Frequency Of Uterine Contractions Research Articles

Mock embryo transfer does not affect uterine contractility

To assess the degree of utero-stimulation induced by transcervical introduction of a catheter as in mock ET. Prospective study. Reproductive medicine unit. Eighty volunteers undergoing mild ovarian stimulation and IUI. Just before IUI, women had uterine contraction (UC) frequency assessed with 2-minute sagittal ultrasound scans of the uterus (precatheter measurement). Thereafter, one of three types of catheters, each with a different stiffness level (low, n = 25; medium, n = 30; or high, n = 25) was introduced into the cervix up to the inner cervical os, then immediately withdrawn, and the UC frequency reassessed (postcatheter measurement). Percentage change in UC frequency. Median (range) UC frequency was not significantly different at pre- and postcatheter measurements: 2.0 (0.0-4.5) UC per minute and 2.2 (0.0-5.5) UC per minute. In addition, the stiffness of the catheter (low, medium, or high) did not influence the UC frequency, with median (range) percentage of change from pre- to postcatheter measurement at 0 (-100% to +75%), 0 (-100% to +100%), and 0 (-40% to +100%), respectively. The introduction of a catheter up to the inner cervical os, as usually performed in mock ET, does not stimulate uterine contraction frequency, irrespective of catheter stiffness.

The effects of etomidate on the contraction of pregnant rat uterine smooth muscle.

It has been reported that etomidate has the relaxant effects on vascular, tracheal, and non-pregnant uterine smooth muscle in vitro. The purpose of this study was to investigate the relaxant effects of etomidate on the contraction of the pregnant rat uterine smooth muscle. Uterine muscle tissues were obtained from pregnant rats (n = 15). The uterine segments were mounted in organ baths filled with Krebs solution. After oxytocin-induced contractile activity had been established, etomidate in incremental concentrations (10(-7) to 10(-3) M) was added cumulatively to the bath, each administered 20 min apart, and resultant changes in contractile activity were continuously recorded. EC5 (effective concentration of 5% reduction), EC25, EC50, EC75, and EC95 on active tension were calculated using a probit model. Etomidate (10(-7) to 10(-3) M) induced dose-dependent decreases in amplitude and frequency of uterine contraction. The EC50 of etomidate on active tension were 5.91 x 10(-5) M. These results demonstrate that etomidate had inhibitory effects on pregnant rat uterine muscle at supraclinical concentration (5.91 x 10(-5) M).

Acidemia at Birth, Related to Obstetric Characteristics and to Oxytocin Use, During the Last Two Hours of Labor

During the active phase of the second stage of labor, with maternal expulsive efforts, there is a decline in fetal pH values and an increase in lactic acid concentrations. Little information is available on the association between the occurrence of acidemia at birth and oxytocin use during the second stage of labor. This case-control study compares uterine contraction frequency, oxytocin use, and other obstetric parameters during the last 2 hours of labor in neonates with acidemia (umbilical artery pH <7.05) and without acidemia (cord artery pH ≥7.05) at birth. Cardiotocography tracings were recorded in a blinded fashion. A hyperactive contraction pattern was defined as 6 or more contractions/10 minutes. A total of 304 neonates with acidemia were identified among 28,486 singleton newborns ≥34-weeks’ gestational age delivered at 2 university hospitals in Sweden between 1994 and 2004. Baseline neonatal and obstetric characteristics were similar in the cases and controls. Oxytocin administration during the last 2 hours of labor was more common in cases compared with controls (61.2% vs. 41.7%, P < 0.001). Risk factors associated with acidemia at birth in univariate analysis were ≥6 contractions/10 minutes [odds ratio (OR) 4.94 with a 95% confidence interval (CI) of 3.25–7.49, P < 0.001]; oxytocin use (OR 2.20 with a 95% CI of 1.66–2.92, P < 0.001); bearing down ≥45 minutes (OR 1.77 with a 95% CI of 1.31–2.38, P < 0.001); and occipito-posterior position (OR 2.18 with a 95% CI of 1.19–3.98, P < 0.01). Multivariate logistic regression analysis showed that only ≥6 contractions/10 minutes (OR 5.36 with a 95% CI of 3.32–8.65) and oxytocin use (OR 1.89 with a 95% CI of 1.21–2.97) were independent risk factors for acidemia. Of the cases with hyperactive labor, 75% had received oxytocin. Cardiotocography patterns were abnormal in 68.8% of cases and in 26.1% of controls (P < 0.001). These findings are consistent with previous reports showing an association between hyperactive uterine contraction patterns and fetal acidemia. The investigators believe that this is the first study to demonstrate that oxytocin use is a risk factor for acidemia after adjustment for the influence of uterine contraction frequency.

Maternal obesity, uterine activity, and the risk of spontaneous preterm birth.

To assess the associations among maternal obesity, uterine contraction frequency, and spontaneous preterm birth in women at risk for spontaneous preterm birth. In a secondary analysis, we analyzed data from 253 women at risk for spontaneous preterm birth (prior spontaneous preterm birth, vaginal bleeding) enrolled in a multicenter observational study of home uterine activity monitoring at 11 centers. All women wore a uterine activity monitor twice daily from 22 weeks through 34 weeks of gestation. Mean and maximal contractions/hour at 22-24, 25-26, 27-28, 29-30, 31-32 weeks, and at or after 33 weeks of gestation were compared between overweight/obese women (a body mass index [BMI] at 22-24 weeks greater than 25 kg/m) and normal/underweight women (a BMI of 25 kg/m or less) at each gestational age interval. Multivariable analysis evaluated the influences of BMI, contractions, fetal fibronectin, and transvaginal cervical length on spontaneous preterm birth before 35 weeks. Obese/overweight women (n=156) were significantly less likely to experience spontaneous preterm birth before 35 weeks (8.3% compared with 21.7%, P<.01). For each gestational age interval before 32 weeks, obese/overweight women had fewer mean contractions/hour (P<.01 for each) and maximal contractions/hour (P<.01 for each) than normal/underweight women, although their mean cervical lengths (34.3 mm compared with 33.1 mm, P=.25), and fetal fibronectin levels (7.1% compared with 7.2% 50 ng/mL or more, P=.97) were similar at study enrollment. Obese/overweight status was associated with a lower risk of spontaneous preterm birth before 35 weeks after controlling for contraction frequency and other factors evaluated at 22-24 weeks, but not at later periods. Obese/overweight women at risk for spontaneous preterm birth exhibit less uterine activity and less frequent spontaneous preterm birth before 35 weeks of gestation than normal/underweight women. II.

Acidemia at birth, related to obstetric characteristics and to oxytocin use, during the last two hours of labor

Evaluate obstetric characteristics during the last two hours of labor in neonates born with acidemia. Case-control study. Delivery units at two university hospitals in Sweden. Out of 28,486 deliveries during 1994-2004, 305 neonates had an umbilical artery pH value <7.05 at birth. neonates with an umbilical artery pH < 7.05. Controls were neonates with pH > or = 7.05 and an Apgar score > or =7 at 5 minutes. Obstetric characteristics, cardiotocographic patterns and oxytocin treatment during the last two hours of labor were recorded. In the univariate analysis, > or =6 contractions/10 minutes (odds ratio (OR) 4.94, 95% confidence interval (CI) 3.25-7.49), oxytocin use (OR 2.20, 95% CI 1.66-2.92), bearing down > or =45 minutes (OR 1.77, 95% CI 1.31-2.38) and occipito-posterior position (OR 2.18, 95% CI 1.19-3.98) were associated with acidemia at birth. In the multivariate analysis, only > or =6 contractions/10 minutes (OR 5.36, 95% CI 3.32-8.65) and oxytocin use (OR 1.89, 95% CI 1.21-2.97) were associated with acidemia at birth. Among cases with > or =6 contractions/10 minutes, 75% had been treated with oxytocin. Pathological cardiotocographic patterns occurred in 68.8% of cases and in 26.1% of controls (p<0.001). A hyperactive uterine contraction pattern and oxytocin use are the most important risk factors for acidemia at birth. The increased uterine activity was related to overstimulation in the majority of cases. The duration of bearing down is less important when uterine contraction frequency has been considered.

Uterine Contractions Depend on KIT-Positive Interstitial Cells in the Mouse: Genetic and Pharmacological Evidence

In the gastrointestinal tract, interstitial cells of Cajal (ICCs) generate a pacemaker activity. They produce electric slow waves that trigger and coordinate gut smooth muscle contractions. Interstitial cells of Cajal's slender shape is revealed by KIT immunostaining. Based on several features, including KIT expression and KIT dependence, ICC-like cells were identified in nongastrointestinal tissues. Here, we investigated in the mouse whether uterine contractions depend on ICC-like cells' activity. By labeling KIT-expressing cells, we found putative ICC-like cells in the uterus, observed as KIT-positive interstitial, long spindle-shaped cells with fine branched cytoplasm processes, distributed in muscular layers and in subepithelial connective tissue. We then checked the potential KIT dependence of ex vivo contractile activity of the uterus by combining genetic and pharmacological approaches, using the Kit W-v hypomorphic mutation, and imatinib as a KIT noncompetitive inhibitor. We found a significant reduction in frequency of longitudinal uterine contractions in Kit W-v/Kit W-v compared with Kit+/+ mice, whereas amplitude was unaffected. There was no difference in frequency or amplitude of circular uterine contractions between Kit W-v/Kit W-v and Kit+/+ mice. Ex vivo treatment of Kit+/+ uterine horns with imatinib resulted in a dose-dependent reduction of the frequency and amplitude of longitudinal myometrial contractions. Amplitude and frequency of circular contractions were unaffected in presence of imatinib. These concurrent results suggest that longitudinal contractions of the uterus depend on a KIT signaling pathway of ICC-like cells. The existence of ICC-like cells in the myometrium may enhance our understanding of uterine spontaneous contractile activity and suggest new approaches for treatment of uterine contractility disorders.

Antepartum uterine contraction patterns in twin pregnancies with and without preterm labor and delivering before or after 36 weeks

The purpose of this study was to identify differences in antepartum uterine contraction frequency (UCF) in twin pregnancies with and without preterm labor (PTL). Twin gestations enrolled for outpatient surveillance with twice daily electronic uterine activity monitoring and telephonic nursing assessment, without interventional delivery were identified. Mean UCF for each gestational week was compared between women without PTL or preterm delivery (PTD) < 36 weeks (controls) and those with a PTL diagnosis delivering at < 36 weeks (PTL/PTD group), and those with PTL with delivery > or = 36 weeks (PTL/GAD > or = 36 group). Data from 7891 patients with 267,840 monitored hours were analyzed. UCF at each gestational week was significantly higher for patients experiencing PTL with or without PTD compared to control. UCF was similar for patients with PTL with or without PTD < 36. Twin pregnancies complicated with PTL have a higher UCF than those that do not experience PTL. Outpatient surveillance may be beneficial in this population.

Sperm distribution in the oviduct and uterus of mares within two hours after artificial insemination

Spermatozoa are deposited directly into the uterus of the mare during mating or artificial insemination (AI). Frequent uterine contractions after AI carry sperm back and forth between the uterine body and the horn tips (Katila et al. 2000). It is very likely that some of these sperm gain access to the oviducts very soon after AI, but the time of the first appearance of sperm in the oviducts of the mare has not been documented. Within 1 h after breeding, seminal compounds were found in the oviduct of the mare (Mann et al. 1956) and sperm were detected in the oviducts 2 h after insemination with fresh or frozen-thawed semen (Bader 1982). Large numbers of sperms were present in the oviducts 4 h after insemination, but there was a reduction in the number of sperms recovered from the oviducts 6 h after insemination (Bader and Krause 1980). These observations suggest a gradual elimination of sperms from the oviduct and the cessation of further sperm transport through the uterus (Bader 1982). Pregnancy rates were significantly lowered when mares were flushed within 2 h after AI, but uterine lavage performed at 4 h had no adverse effect on fertility (Brinsko et al. 1990 and 1991).

Successful continuation of pregnancy after repair of a midgestational uterine rupture with the use of a fibrin-coated collagen fleece (TachoComb) in a primigravid woman with no known risk factors

We report the first case of successful continuation of pregnancy after repair of a midgestational uterine rupture with the use of a fibrin-coated collagen fleece (TachoComb, Nycomed, Linz, Austria). For midgestational uterine rupture, adequate uterine repair and close surveillance of preterm labor could improve perinatal outcome by permitting continuation of the pregnancy.

Mechanisms behind intrauterine device-induced luteal persistence in mares

Intrauterine glass balls are used to prevent oestrous signs in sports mares, but the mechanism of action is unknown. It has been suggested that the glass ball can mimic an embryo or act via an induced chronic uterine inflammation and absent or continuous low-grade prostaglandin (PG) release. The purpose of this study was to induce prolonged luteal function in mares using a small intrauterine device (IUD) and to study the mechanisms behind prolonged IUD-induced luteal function. A uterine swab and a biopsy specimen were obtained in early oestrus. A water-filled plastic ball, diameter 20 mm and weight 3.6 g, was inserted into the uterus 2–4 days after ovulation; the control mares underwent similar cervical manipulation without ball insertion. The mares were examined three times per week until day 23 and twice weekly thereafter until they returned to oestrus (transrectal palpation, ultrasonography and progesterone determination). The location of the IUD was recorded and ultrasound scans were video-recorded to assess the frequency of uterine contractions. When the mare returned to oestrus, a uterine swab and biopsy specimen were obtained and the bacteriological, cytological and histological (inflammation and glandular dilation) results compared with the samples obtained before the IUD insertion. The PG F 2α metabolite levels were measured in the plasma of four control mares and eight IUD mares on days 11–16. The IUD induced a prolonged luteal phase in 75% of the mares (9/12; IUD-P); the mean dioestrous length was 57.0 days. The three mares that did not respond to the IUD (IUD-N) showed a mean dioestrous length of 15.7 days and the 12 control mares 16.1 days. The inflammation and glandular dilation scores were not significantly different in pre- and post-manipulation biopsy specimens. Although locational changes of the IUD were observed, they occurred over very small distances and were mostly limited within the body-bifurcation area. The IUD-N and control mares showed increased uterine contractility 11–16 days post-ovulation, whereas the IUD-P mares did not. The control mares ( n = 4) and IUD-N mares ( n = 2) showed increased PG levels from day 14 post-ovulation, while the IUD-P mares ( n = 6) showed basal levels only. We concluded that the IUD did not cause continuous PG release and suggest that close contact of the IUD with the endometrium may prevent the endometrial cells from releasing PGF 2α.

Assessment of myoelectrical signal parameters in estrogen, progesterone, and human chorionic gonadotropin administered in nonpregnant rat myometrium after ovariectomy

To investigate the correlation of myoelectrical signals with spontaneous contractile events and physiological states in the nonisolated uterine horn of rats. In vivo uterine myoelectrical activity recording study. Animal and pharmacology laboratory at Inonu University. Thirty-six female Wistar albino rats. Six animals were not castrated and served as a sham-operated control group; the other 30 were ovariectomized (OVX) and put into groups: unbiased OVX subjects, estrogen (E)-biased OVX subjects, P-biased OVX subjects, E-plus-P-biased OVX subjects, and hCG-biased OVX subjects. An MP100 A-CE was used for data acquisition, and a personal computer was used for processing. Besides the temporal, spectral, and joint time-frequency (spectrotemporal) analysis, some quantitative measures such as standard deviation and mark to space power ratios of myoelectrical signals were measured. Progesterone, E, and hCG administration down-regulated the power and contraction frequency of the uterine electrical signal. The spectral concentrations that occurred around the 0.9, 0.35, and 0.7 Hz frequency ranges may be distinguishing characteristics for P, E, and hCG, respectively. Based on the obtained results, uterine contractions change with ovariectomy and administration of hormones. Progesterone, E, and hCG particularly prolong the quiescent periods of the uterus by reducing the frequency of uterine contractions as well as the power of the myoelectrical activity. Individual or combined use of P, E, or hCG might favor quiescence of the uterine muscle and the maintenance of pregnancy.

A prospective masked observational study of uterine contraction frequency in twins

This study was undertaken to compare uterine contraction frequency in twins versus singletons and to determine if contraction frequency can be an efficient predictor of spontaneous preterm birth in twin gestations. Fifty-nine twin and 306 singleton gestations were enrolled between 22 and 24 weeks at 11 centers. Contraction frequency was recorded with a home uterine activity monitor (HUAM) 2 or more times per day on 2 or more days per week until delivery or 36-6/7 weeks. Masked HUAM data were interpreted according to standard protocol. Repeated measures analyses were used to determine whether mean or maximum uterine contraction frequency per hour differed between singleton and twin gestations across gestational age, by time of day, and by delivery before 35 weeks or beyond. Uterine contraction frequency was also evaluated by logistic regression and receiver operator characteristic (ROC) curves as tests to predict spontaneous preterm birth. There were 34,908 hours of HUAM data recorded by the 306 singleton gestations and 5,427 hours by the 59 women with twins. Uterine contraction frequency was significantly greater in twins (P = .002) compared with singletons, regardless of gestational age. Contraction frequency in twins increased significantly with gestational age and time of day (1600-0359 hours); but was not associated with spontaneous preterm birth. Maximum uterine contraction frequency was associated with preterm birth less than 35 weeks but only in the morning (am) recording (0400-1559) and at the 29- to 30-week gestational age interval. This relationship was modest (odds ratio 1-2) and not consistent across gestational age or between the am and afternoon/evening (pm) monitoring sessions. ROC analysis revealed no contraction frequency that efficiently identified twins who delivered prematurely at any 2-week gestational age interval. Mean uterine contraction frequency was significantly higher for twin gestations than singletons throughout the latter half of pregnancy and between 1600 and 0359 hours but was not higher among twins who delivered less than 35 weeks' gestation. Neither maximum am or pm contraction frequency predicted spontaneous preterm birth less than 35 weeks' gestation in twin pregnancies.

The effect of continuous morphine administration on maternal plasma oxytocin concentration and uterine contractions after open fetal surgery

Objective. A major complication of open fetal surgery is prematurity. We propose that fetal and maternal stress/pain after surgery may affect the concentration of circulating oxytocin and the frequency of uterine contractions, thus increasing the risk of preterm delivery. The objective of this study was to test whether continuous morphine sulfate administration after open fetal surgery has an effect on maternal plasma oxytocin concentration and the frequency of uterine contractions.Methods. An established time-pregnant primate model for open fetal surgery was used. From the time of surgery until the end of the three-day study period, three animals received prophylactic antibiotics, a bolus of indomethacin, and a bolus of morphine sulfate (group I). Three other animals received the same prophylactic antibiotics and an i.v. bolus of indomethacin, as well as a continuous i.v. infusion of morphine sulfate throughout the entire study period (group II). Maternal blood samples were collected to determine oxytocin plasma concentrations. Oxytocin was measured by radioimmunoassay. Uterine activity was continuously recorded through an amniotic fluid catheter and quantified as number of contractions (⩾10 mmHg increase from base line in intrauterine pressure) per hour (UCs/h).Results. The mean maternal plasma oxytocin concentration was higher (p < 0.01) and the number of uterine contractions more frequent (p < 0.05) in the group of animals with intermittent doses of morphine than in the group that received morphine continuously.Conclusions. These data suggest that maternal plasma oxytocin concentration and uterine activity after open fetal surgery may be related to inadequate maternal/fetal analgesia/sedation.

Possible neural mediation of the central effects of oxytocin on uterine motility

The central nervous system contains the nuclei at the origin of autonomic and neuroendocrine pathways to the uterus. Although the anatomical basis of these pathways is known, the conditions of their recruitment and their interactions in the context of copulation remain to be explored. We tested the hypothesis that some central mechanisms could simultaneously recruit both pathways to the uterus. In this aim, we recorded intrauterine pressure changes in anesthetized female rats at the estrus stage after intracerebroventricular (ICV) administration of oxytocin (OT). Doses of 0.3-300 ng elicited increases of frequency and amplitude of uterine contractions. These effects were partly mimicked by the OT agonist [Thr(4),Gly(7)]OT but not by arginine vasopressin. They were blocked by the OT receptor antagonist atosiban delivered either ICV or intravenously. The latter suggests that ICV OT activated the systemic release of OT. The effects of OT were also blocked by hexamethonium, a ganglionic blocking agent, by atropine, a muscarinic receptor antagonist, and by N(omega)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis. The results reveal that ICV OT recruits autonomic efferent pathways to the uterus. These results support our hypothesis that the activation of central nuclei can promote uterine contractility, and that OT may be a central coordinator of autonomic and neuroendocrine pathways. The hypothalamus, the source of direct OT-ergic projections to the pituitary, the brain stem, and the spinal cord, may be a target of central OT.

Blastocyst transfer, its risk of Ectopic Pregnancy in Assisted Reproduction

ABSTRACT The clinical benefit of Blasotcyst transfer (BT) in IVF-ET is still controversial. Recent study elucidated the benefit of BT to reduce ectopic pregnancy in assisted reproduction. Retrospective analysis of pregnancies with BT showed lower ectopic pregnancy rate compared to the cleaved stage transfer, especially among patients with tubal factor. There could be few chance of embryo migration into the tube after BT because of a limited period from transfer to implantation, and a reduced frequency of uterine contraction at the time of transfer.

Effects of (artificial) boar stimuli on uterine activity in estrous sows

This study aims to examine influences of specific boar stimuli on uterine activity in estrous sows, by comparing uterine activity in presence of a mature teaser boar and a robot boar with variable stimuli. Nineteen multiparous, cyclic, commercial crossbred sows were used. Intra-luminal uterine pressure was measured using a non-surgical method for 45 min before applying one of four treatments in combination with a back-pressure-test (BPT): (1) robot with olfactory and auditory stimuli (R + O + A) ( n = 16), (2) robot with auditory stimuli (R + A) ( n = 16), (3) robot without additional stimuli (R) ( n = 16), (4) a mature boar (boar) ( n = 15). After treatment, measurements continued for 30 min. For each measurement, frequency, mean amplitude and mean duration of uterine contractions were determined. Spontaneous frequency of uterine contractions was 18.6 ± 0.7 h −1 on average and did not differ between treatments. Frequency of contractions increased significantly for the boar (+5.6 ± 1.3 h −1; P < 0.01), R + O + A (+3.9 ± 1.3; P < 0.01) and R + A (+2.6 ± 1.3; P < 0.05). The effect of boar presence on frequency of contractions was greater than the effect of R ( P < 0.05). Amplitude and duration of contractions were not affected by treatment. The change in frequency was dependent on spontaneous frequency ( P < 0.01). In conclusion, the higher the level of boar stimuli, the greater the increase in frequency of uterine contractions. The results indicate that the used combinations of artificial boar stimuli do not mimic a ‘whole’ boar. It is unclear which boar stimuli stimulate maximal uterine activity during estrus.

Nitroglycerin to Facilitate Insertion of a Labor Epidural

Stanford University School of Medicine, Stanford, California. bcarvalho@stanford.eduPlacement of a labor epidural or combined spinal–epidural in advanced labor is technically challenging. Regular painful contractions often make it difficult for the parturient to remain still during epidural placement, and this may increase the chance of an accidental dural tap or nerve injury. Decreasing the intensity and frequency of uterine contractions during neuraxial placement in this setting may be advantageous. Previous reports show that nitroglycerin produces rapid effective uterine relaxation.1–5Nitroglycerin to facilitate the placement of a labor epidural has not previously been reported. This case describes the use of nitroglycerin in the setting of advanced labor to facilitate the placement of a labor epidural.A 35-yr-old, healthy, 90-kg, gravida 3, para 2 parturient admitted to labor and delivery in advanced labor requested an epidural for pain relief. She had two previous uncomplicated normal vaginal deliveries without the use of a labor epidural. A recent cervical examination showed her cervix to be dilated 8 cm, with the fetal head at +1 station. She was moving and uncooperative during contractions, which occurred every 45–60 s. She had not responded to 100 μg intravenous fentanyl given 5 min previously. With difficulty, we managed to position her in a sitting position to administer the epidural. After a sterile preparation of her back with a 10% povidone-iodine solution and 1% lidocaine skin infiltration, we attempted to insert the epidural catheter using a 17-gauge Tuohy needle. However, she kept moving and was uncooperative during and between uterine contractions. After informing the obstetrician and the patient that we were going to administer medication to help ease the painful contractions, we administered three sprays (400 μg per spray dose) of sublingual nitroglycerin (Nitrolingual® Pumpspray; First Horizon Pharmaceutical Corporation, Alpharetta, GA). This produced a temporary decrease in her uterine contractions (reduction in peak uterine pressures and an increased between-contraction interval as measured by external tocodynamometer) and resulted in some transient pain relief. It was then possible to perform the combined spinal–epidural during the interval between contractions. The patient experienced no hypotension or cardiovascular disturbances after administration of the nitroglycerin and resumed her normal uterine contraction pattern within a few minutes. The patient was delivered of a healthy baby vaginally 2 h later, with 1- and 5-min Apgar scores of 8 and 9, respectively.Reducing contraction pain during placement of a labor epidural is potentially beneficial. However, the risks of uterine tocolysis must be balanced with the potential benefit of safer epidural placement and labor analgesia. Although there have been no studies demonstrating increased dural puncture or neural damage after epidural placement in an uncooperative and moving parturient, most clinical anesthesiologists believe that a relation must exist. Decreasing the intensity and frequency of uterine contractions during neuraxial placement in this setting should be potentially advantageous. Remifentanil has been described in this setting to improve analgesia and facilitate the insertion of a labor epidural.6However, potent narcotics have potential adverse effects, in particular maternal apnea, dysphoria, and emesis. Nitroglycerin is a safe, effective uterine tocolytic commonly used in labor, with a rapid onset and brief half-life.2,7Nitroglycerin has minimal, short-lived cardiovascular effects compared with β-adrenergic tocolytics. Although the safety of nitroglycerin during obstetric emergencies seems high, with no adverse maternal or neonatal outcomes,2maternal hypotension and hemodynamics changes are possible, especially if high doses are given.8No more than three metered sprays are recommended within a 15-min period.9A number of studies and case reports describe the use of nitroglycerin in achieving rapid uterine relaxation.2,3,5Nitroglycerin has been used as a tocolytic to reduce uterine hyperactivity,10assist reduction of an inverted uterus,11facilitate intrapartum external cephalic version,12and manage preterm labor contractions.13Nitroglycerin can be administered via a number of routes (intravenous, sublingual, or ointment); however, bioavailability is highly variable between subjects because of a pronounced first-pass metabolism. After sublingual administration, bioavailability is approximately 38%.14Nitroglycerin may be useful in a setting where advanced labor and parturient movement during uterine contractions makes the placement of an epidural difficult and potentially dangerous. It exposes the mother and fetus to minimal risk and, in selected patients, may offer potential benefits justifying its use in this setting. However, physicians should remember that this is “off-label” use of nitroglycerin.9Both the risks and the benefits must be considered, and the patient and her obstetrician must be consulted before uterine tocolytics are administered in this setting.Stanford University School of Medicine, Stanford, California. bcarvalho@stanford.edu

The effect of relcovaptan (SR 49059), an orally active vasopressin V1a receptor antagonist, on uterine contractions in preterm labor

Relcovaptan (SR 49059) is a non-peptide, orally active vasopressin V1a receptor inhibitor. The effect on uterine contractions in 18 women with preterm labor in pregnancy weeks 32–36 was assessed in a double-blind investigation. The inclusion criterion was at least four regular uterine contractions over 30 min as measured by external tocodynamometry. Twelve patients received at random a single oral dose of 400 mg relcovaptan and six received placebo, and contractions were monitored up to 6 h thereafter. Rescue medication (β-adrenoceptor-stimulating drug) was allowed after 2 h. Before drug administration a mean ( ± SE) of 8.2 ± 1.4 and 9.7 ± 1.6 contractions/30 min were recorded in the relcovaptan- and placebo-treated groups, respectively. In the former group, the frequency of uterine contractions started to decrease within the first half hour, and 1.5–2 h after dosing it was steady at 3.2 ± 0.9 contractions/30 min. Correspondingly, after placebo, 7.8 ± 2.2 contractions/30 min were recorded, a statistically significant difference (p = 0.017). The activity in the relcovaptan-treated women remained low, whereas in the placebo group inhibited uterine contractions were observed only in women receiving ‘rescue’ tocolytic treatment. It is concluded that relcovaptan inhibits preterm labor.

Variable intrauterine pressure catheter (IUPC)tracings with two catheters

Variable intrauterine pressure catheter (IUPC)tracings with two catheters

Frequency of uterine contractions in asymptomatic pregnant women with or without a short cervix on transvaginal ultrasound scan

ObjectiveThe purpose of this study was to compare the frequency of uterine contractions in asymptomatic pregnant women with and without a short cervix (<25 mm) on transvaginal ultrasound (TVU) and to determine the additive risk of contractions on the risk of preterm birth. Study designThe study involved secondary analysis of a blinded observational study of asymptomatic singleton pregnancies who were at high risk for preterm birth and who received both home uterine activity monitoring daily and transvaginal ultrasound of the cervix at 22 to 24 and 27 to 28 weeks of gestation. Thresholds for the maximum frequency of uterine contractions of 4 per hour and transvaginal ultrasound cervical length of 25 mm were used for analysis. Contraction frequency was compared in women with cervical length <25 mm and ≥25 mm and was correlated with the risk of spontaneous preterm birth at <35 weeks of gestation. ResultsOf the 303 women whose pregnancy was evaluated at 22 to 24 weeks of gestation, the 39 women (13%) with a cervical length of <25 mm had 1.6 ± 2.7 versus 1.2 ± 2.0 contractions per hour in the 264 women (87%) with a cervical length of ≥25 mm (P=.37). At 27 to 28 weeks of gestation (n=295 women), contraction frequency was 3.2 ± 3.7 versus 2.8 ± 3.1 contractions per hour in women with a cervical length of <25 mm (n=59 women; 20%) versus those with a cervical length of ≥25 mm (n=236 women; 80%; P=.34). Among women with a short cervix, the relative risks for spontaneous preterm birth were 2.0 (95% CI, 0.95-4.2) and 2.1 (95% CI, 1.06-4.3) for women with ≥4 contractions per hour compared with women with <4 contractions per hour at 22 to 24 and 27 to 28 weeks of gestation, respectively. Results were confirmed by logistic regression analysis. ConclusionThe frequency of uterine contractions in asymptomatic women was not related significantly to cervical length of <25 mm versus ≥25 mm. Among women with a cervical length of <25 mm at 22 to 24 or 27 to 28 weeks of gestation, there was a trend toward a 2-fold increased risk of spontaneous preterm birth when the maximum contraction frequency was ≥4 per hour, compared to <4 per hour.