Active-phase labor arrest: oxytocin augmentation for at least 4 hours

OBJECTIVE: To assess a labor-management protocol that mandated at least 4 hours of oxytocin augmentation before cesarean delivery for active-phase labor arrest. METHODS: We prospectively evaluated term gravidas in spontaneous labor with active-phase labor arrest (cervix at least 4 cm dilated and 1 cm or less of cervical progress in 2 hours). Exclusion criteria included nonvertex presentation, previous cesarean, multiple gestation, and a nonreassuring fetal heart rate tracing or chorioamnionitis at the time of labor arrest. After the diagnosis of active-phase arrest, oxytocin was initiated with an intent to achieve a sustained uterine contraction pattern of greater than 200 Montevideo units. Cesarean delivery was not performed for labor arrest until at least 4 hours of a sustained uterine contraction pattern of greater than 200 Montevideo units, or a minimum of 6 hours of oxytocin augmentation if this contraction pattern could not be achieved. RESULTS: Five hundred forty-two women were managed by the protocol, and 92% delivered vaginally. The subsequent vaginal delivery rate for parous women who had not progressed (1 cm of cervical dilation or less) despite 2 hours of oxytocin augmentation was 91%, and it was 74% for nulliparas. With no labor progress after 4 hours of oxytocin augmentation, the subsequent vaginal delivery rates were 88% for parous women and 56% for nulliparas. There were no severe maternal complications. One neonate had persistent fetal circulation and one had a positive blood culture, but both did well. CONCLUSION: Extending the minimum period of oxytocin augmentation for active-phase labor arrest from 2 to at least 4 hours was effective and safe.     

Pulsatile administration of oxytocin for augmentation of labor

In a randomized study, 94 patients with term pregnancies underwent augmentation of labor with either continuous or pulsed (every 8 minutes) intravenous oxytocin infusion. There were no significant differences with respect to the maternal characteristics, cervical dilatation and effacement, induction-to-labor interval, induction-to-delivery interval, cesarean section rate, analgesia for labor, or low Apgar scores. No hyperstimulation was noted in either group. In each group, 20% of the patients had dysfunctional labor patterns, with coupling and tripling of the uterine contractions. The mean +/- SEM oxytocin administered in the pulsed-infusion group was significantly lower than that in the continuous-infusion group (2.1 +/- 0.4 versus 4.1 +/- 0.4 mU/minute; P less than .001). The mean +/- SEM total amount of oxytocin administered was 1300 +/- 332 mU for the pulsed group and 1803 +/- 302 mU for the continuous group, indicating that lower amounts of oxytocin were required for pulsed administration. Our study demonstrates that pulsatile administration of oxytocin is similar in efficacy to our standard continuous oxytocin infusion and requires a lower total amount and rate of oxytocin administered, which may afford a greater margin of safety.     

Oxytocin pharmacodynamics: effect of long infusions on uterine activity

Despite common use in obstetrics for almost 50 years, there is still disagreement concerning optimal clinical protocols for the use of oxytocin. This disagreement arises in part from inadequate data on oxytocin pharmacokinetics and pharmacodynamics. This report evaluates the uterine response to fixed doses of oxytocin (1-3 mIU/min) over long infusion times (up to 120 min) in 10 patients with secondary arrest of dilatation. The uterine activity increased from 132 +/- 61 Alexandria units during the control period to 199 +/- 64 Alexandria units at an infusion rate of 1 mIU/min. Increasing the infusion rate to 2 mIU/min increased the uterine activity to 240 +/- 64 Alexandria units. The uterine activity increased until a steady state was achieved between 40 and 70 min after the initiation of infusion. Continuing the infusion at a fixed rate for more than 90 min appears to result in a decreasing uterine activity. Patients requiring oxytocin for augmentation of labor developed adequate uterine activity with dose rates of 1-3 mIU/min. Clinical protocols for oxytocin augmentation with an interval of 40-60 min between increases in the dosing seem reasonable based on these pharmacodynamic data.     

Rate of increase in oxytocin dose on the outcome of labor induction.

OBJECTIVE: To compare the efficacy and safety of arithmetic and geometric increases in oxytocin infusion dosage during induction of labor. METHODS: A total of 120 pregnant women requiring induction of labor at term were randomly assigned to receive oxytocin at dosages increasing arithmetically or geometrically. Maternal demographics, labor delivery data, and newborn outcomes were compared. The setting was the maternity unit of the Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria. RESULTS: The mean maximum rates of oxytocin delivery needed to achieve adequate uterine contractions were similar in the 2 groups (24.66+/-8.34 mU/min vs. 26.38+/-8.77 mU/min, P=0.24). Labor duration was significantly shorter in the geometric progression group (496.33+/-54.77 min vs. 421.34+/-63.91 min, P<0.001). There were no differences in the rates of cesarean sections, vaginal deliveries, or uterine hyperstimulation, or in neonatal outcomes. CONCLUSION: A geometric rise in the rate of oxytocin infusion delivery reduced the duration of labor without affecting the rates of cesarean sections and uterine hyperstimulation, or newborn outcomes.     

Misoprostol in labor induction

The efficacy of a new dosing regimen of misoprostol, a recently introduced labor-inducing agent, was studied. Fifty-eight patients received 50 microg of misoprostol intravaginally and the dose was repeated every 3 hours until uterine contractions begin. Those who had an adequate contraction pattern, defined as three contractions in 10 minutes, were not given the repeat dose. Oxytocin augmentation, but not further misoprostol doses, was used in patients with an inadequate contraction pattern. The maximum total daily dose was 200 microg. The patients had the mean age of 28.9 +/- 5.4, the mean gestational age of 211.8 +/- 46.6 days, the mean gravidity of 2.5 +/- 1.2, the mean parity of 0.9 +/- 0.9 and the mean initial Bishop score of 1.6 +/- 1.8. The mean required dose of misoprostol was 120.5 +/- 54.7 microg and 10 of 58 patients required oxytocin augmentation. The mean induction of labor to delivery time was 701.5 +/- 404.0 minutes. When 3 cases who gave birth with caesarean section were excluded, the interval was 708.4 +/- 407.2 minutes. The mean 5th minute Apgar score of the newborns was 8.2 +/- 2.5. Two patients developed tachysystole after the second dose of misoprostol and were managed with vaginal irrigation and O2 supplementation successfully. Slight nausea and vomiting in 2 patients were the other adverse reactions. Our findings revealed that, 50 microg intravaginal misoprostol, combined with oxytocin augmentation when necessary, appears to be an effective and safe method of labor induction.     

Randomized, double-masked comparison of oxytocin dosage in induction and augmentation of labor.

OBJECTIVE: To test the hypothesis that high-dose oxytocin, when used in a masked fashion, would result in shorter labors and less need for cesarean delivery. METHODS: We conducted randomized, double-masked trials of high-dose compared with low-dose oxytocin for augmentation and induction of labor. Patients were randomly assigned to receive oxytocin by either a low-dose protocol (1.5 mU/minute initially, increased by 1.5 mU/minute every 30 minutes) or a high-dose protocol (4.5 mU/minute initially, increased by 4.5 mU/minute every 30 minutes). Oxytocin solutions were prepared by a central pharmacy and infusion volumes (mL/hour) were identical, thus ensuring double masking. RESULTS: A total of 1307 patients were randomized (induction, 816; augmentation, 491). In the group receiving oxytocin for induction, high-dose oxytocin was associated with a significant shortening of labor (oxytocin to complete dilatation: 9.7+/-0.3 compared with 7.8+/-0.2 hours, P<.001; oxytocin to delivery: 10.5+/-0.3 compared with 8.5+/-0.3 hours, P<.001). The cesarean delivery rate with low-dose oxytocin was 15.0%, compared with 11.3% with high-dose oxytocin (P = .17). For nulliparous women undergoing induction, cesarean delivery rates were as follows: Total 17.3% (low dose) compared with 11.7% (high dose), P = .15; cephalopelvic disproportion 11.9% (low dose) compared with 5.9% (high dose), P = .06. When used for augmentation, high-dose oxytocin again was associated with a significant shortening of labor without a significant difference in cesarean birth rates. No differences in neonatal outcomes were noted between the groups for either augmentation or induction. CONCLUSION: When used in a double-masked fashion, high-dose oxytocin is associated with significantly shorter labors without any demonstrable adverse fetal or neonatal effects.     

米索前列醇预防剖宫产术后出血的临床研究

目的观察米索前列醇用于剖宫产预防产后出血的效果。方法选择１８２例剖宫产者,随机分为米索前列醇组、米索前列醇＋催产素组及催产素组。米索前列醇组６０例,术中打开腹膜时口服米索前列醇６００μｇ。米索前列醇＋催产素组６４例,术中打开腹膜时口服米索前列醇６００μｇ,胎儿娩出后宫体肌内注射催产素２０ＩＵ。催产素组５８例,胎儿娩出后宫体肌内注射催产素２０ＩＵ,再静脉滴注催产素２０ＵＩ。以上各组观察术中及术后２小时内出血量。结果术中及术后２小时平均出血量,米索前列醇组为２１２±５６０ｍｌ;米索前列醇＋催产素组为２０８±５５４ｍｌ;催产素组为３４５±６４７ｍｌ。米索前列醇组与催产素组比较,差异有极显著性（Ｐ＜００１）。米索前列醇组与米索前列醇＋催产素组比较,差异无显著性（Ｐ＞００５）。结论米索前列醇促进子宫收缩作用强于催产素,能较好地预防剖宫产术后出血,且用药方便、安全。     

Uterine rupture during induced or augmented labor in gravid women with one prior cesarean delivery.

OBJECTIVE: Our purpose was to examine the risk of uterine rupture during induction or augmentation of labor in gravid women with 1 prior cesarean delivery. STUDY DESIGN: The medical records of all gravid women with history of cesarean delivery who attempted a trial of labor during a 12-year period at a single center were reviewed. The current analysis was limited to women at term with 1 prior cesarean delivery and no other deliveries. The rate of uterine rupture in gravid women within that group undergoing induction was compared with that in spontaneously laboring women. The association of oxytocin induction, oxytocin augmentation, and use of prostaglandin E(2) gel with uterine rupture was determined. Logistic regression analysis was used to examine these associations, with control for confounding factors. RESULTS: Of 2774 women in the analysis, 2214 had spontaneous onset of labor and 560 women had labor induced with oxytocin or prostaglandin E(2) gel. The overall rate of rupture among all patients with induction of labor was 2.3%, in comparison with 0.7% among women with spontaneous labor (P =.001). Among 1072 patients receiving oxytocin augmentation, the rate of uterine rupture was 1.0%, in comparison with 0.4% in nonaugmented, spontaneously laboring patients (P =.1). In a logistic regression model with control for birth weight, use of epidural, duration of labor, maternal age, year of delivery, and years since last birth, induction with oxytocin was associated with a 4.6-fold increased risk of uterine rupture compared with no oxytocin use (95% confidence interval, 1.5-14.1). In that model, augmentation with oxytocin was associated with an odds ratio of 2.3 (95% confidence interval, 0.8-7.0), and use of prostaglandin E(2) gel was associated with an odds ratio of 3.2 (95% confidence interval, 0.9-10.9). These differences were not statistically significant. CONCLUSION: Induction of labor with oxytocin is associated with an increased rate of uterine rupture in gravid women with 1 prior uterine scar in comparison with the rate in spontaneously laboring women. Although the rate of uterine rupture was not statistically increased during oxytocin augmentation, use of oxytocin in such cases should proceed with caution.     

A comparison of orally administered misoprostol to intravenous oxytocin for labor induction in women with favorable cervical examinations

OBJECTIVE: The purpose of this study was to compare orally administered misoprostol with intravenous oxytocin infusion for labor induction in women with favorable cervical examinations (defined as a Bishop score of 6 or more). STUDY DESIGN: One hundred ninety-eight women with indications for labor induction and favorable cervical examinations were assigned randomly to receive oral misoprostol or oxytocin induction. Misoprostol, 100 mg, was administered every 4 hours up to 6 doses, or intravenous oxytocin was administered by standardized protocol. RESULTS: One hundred ten (55.6%) women received misoprostol; 88 (44.4%) received intravenous oxytocin. There was no statistically significant difference in the average interval from start of induction to vaginal delivery, being longer in the misoprostol group (789.4 +/- 510.2 minutes) than in the oxytocin group (654.0 +/- 338.2 minutes, P=.19, log-transformed data). Two women had tachysystole develop in each treatment group. More women in the misoprostol group experienced hyperstimulation (7/110, 6.4%) than in the oxytocin group (0/88, P=.02, Fisher exact test). Nine (8.1%) misoprostol-treated women and 8 (9.1%) oxytocin-treated women underwent cesarean deliveries (P=.82). There was a presumed uterine rupture in a misoprostol-treated multipara women. There were no statistically significant differences in neonatal outcomes between the groups. CONCLUSION: Oral misoprostol offers no benefit over intravenous oxytocin for labor induction in women with favorable cervical examinations. It is associated with a higher likelihood of uterine hyperstimulation and may increase the risk of uterine rupture.     

Oral, vaginal and sublingual misoprostol for induction of labor.

OBJECTIVE: To evaluate the effectiveness and safety of different administration routes of misoprostol for induction of labor. METHOD: PubMed, Cochrane Library and EMBASE searches were carried out using the keywords oral, vaginal, sublingual, buccal, misoprostol, labor induction, identifying randomized case-controlled trials comparing different routes for giving misoprostol to induce labor, published in English between 1994 and 2004. RESULTS: Seventeen studies (3549 participants) were included. Compared to vaginal administration, oral misoprostol was associated with higher failure rates for achieving vaginal delivery within 24 h (odds ratio (OR) 1.61, 95% confidence interval (CI) 1.23-2.10), higher rates of uterine hyperstimulation without fetal heart rate (FHR) changes (OR 2.21, 95% CI 1.12-4.34) and lower cesarean section rates (OR 0.74, 95% CI 0.56-0.97). A lower dose of oral misoprostol (50 microg) compared to the 25-50 microg administered vaginally was associated with a higher rate of vaginal delivery not being achieved within 24 h (OR 3.60, 95% CI 2.10-6.18), more need for oxytocin augmentation (OR 2.19, 95% CI 1.65-2.92), less uterine hyperstimulation both without FHR changes (OR 0.58, 95% CI 0.42-0.80) and with FHR changes (OR 0.34, 95% CI 0.17-0.67) and fewer cesarean sections (OR 0.69, 95% CI 0.51-0.91). Compared to vaginal administration, buccal misoprostol resulted in a higher rate of failure to achieve vaginal delivery after 24 h, more frequent uterine hyperstimulation and lower rates of cesarean section, but these differences were not significant. When 50 mug of misoprostol used sublingually was compared to oral administration, the sublingual misoprostol was associated with less failure to achieve vaginal delivery after 24 h, less oxytocin augmentation and reduced cesarean section, but none of the differences were statistically significant. CONCLUSIONS: Vaginal misoprostol appears more effective than the equivalent dosage administered orally. However, the vaginal route appears to be associated with a higher risk of uterine hyperstimulation. Sublingual misoprostol seems an effective route of administration, but a lack of data necessitates more clinical trials to establish the effectiveness and safety of the buccal/sublingual route.     

Use of magnesium sulfate to treat hyperstimulation in term labor

Magnesium sulfate has been shown in vivo and in vitro to decrease the frequency of uterine contractions while maintaining the amplitude; we therefore decided to assess the use of magnesium sulfate infusion in cases of uterine hyperstimulation. The medical records were reviewed retrospectively for 37 term pregnant patients diagnosed as having uterine hyperstimulation during labor. None of them had medical or obstetric complications. Twenty-two of them received oxytocin augmentation for abnormal labor. Although the vast majority of these patients had a decrease of the hyperstimulation while being given the magnesium, 31.8% in the group receiving oxytocin alone (P less than .05). Fifteen additional patients received magnesium sulfate for uterine hyperstimulation although they were not receiving oxytocin; of these, 16.7% required cesarean delivery. This rate was no different from that of the patients who required labor augmentation, but was double the overall primary cesarean rate at our hospital. There appears to be a group of patients with abnormal uterine activity (either spontaneous or associated with oxytocin augmentation) that responds to treatment with magnesium sulfate.     

Outpatient misoprostol compared with dinoprostone gel for preinduction cervical ripening: a randomized controlled trial

OBJECTIVE: To determine whether a single outpatient dose of intravaginal misoprostol (versus intracervical dinoprostone gel) reduces the oxytocin use for induction. Despite the numerous trials examining misoprostol for induction, the efficacy of a single outpatient dose of misoprostol followed by oxytocin induction is unknown. METHODS: Patients with a term, vertex, singleton pregnancy and a Bishop score of 6 or less were randomly assigned to receive misoprostol (n = 42, 0.25 microg intravaginally) or dinoprostone gel (n = 42, 0.5 mg intracervically) the evening before oxytocin induction. Patients were monitored for 3 hours after administration and discharged to home if fetal assessment was reassuring, for readmission the next morning for oxytocin. Primary outcomes were oxytocin dose, time, and dose intensity (dose divided by duration). Secondary outcomes were incidence of labor, uterine hyperstimulation, cesarean delivery, Apgar score. Statistics used were chi(2), Student t test, Mann-Whitney rank sum test, and Fisher exact test. P < .05 was accepted as statistically significant. RESULTS: A single dose of misoprostol significantly decreased the cumulative dose of oxytocin, the cumulative time of oxytocin administration, and the dose intensity of oxytocin (dose divided by time). Data are as follows (mean +/- standard error of the mean): oxytocin dose-dinoprostone 10,929 +/- 219 mU, misoprostol 6,081 +/- 170 mU, P = .008; oxytocin time-dinoprostone 798 +/- 11 minutes, misoprostol 531 +/- 11 minutes, P = .009; dose intensity-dinoprostone 11.3 +/- 0.1 mU/min, misoprostol 7.4 +/- 0.2 mU/min, P = .003. Misoprostol induced labor during the ripening period in 19 of 41 of patients, compared with 6 of 42 after dinoprostone (P = .002). There was no difference in cesarean delivery (dinoprostone, 8/42; misoprostol, 9/42; P = 1.00). There was no difference in short-term neonatal outcome. No patient had hyperstimulation or required cesarean delivery for nonreassuring fetal assessment during the ripening period. CONCLUSION: A single dose of misoprostol administered in the outpatient setting significantly decreases oxytocin use, largely due to labor within the ripening period.     

Oxytocin dose and the risk of uterine rupture in trial of labor after cesarean

OBJECTIVE: To examine the association between uterine rupture and oxytocin use in trial of labor after cesarean. METHODS: A case-control study was performed. Cases were all women with uterine ruptures who received oxytocin during a trial of labor after a single cesarean delivery within a 12-year period (n = 24). Four controls undergoing trial of labor after a single cesarean delivery were matched to each case by 500 g birth weight category, year of birth, and by induction or augmentation (n = 96). The study had an 80% power to detect a 40% increase in oxytocin duration or a 65% increase in total oxytocin dose. RESULTS: No significant differences were seen in initial oxytocin dose, maximum dose, or time to maximum dose. Although women with uterine ruptures had higher exposure to oxytocin as measured by mean total oxytocin dose (544 mU higher) and oxytocin duration (54 minutes longer), these differences were not statistically significant. Women with uterine rupture who received oxytocin were more likely to have experienced an episode of uterine hyperstimulation (37.5% compared with 20.8%, P =.05). However, the positive predictive value of hyperstimulation for uterine rupture was only 2.8%. CONCLUSION: Although no significant differences in exposure to oxytocin were detected between cases of uterine rupture and controls, the rarity of uterine rupture limited our power to detect small differences in exposure. In women receiving oxytocin, uterine rupture is associated with an increase in uterine hyperstimulation, but the clinical value of hyperstimulation for predicting uterine rupture is limited.     

Oral misoprostol vs. intravenous oxytocin in reducing blood loss after emergency cesarean delivery.

OBJECTIVE: To compare the effectiveness of oral misoprostol and intravenous oxytocin in reducing blood loss in women undergoing indicated or elective cesarean delivery (CD) under spinal anesthesia. METHODS: In this prospective, double-blind pilot study, 56 parturients who received 5 IU of intravenous oxytocin after cord clamping were randomized to further receive either misoprostol orally and a placebo infusion intravenously or placebo orally and an oxytocin infusion intravenously. RESULTS: After adjustment was made for the sonographically estimated amniotic fluid volume, there was no statistical difference in blood loss between the 2 groups (mean+/-S.D., 1083+/-920 mL in the oxytocin group vs. 970+/-560 mL in the misoprostol group; P=.59). CONCLUSION: Oxytocin followed by oral misoprostol is as effective as an oxytocin injection followed by an oxytocin infusion in reducing postoperative blood loss after CD, and the protocol may be a safe, valuable, and cost-effective alternative to oxytocin alone. Visual estimation of intraoperative blood loss undervalues the effective value of misoprostol use by 30%.     

Uterine contraction pressures with oxytocin induction/augmentation

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

Pulsatile oxytocin for induction of labor: a randomized prospective controlled study

In a prospective randomized study, 20 patients with term pregnancies underwent induction of labor with either continuous or pulsed (every 8 minutes) intravenous oxytocin infusion. There were no significant differences with respect to induction-labor interval, induction-delivery interval, cesarean section rates, need for pain relief and Apgar scores. Sixty percent of patients receiving continuous oxytocin infusion developed uterine hyperstimulation but only 10% receiving pulsed oxytocin did so. However, the difference was not significant. The mean +/- SEM total amount of oxytocin given by continuous infusion was 4237 +/- 1066 mU which was 70% more than by pulsatile infusion (2454 +/- 808 mU). The highest rate of oxytocin infused was significantly lower by pulsatile administration (5.2 +/- 0.8 mU/min) than by continuous infusion (9.2 +/- 1.8 mU/min, p = less than 0.05). Our study demonstrates that pulsed administration of oxytocin every 8 minutes is as effective and safe as continuous intravenous infusion of oxytocin for induction of labor, requires less oxytocin with therefore, a wider margin of safety and is consistent with the pulsatile release of oxytocin during normal labor.     

Induction of labor with 50 and 100 microg of misoprostol: comparison of maternal and fetal outcomes

OBJECTIVE: The aim of this randomized controlled study was to compare the efficacy and the safety of different regimens of misoprostol for labor induction. MATERIALS AND METHODS Eligible women received intravaginal 100 microg, every 6 h or 50 microg every 4 h. Treatment continued until: (1) dilatation >3 cm; (2) rupture of membranes (artificial); (3) signs of uterine hyperstimulation; (4) adequate contraction pattern (three contraction/10 min). Managing clinician might use oxytocin during labor. Cesarean section rate was the main outcome that was considered variably. Other outcome measures were neonatal outcome (Apgar scores, meconium staining, and umbilical artery pH) and induction to delivery interval. RESULTS: A total number of 72 women received either misoprostol 100 microg (n=37), or 50 microg (n=35) randomly. The two groups had similar mean Bishops scores at induction (4.10+/-2.4 versus 4.2+/-2.1; P=0.85), rates of nulliparity, use of epidural anesthesia, and oxytocin augmentation. In two groups the number of doses of misoprostol used was similar (1.6+/-0.5 versus 1.7+/-0.3) CONCLUSION: There was not any difference between the two groups in the mean+/-S.D. time to delivery (h) and cesarean rate. Likewise, there was not a significance between two groups in the rates of 5 min Apgar score, and of meconium passage.     

Rate of uterine rupture during a trial of labor in women with one or two prior cesarean deliveries.

OBJECTIVE: We sought to determine whether there is a difference in the rate of symptomatic uterine rupture after a trial of labor in women who have had 1 versus 2 prior cesarean deliveries. STUDY DESIGN: The medical records of all women with a history of either 1 or 2 prior cesarean deliveries who elected to undergo a trial of labor during a 12-year period (July 1984-June 1996) at the Brigham and Women's Hospital were reviewed. Rates of uterine rupture were compared for these 2 groups. Potential confounding variables were controlled by using logistic regression analyses. RESULTS: Women with 1 prior cesarean delivery (n = 3757) had a rate of uterine rupture of 0.8%, whereas women with 2 prior cesarean deliveries (n = 134) had a rate of uterine rupture of 3.7% (P =.001). In a logistic regression analysis that was controlled for maternal age, use of epidural analgesia, oxytocin induction, oxytocin augmentation, the use of prostaglandin E(2) gel, birth weight, gestational age, type of prior hysterotomy, year of trial of labor, and prior vaginal delivery, the odds ratio for uterine rupture in those patients with 2 prior cesarean deliveries was 4.8 (95% confidence interval, 1.8-13. 2) CONCLUSIONS: Women with a history of 2 prior cesarean deliveries have an almost 5-fold greater risk of uterine rupture than those with only 1 prior cesarean delivery.     

Pulsatile administration enhances the effect and reduces the dose of oxytocin required for induction of labor

Pulsatile administration of oxytocin was compared with continuous infusion of oxytocin for induction of labor in pregnant rats. The dosages consisted of intravenous injections of 0, 2.5, and 5 mU oxytocin every 10 minutes and intravenous infusion of 1 mU/minute of oxytocin in 0.9% sodium chloride. These doses are within the range of endogenously secreted pulses. All treatments began on day 22 at 2 p.m. and continued for 8 hours. Pulsatile administration resulted in a marked reduction in the dose of oxytocin required to induce labor. Using 5 mU pulses, birth was induced with 18.4%, and using 2.5 mU pulses, with 24% of the dose needed using continuous infusion. Parturition was advanced by 12 hours on the average by oxytocin treatment, but no significant differences were observed between the various oxytocin dosage regimens in this regard or in regard to gestation length, induction-delivery interval, duration of delivery, or the proportion of living or dead pups. Significantly more uterine activity was induced with each mU of oxytocin using pulsatile administration than using continuous infusion. There was no evidence for down-regulation of oxytocin receptors during a continuous infusion of oxytocin. We postulate that the greater efficacy of oxytocin pulses to induce uterine activity and delivery in comparison to continuous infusions is due to a more effective stimulation of prostaglandin F2 alpha release from the decidua. The amount of oxytocin needed for induction of labor with 2.5 mU pulses was similar to the decrease in neurohypophyseal oxytocin content during the first stage of spontaneous labor, and uterine activity elicited was also similar to that observed during spontaneous labor.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of vaginal pH on the efficacy of vaginal misoprostol for induction of labor

BACKGROUND: Misoprostol was reported to be an effective agent for cervical ripening and induction of labor. Our purpose was to evaluate whether vaginal pH affected the efficacy of misoprostol for induction of labor. METHODS: The vaginal pH of 103 women admitted for induction of labor were measured. According to the vaginal pH, two groups were generated, those with a vaginal pH <5 (n= 65), and those with a vaginal pH > or =5 (n=38). All women received intravaginal misoprostol tablets, 50 microg every 4 hours up to three doses. Further medication was not given after entry into active labor or spontaneous rupture of membranes. In cases of failed induction or arrest disorders oxytocin augmentation was used. RESULTS: The average interval from start of induction to vaginal delivery was shorter, and oxytocin augmentation was required less commonly in the lower pH group. We did not find any significant difference in cesarean section rates, or incidence of adverse maternal or fetal outcome. CONCLUSION: Vaginal pH may affect the pharmacokinetics of vaginally administered misoprostol, and may cause an alteration in induction to delivery interval.