement by transvaginal ultrasound after 36 weeks of gestation. METHODS: Eighty three normal nulliparous woman were studied from 36 weeks of gestation until delivery prospectivelly. Transvaginal ultrasound examinations were performed and cervical length (CL), cervical width (CW) and the diameter of cervical canal were measured weekly. 52 cases were delivered naturelly and 31 cases by cesarean sections (CS). RESULTS: From 36 weeks of gestation until delivery, there was a significant correlation between gestation age (GA) and CL and the diameter of cervical canal (r = -0.37, P < 0.00001; r = 0.16, P = 0.002). The time from examination to initiation of labor was significantly correlated with CL and the diameter of cervical canal (r = 0.32, P < 0.00001; r = -0.19, P = 0.02). The regressive formulas were CL (cm) = 13.77 - 0.27 x GA, the time to beginning of labor (week) = 0.64 + 0.54 x CL (cm). The cases with CL > or = 3.5 cm at 2-3 weeks before labor had a significant higher CS rate than those with CL < or = 3.5 cm (P = 0.002). CONCLUSIONS: Transvaginal ultrasonographic measurement of CL, CW and the diameter of cervical canal could reflect the maturity of cervix accurately. It could be used as predictors of labor course and outcome of delivery.

Adult↗
PubMed2002

[Use of oxytocin augmentation after spontaneous onset of labor].

BACKGROUND: Use of oxytocin augmentation during labour is not systematically registered in Norway. We wanted to describe the use of oxytocin augmentation in Hammerfest Hospital from 1996 to 2000. MATERIAL AND METHODS: The patient files of all women who delivered in the study period (n = 2,725) were examined retrospectively. After exclusion because of induction of labour, planned Caesarean section, breech delivery, twin delivery and intrauterine fetal death, 2,122 women were included in the study. RESULTS: 490 of 969 nulliparas (51%) and 233 of 1,153 multiparas (20%) were augmented with oxytocin. 203 of the 239 nulliparas (85%) who had epidural anaesthesia and 287 of the 730 nulliparas (39%) without epidural anaesthesia were augmented, compared to 64 of the 96 multiparas (67%) and 169 of the 1,057 multiparas (16%). INTERPRETATION: In the present study, half of the primiparas and one fifth of the multiparas had their labour augmented with oxytocin. It is not known whether this is representative nationwide. There is a need for more research about dystocia, when intervention is appropriate and which women will benefit from oxytocin augmentation.

Adult↗
PubMed1990

[Weather front sensitivity as an influencing factor in the onset of labor].

The connection between meteorological stimuli and the onset of labor was examined on the basis of the patients' front-sensitivity. Front-sensitivity was tested by a questionary containing 60 questions. Converse relation was observed between the degree of sensitivity and the gestational age. A sudden rise of onsets of labors could be shown during frontal changes, occurred after meteorologically quiet periods. During frontal changes the ratio of onsets of labors rose significantly among those patients who were sensitive tho the given front. This effect could be observed during a longer period of frontal influence. By the authors opinion also meteorological stimuli can be regarded as one of the factors, determining the actual date of onset of labor among front-sensitive women.

Female↗
PubMed2005

Up-regulation of the progesterone receptor (PR)-C isoform in laboring myometrium by activation of nuclear factor-kappaB may contribute to the onset of labor through inhibition of PR function.

Progesterone acting via the progesterone receptor (PR) plays a critical role in maintaining uterine quiescence during pregnancy. In the present study, we tested the hypothesis that the transactivating capability of the PR is down-regulated in the myometrium at term by a change in uterine PR isoform ratio resulting from local activation of the nuclear factor (NF)-kappaB pathway. Overexpression of the truncated PR-C isoform in human myometrial cells inhibited PR-B transactivation. Expression of PR isoforms, PR-A, PR-B, and PR-C, was characterized by immunoblotting and quantitative PCR (Q-PCR) in fundal and lower uterine segment myometrium from pregnant women in labor and not in labor and in the pregnant mouse uterus during late gestation. We observed a marked increase in levels of PR-C and transcriptionally active PR-B specifically in fundal myometrium of women in labor. In pregnant mouse uterus, levels of PR-B and PR-C also increased between 15 days post coitum and term, whereas expression of PR-A was dramatically up-regulated at 19 days post coitum. In studies of uterine tissues of mice injected intraamniotically with surfactant protein A and of human myometrial and T47D breast cancer cells in culture, up-regulation of PR isoform expression was observed in response to activation of the NF-kappaB pathway. Chromatin immunoprecipitation analysis revealed IL-1beta induced binding of NF-kappaB to the PR promoter. Collectively, these findings suggest that up-regulation of inhibitory PR isoform expression by NF-kappaB activation in both laboring human fundus and pregnant mouse uterus near term may inhibit PR transactivation and thereby lead to a loss of uterine quiescence and the onset of labor.

Animals↗
PubMed1999

The relationship between the onset of labor mechanisms and the hemostatic system.

The relationship between onset of labor and the hemostatic system was evaluated in 38 pregnant women. The hemostatic system consists of blood coagulation, kinin-kallikrein system, the fibrinolytic system, and platelet function. The most prominent changes take place in the kinin-kallikrein system. After the onset of labor, prekallikrein decreases rapidly which may trigger changes in blood coagulation and the fibrinolytic system. Platelet hemostatic capacity (PHC) was also measured using the PFA-100 (platelet function analyzer) system. Closure times (CT) were shorter during pregnancy, compared to non-pregnant controls, suggesting an increase in PHC. Platelet aggregation by ADP at the end of pregnancy was decreased at the onset of labor. At the same time a slight increase in FDP (fibrin degeneration product) was also seen. While FDP increased, platelet aggregation decreased, which seems to suggest FDP inhibits platelet aggregation. In this manner, these three systems(kinin-kallikrein system, blood coagulation, and fibrinolytic system) and platelet aggregation are closely interrelated, possibly affecting uterine contractility during pregnancy and the onset of labor.

Factor XII↗
PubMed1987

In vitro conversion of pregnenolone to progesterone in human term placenta and fetal membranes before and after onset of labor.

To determine the role of placental progesterone in the onset of labor, tissue progesterone concentrations and in vitro conversion of tritiated pregnenolone to progesterone were examined in the placentas, chorion, and amnion of 12 term pregnancies delivered by cesarean section with or without labor and vaginal delivery. In all instances, the placenta had significantly higher progesterone concentrations than the chorion or amnion. Progesterone concentrations in the chorion were significantly lower after the onset of labor than before. The placenta and chorion but not the amnion converted pregnenolone to progesterone; the placenta had a significantly greater conversion rate than the chorion in all instances. Placental conversion of pregnenolone to progesterone increased significantly after labor to reach a maximum with vaginal delivery. Chorionic conversion of pregnenolone to progesterone was significantly increased after vaginal delivery but was similar after cesarean section with or without labor. The reduced tissue progesterone in the chorion, together with enhanced placental and chorionic production of progesterone from its precursor, pregnenolone, suggest that rapid metabolism and increased binding of progesterone locally in the placenta and membranes may lead to the local withdrawal or decline of progesterone and onset of labor.

Cesarean Section↗
PubMed1981

[Relationship between the onset of labor and prostaglandins in rabbit tissues before and after delivery (author's transl)].

1) The studies were performed to elucidate the mechanism of onset of labor. It was investigated in relation to the movement of prostaglandins in individual tissues of pregnant rabbits before and after labor with the onset of labor. 2) The rabbit uterus duplex used is convenient material to investigate the movement of PGs in the same rabbit at the different term. 3) The concentrations of PGs were measured by RIA. 4) The concentrations of PGs in blood and amniotic fluid were not essential to explain account for the mechanism of onset labor. 5) From the results of the PGs values before and after labor, we have been considered that the relative PGs at the onset of labor were PG E1 and PG E2 in the placenta. We infer that PG F2 alpha plays a leading role in uterine contraction, because the large amount of PG F2 alpha presented in decidual parietalis during delivery, and PG E1 and PG E2 play a role in uterine contraction, too.

Amniotic Fluid↗
PubMed2006

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

PROBLEM: Granulocyte-macrophage colony-stimulating factor (GM-CSF) at the implantation site may regulate invasion and differentiation of placental trophoblast. We evaluated whether GM-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 36 Japanese women experiencing normal pregnancies with single fetuses who had no infection. Of these pregnancies, 18 were women during labor that led to subsequent term delivery (labors). The other 18 were women without labor underwent cesarean section (controls). These two groups (18 labors and 18 controls) were compared. The average gestational age at entry was 38-39 weeks of gestation. The women's ages and gestational ages did not differ significantly between the two groups. Amniotic fluid was collected and the GM-CSF levels were compared between two groups. The GM-CSF level was determined by the enzyme-linked immunosorbent assay method. RESULTS: There was no significant increase in GM-CSF levels in amniotic fluid during labor compared with that before the onset of labor. CONCLUSIONS: The GM-CSF in amniotic fluid may not promote the onset of labor at term and/or term labor contributing to subsequent delivery may not induce the production and secretion of GM-CSF into amniotic cavity.

Amniotic Fluid↗
PubMedDate not supplied

Association between significant decrease in barometric pressure and onset of labor.

To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure.

Adult↗
PubMed2000

[Correlation between epidermal growth factor receptor messenger RNA expression and the onset of labor].

OBJECTIVE: To study the correlation between epidermal growth factor receptor messenger RNA expression and the onset of labor. METHOD: Semiquantitative reverse transcriptase polymerase chain reaction, using GAPDH as internal standard, was applied to determine the levels of epidermal growth factor receptor messenger RNA in human myometrium (n = 20) and fetal membranes (n = 20) before and during labor. RESULTS: In myometrium, epidermal growth factor receptor messenger RNA increased from 0.91 +/- 0.32 before labor to 1.33 +/- 0.23 after the onset of labor (P < 0.05). In fetal membranes, epidermal growth factor receptor messenger RNA increased from 1.05 +/- 0.30 before labor to 1.65 +/- 0.71 after the onset of labor (P < 0.05). CONCLUSION: The study indicates it is Up-regulation of epidermal growth factor receptors messenger RNA expression in myometrium and fetal membrane before and after the onset of labor.

Amnion↗
PubMed1989

[Kinetics of catecholamines in amniotic fluid implicated with onset of labor pain].

There are several controversies related to labor initiation in term. I therefore tried to analyse the relationship between the onset of labor and the dynamics of catecholamine-concentrations in amniotic fluid using the LC-EC method. Results are as follows. 1. Dopamine levels in amniotic fluid increased with gestational age. 2. Norepinephrine and Dopamine levels were higher in women with uterine contraction than in those without uterine contraction. 3. PGF2 alpha production in amnion increased significantly when it was incubated thirty minutes with CAs compared to that incubated only with Hanks' BSS. The PGE production rate in amnion was five or six times as great as that in PGF2 alpha. In conclusion, it is supposed that CAs in amniotic fluid may play a role in the initiation of uterine contraction.

Amnion↗
PubMed1985

Respiratory morbidity benefit of awaiting onset of labor after elective cesarean section.

Respiratory morbidity in term neonates is an important complication of elective cesarean delivery. The effect of preceding labor on the incidence and severity of respiratory morbidity in two comparable groups of neonates, 107 with and 80 without labor and with no predisposing factors to respiratory morbidity, was evaluated. Transient tachypnea of the newborn accounted for the majority of cases in term neonates. Respiratory morbidity occurred less frequently in neonates delivered after the onset of labor compared with those delivered before labor (11.2 versus 30%, P less than .002). The risk of respiratory morbidity decreased 1.5 times for each week of advancing gestational age. The presence of labor significantly reduced the risk of respiratory morbidity, independently of gestational age (P less than .03), and disease was less severe in neonates born during labor. Awaiting the onset of labor appears to be beneficial in preventing respiratory morbidity in term neonates delivered by elective cesarean section.

Adult↗
PubMed1988

Steroid sulfohydrolase activity in human chorion. I. Interactions of other steroids with estrone sulfate as substrate.

Human chorion contains steroid sulfohydrolase activity and synthesizes free estrogens from estrone sulfate (E1S). We hypothesized that the free estrogen thus formed may influence the contractility of the adjacent myometrium in late pregnancy. In this study we measured the abilities of various steroids and steroid conjugates to influence the hydrolysis of E1S by the 105,000 x g pellet of chorion tissue obtained from women after spontaneous onset of labor and vaginal delivery and from women delivered by cesarean section before labor onset. No differences were found in tissues obtained before or after the onset of labor. None of the steroids increased the rate of hydrolysis. Several unconjugated steroids caused significant inhibition, but only at concentrations well beyond physiological ranges in maternal or fetal blood. However, conjugated steroids had marked inhibitory effects at circulating concentrations. At equimolar concentrations with the E1S substrate, the sulfoconjugates of dehydroepiandrosterone, pregnenolone, and cholesterol caused 27 +/- 1% (+/- SE), 64 +/- 1%, and 40 +/- 1% inhibition, respectively. These results were confirmed using a tissue explant system. Using enzyme inhibition kinetic analysis, we determined that the inhibition by dehydroepiandrosterone sulfate was non-competitive, with Ki = 8.7 +/- 1.7 mumol/L. The inhibition by pregnenolone sulfate was competitive, with Ki = 1.6 +/- 0.4 mumol/L, and that by cholesterol sulfate was primarily noncompetitive, with Ki = 7.4 +/- 1.2 mumol/L. We conclude that there is significant interaction among sulfurylated steroids that may influence local free estrogen synthesis within human chorion. This interaction may affect the contractility of the late pregnancy myometrium.

Chorion↗
PubMed1987

The maternal serum cortisol levels after onset of labor.

We measured maternal cortisol levels after the onset of labor. Blood from 82 primiparas and 48 multiparas were collected 124 times and 60 times, respectively. When duration of labor was within 3 hr, there were no differences in cortisol levels between the primiparous (n = 11, 50.4 +/- 7.0 micrograms/100 ml, mean +/- S.E.) and multiparous (n = 14, 37.8 +/- 4.3 micrograms/100 ml). However, when duration of labor was from 3 to 6 hr, cortisol levels in the primiparas (n = 20, 59.7 +/- 5.1 micrograms/100 ml) were significantly (p less than 0.05) higher than those in the multiparas (n = 22, 46.8 +/- 2.9 micrograms/100 ml). In cases of duration of labor from 6 to 9, cortisol level of the primiparas (n = 24, 64.3 +/- 4.4 micrograms/100 ml) were also significantly (p less than 0.05) higher than those in multiparas (n = 12, 49.4 +/- 4.7 micrograms/100 ml). When duration of labor was more than 9 hr there was no significant difference in cortisol level between the primiparas and multiparas. Maternal cortisol level had a significant (p less than 0.01) negative correlation (n = 166, r = -0.243, Y = -0.09X + 30.47) with unconjugated estriol level. These data suggest that maternal cortisol levels after the onset of labor are slightly different between the primiparous and multiparous, and that maternal unconjugated estriol levels decrease owing to reduction of the feto-placental blood circulation accompanied with uterus contraction during labor.

Female↗
PubMed2005

Urinary cyclic guanosine 3',5'-monophosphate and cyclic adenosine 3',5'-monophosphate changes in spontaneous and induced onset active labor.

BACKGROUND: The aim of this prospective, randomized study was to investigate the changes in urinary cyclic guanosine 3',5'-monophosphate (cGMP) and cyclic adenosine 3',5'-monophosphate (cAMP) between the latent and the active phases of spontaneous and prostaglandin E(1) (PGE(1))-induced labor. METHODS: Seventy singleton pregnant women at 36-41(+) weeks' gestation without signs of fetal distress were enrolled. The first group consisted of 35 pregnant women in whom labor was induced by PGE(1) applied intravaginally. The second group consisted of 35 women who had spontaneous active labor. Clinical data of the two groups were assessed as labor progressed. RESULTS: After the onset of active labor, urinary cGMP/creatinine (U cGMP/Cr) decreased in both groups with the percentage decline of 35.2 and 9.7, respectively, but this difference was only significant in the PGE(1)-induced group (P=0.033). After the onset of active labor, urinary cAMP/creatinine (U cAMP/Cr) decreased in both groups with the percentage decline of 36.5 and 15.6, respectively, but this difference was only significant in the PGE(1)-induced group (P=0.001). The duration of the latent phase was significantly shortened in the PGE(1)-induced group compared with the spontaneous labor group (P<0.05). CONCLUSIONS: Decreased U cGMP/Cr and U cAMP/Cr may be a transition from the latent to the active phase in PGE(1)-induced labor. Our results suggest that U cGMP/Cr and U cAMP/Cr can serve as easily obtained secondary messenger markers of myometrial contractility and cervical ripening at the onset of active labor. The NO-cGMP system and the G-protein alpha-cAMP system in the human uterus may concomitantly contribute to uterine quiescence during pregnancy and show downregulation in U cGMP/Cr and U cAMP/Cr at the initiation of active labor.

Adult↗
PubMed1996

The effect of changes in atmospheric pressure on the occurrence of the spontaneous onset of labor in term pregnancies.

OBJECTIVE: Our purpose was to determine whether there is a relationship between changes in atmospheric pressure and spontaneous onset of labor in term pregnancy. STUDY DESIGN: All women admitted to Medical Center of Central Massachusetts-Memorial Hospital with spontaneous onset of labor at term and who were delivered on the service during a 12-month period represent the cohort for this study. Each maternal chart was abstracted to ensure that each member of the cohort met the inclusion criteria. Hourly recordings of atmospheric pressure made at the Worcester Station of the National Weather Service, Department of Commerce, were used as the meteorologic data points of interest. Least-squares regression was used to determine an equation that expresses the probability of the onset of labor in this cohort as a function of gestational age, which was used to calculate expected numbers for the statistical analyses. Two relationships were studied: (1) the ratio of the observed to the expected number of onsets of labor and (2) the initiation of labor and atmospheric pressure changes in the preceding 3 hours. RESULTS: Three-hour periods of falling atmospheric pressure were less often followed by initiation of labor than were the periods with other types of pressure sequences. No association was observed between the onset of labor and days of low mean pressure. CONCLUSION: Although there was an observed statistically significant association between falling barometric pressure and onset of labor, the magnitude of the difference is not of clinical significance.

Atmospheric Pressure↗
PubMed2006

Bishop score and ultrasound assessment of the cervix for prediction of time to onset of labor and time to delivery in prolonged pregnancy.

OBJECTIVES: To determine the ability of Bishop score and sonographic cervical length to predict time to spontaneous onset of labor and time to delivery in prolonged pregnancy. METHODS: Ninety-seven women underwent transvaginal ultrasound examination and palpation of the cervix at 291-296 days' gestation according to ultrasound fetometry at 12-20 weeks' gestation. Sonographic cervical length and Bishop score were recorded. Multivariate logistic regression analysis was used to determine which variables were independent predictors of the onset of labor/delivery < or = 24 h, < or = 48 h, and < or = 96 h. Receiver-operating characteristics (ROC) curves were drawn to assess diagnostic performance. RESULTS: In nulliparous women (n = 45), both Bishop score and sonographic cervical length predicted the onset of labor/delivery < or = 24 h and < or = 48 h (area under ROC curve for the onset of labor < or = 24 h 0.79 vs. 0.80, P = 0.94; for delivery < or = 24 h 0.81 vs. 0.85, P = 0.64; for the onset of labor < or = 48 h 0.73 vs. 0.74, P = 0.90; for delivery < or = 48 h 0.77 vs. 0.71, P = 0.50). Only Bishop score discriminated between nulliparous women who went into labor/delivered < or = 96 h or > 96 h. A logistic regression model including Bishop score and cervical length was superior to Bishop score alone in predicting delivery < or = 24 h (area under ROC curve 0.93 vs. 0.81, P = 0.03) and superior to Bishop score alone and cervical length alone in predicting the onset of labor < or = 24 h (area under ROC curve 0.90 vs. 0.79, P = 0.06; and 0.90 vs. 0.80, P = 0.06). In parous women (n = 52), Bishop score and sonographic cervical length predicted the onset of labor/delivery < or = 24 h (area under ROC curve for the onset of labor 0.75 vs. 0.69, P = 0.49; for delivery 0.74 vs. 0.70, P = 0.62), but only Bishop score discriminated between women who went into labor/delivered < or = 48 h and > 48 h. Three parous women had not gone into labor and six had not given birth at 96 h. In parous women logistic regression models including both Bishop score and cervical length did not substantially improve prediction of the time to onset of labor/delivery. CONCLUSIONS: In prolonged pregnancy Bishop score and sonographic cervical length have a similar ability to predict the time to the onset of labor and delivery. In nulliparous women the use of logistic regression models including Bishop score and cervical length is likely to offer better prediction of the onset of labor/delivery < or = 24 h than the use of the Bishop score alone.

Adolescent↗