Effect of nipple stimulation on uterine activity and on plasma levels of oxytocin in full term, healthy, pregnant women

The effect of nipple stimulation on uterine activity, foetal heart rate and plasma oxytocin level in healthy full term pregnant women was studied. Ten women in weeks 38-39 of pregnancy stimulated their nipples for 30 min. Nine of the ten experienced uterine contractions. One woman showed signs uterine hyperactivity (frequent contractions) and foetal heart rate decelerations. Blood samples were drawn at 15 s intervals during 5-6 contractions and oxytocin levels were measured with radioimmunoassay. Oxytocin levels rose significantly during the nipple stimulation and short bursts of oxytocin were recorded during contractions. Nipple stimulation has been used to induce labour and our data may suggest that oxytocin released in response to such stimulation is responsible for the contractions induced.     

Antepartal uterine hypercontractility secondary to nipple stimulation

An alarming result was noted in conjunction with a nipple stimulation contraction stress test. In a 42-week pregnant woman with suspected postmaturity, gentle self-stimulation of the right nipple through the clothing for one to 1.5 minutes caused the sudden onset of uterine hypercontractility, increased uterine tone, and severe fetal bradycardia. The bradycardia persisted for approximately five minutes despite supportive measures. Operative delivery was being considered when the fetal heart rate returned to a normal baseline. Ultimately, the patient delivered vaginally without further significant complication. This experience demonstrated that carefully controlled breast stimulation may result in unpredictable uterine hyperstimulation with fetal bradycardia.     

Comparison of the nipple stimulation and exogenous oxytocin contraction stress tests. A randomized, prospective study

In a prospective, randomized trial, 103 women underwent a total of 203 antenatal stress tests. One hundred four nipple stimulation contraction stress tests (BSTs) and 99 oxytocin challenge tests (OCTs) were performed. The patient populations were similar for the two groups. Uterine hyperstimulation with abnormal fetal heart rate patterns occurred with 2.9% and 1% of the BSTs and OCTs, respectively. The failure rate for the BST group was 22%. Maternal age and weight, parity and gestational age were not associated with test failure. Only one patient failed more than one BST, but she did not fail every such test. When test time (time from initiation to completion of the test) was compared between the two groups, a significant difference was found when the BST was successful. However, when test time in the total BST group (successful and unsuccessful BSTs followed by an OCT was compared to that in the OCT group, no difference could be found. Though an OCT following an unsuccessful BST took longer to perform than did a primary OCT, the difference was not statistically significant. It appears that BST test failure may relate more to the technique of nipple stimulation used than to intrinsic patient factors.     

Contraction stress test by intermittent nipple stimulation

Although the nonstress test has generally supplanted the contraction stress test as the primary test for assessment of fetal well-being, the contraction stress test continues to be useful. Objectionable factors of the contraction stress test have included the time required to complete the test and the frequent necessity for intravenous oxytocin. The authors developed a contraction stress test protocol using contractions produced by intermittent nipple stimulation and used the method for 345 tests on 193 high-risk pregnancies during a 15-month period. The women were instructed to stimulate one breast, through their clothes, for two minutes and then to rest for five minutes. This cycle was repeated as necessary, but was interrupted whenever contractions began. Using this protocol, the authors were successful in achieving an adequate contraction frequency with every attempt, and hyperstimulation was not more frequent than previously reported with the standard contraction stress test. The average time requirement was 45 minutes. No unexplained stillbirths occurred after a negative test.     

Changes in the Bishop score induced by manual nipple stimulation. A cross-over randomized study

Bishop score changes, by a cross-over, randomized study, were evaluated in 60 primigravidas at term, not yet in labour, who performed nipple stimulation for 45 minutes three times a day for three days. Results showed that changes of Bishop score in the treated groups were statistically highly significant, in comparison to control groups. A greater frequency in the onset of labour was also remarked.     

Sweeping of the membranes versus uterine stimulation by oxytocin in nulliparous women. A randomized controlled trial

The aim of this study was to evaluate whether sweeping of the membranes at term could shorten the length of pregnancy and reduce the incidence of postterm pregnancies. We randomly selected 104 nulliparas with uncomplicated pregnancy and gestational age between 281 and 287 days. Our patients were divided into three groups. Group A consisted of 34 women who were subjected to sweeping of the membranes. Uterine stimulation with oxytocin was applied in 35 women (group B), and 35 women (group C) were used as a control group. We had no significant reduction of the time interval from sweeping of the membranes until delivery (1.9 +/- 1.2 days), compared to that of group B (2.1 +/- 0.8 days) as well as that of the control group (2.5 +/- 0.9 days). The incidence of spontaneous labor in patients after sweeping of the membranes was greater (67.6%) when compared with oxytocin-stimulated patients and the control group (p < 0.05). Furthermore, a better Bishop score was noted in patients of group A. No statistically significant difference was noted in the mode of delivery between the groups, but sweeping of the membranes significantly decreased the incidence of postterm pregnancies (p < 0. 05). We concluded that sweeping of the membranes is an effective method for initiating labor in women with a gestational age between 40 and 41 weeks, thus reducing the need for induction.     

Excessive uterine activity accompanying induced labor

OBJECTIVE: To estimate the incidence and timing of excessive uterine activity accompanying induction of labor with misoprostol using different routes (oral or vaginal) and forms (intact tablet or crushed) and to compare these with dinoprostone gel, oxytocin, and spontaneous labor. METHODS: This retrospective cohort study included 519 women at term who had labor induced and 86 women at term in spontaneous labor. Induction agents included misoprostol, dinoprostone, or oxytocin. Fetal heart rate and uterine activity tracings were analyzed independently by three maternal-fetal medicine physicians. The diagnosis of tachysystole or hyperstimulation required the agreement of two or more reviewers. RESULTS: The incidence of tachysystole was highest with misoprostol administered by vaginal tablet (misoprostol vaginal tablet 50 microg every 4 hours, 48.6%; vaginal tablet crushed 50 microg and suspended in hydroxyethyl gel every 4 hours, 30.7%, P =.009; oral tablet 50 microg every 4 hours, 22.2%, P =.001; oral tablet crushed 50 microg every 4 hours, 15.5%, P <.001; dinoprostone gel, 33.0%, P =.022; intravenous oxytocin, 30.2%, P =.027; and spontaneous onset of labor, 23.3%, P <.001). Hyperstimulation occurred more often with dinoprostone gel (16.5%) than with other forms of induction or spontaneous labor. Hyperstimulation occurred significantly more often with vaginal misoprostol crushed tablet (7.9%) and vaginal misoprostol intact tablet (7.6%) than with crushed oral misoprostol (1.0%) (P =.016 and.018, respectively). There was a shorter time to tachysystole with increasing doses of vaginal misoprostol tablet (P =.01). CONCLUSION: The incidence of tachysystole and hyperstimulation, and time to tachysystole, varied depending on the route and form of misoprostol given.     

Breast stimulation contraction stress test: uterine contractions in the absence of oxytocin release

The contraction stress test has been widely used to manage high-risk pregnancies. Breast-stimulated uterine contractions have been assumed to be mediated through oxytocin release. We studied 20 women undergoing a breast-stimulated contraction stress test. There was no significant increase in plasma oxytocin levels during this study in either test responders or nonresponders. These results suggest that the presence of a breast stimulation-uterine contraction reflex is not mediated by oxytocin.     

The effect of oxytocin infusion on uterine activity levels in slow labour

Uterine activity was studied in 31 women who were progressing slowly in spontaneous labour. In 75%, levels of uterine activity were below the tenth centile for normal spontaneous labour (mean uterine activity integral, UAI, 593 kPas/15 min; SD 296). Following oxytocin infusion, there was a significant increase in uterine activity to a mean of 1124 kPas/15 min (SD 276), which was the same as in normal spontaneous labour. The response to oxytocin was dependent upon the pre-existing level of uterine activity, and sensitivity to oxytocin, rather than the dose rate; 84% responded to infusion rates of less than 8 mU/min. The response to oxytocin was best expressed in terms of active contraction area (uterine activity integral, UAI) or Montevideo units, rather than the frequency or active pressure of contractions. The rate of cervical dilatation following oxytocin augmentation could not be predicted either by the increase in uterine activity or by the actual level of activity achieved.     

The effect of oxytocin infusion on uterine activity levels in slow labour

Summary. Uterine activity was studied in 31 women who were progressing slowly in spontaneous labour. In 75%, levels of uterine activity were below the tenth centile for normal spontaneous labour (mean uterine activity integral, UAI, 593 kPas/15 min; SD 296). Following oxytocin infusion, there was a significant increase in uterine activity to a mean of 1124 kPas/15 min (SD 276), which was t h e same as in normal spontaneous labour. The response t o oxytocin was dependent upon the pre-existing level of uterine activity, and sensitivity to oxytocin, rather than the dose rate; 84% responded t o infusion rates of < 8 mU/min. The response t o oxytocin was best expressed in terms of active contraction area (uterine activity integral, UAI) or Montevideo units, rather than the frequency or active pressure of contractions. The rate of cervical dilatation following oxytocin augmentation could not be predicted either by t h e increase in uterine activity or by the actual level of activity achieved.     

缩宫素对超声消融治疗子宫肌瘤效果的影响

目的 探讨缩宫素对超声消融治疗子宫肌瘤效果的影响.方法 采用MRI引导下的超声消融肿瘤治疗系统,以单点辐照的方式,选择确诊的26例子宫肌瘤患者的29个肌瘤中的82个靶点进行研究,比较使用缩宫素前、后辐照单点达到60℃时所需的能量、时间及升高单位温度(1℃)所需的能量.结果 使用缩宫素前,辐照单点温度达到60℃所需的能量为(5320±910)J,时间为(21±20)s,升高1 ℃所需的能量为(255±302)J;静脉滴注缩宫素后,辐照单点温度达到60℃所需的能量为(2890±325)J,时间为(12±7)s,升高1℃所需的能量为(126±94)J.使用缩宫素前、后,各指标间比较,差异均有统计学意义(P值分别为0.002、0.001、0.002).结论 缩宫素能明显降低超声消融治疗子宫肌瘤所需的能量,缩短治疗时间,从而提高治疗效率,具有很好的临床应用价值.

Abstract：

Objective To explore the effect of oxytocin on uterine fibroids treated by ultrasound ablation. Methods Eighty-two single points in 29 uterine fibroids from 26 patients were sonicated with magnetic resonance imaging guided by high intensity focused ultrasound before and after using oxytocin. The required total energy, sonication time required to reach 60 ℃ and the acoustic energy for increasing 1 ℃ of temperature at the single point before and after using oxytocin were compared. Results Before intravenous infusion of oxytocin, the average total sonication energy required to reach 60 ℃ was (5320 ±910) J and it took (21 ±20) seconds for sonicating a single point, the energy required for increasing 1 ℃ was (255 ± 302) J. In contrast, after intravenous infusion of oxytocin, the average total sonication energy required to reach 60 ℃ was (2890 ±325) J, and it took (12 ±7) seconds for sonicating a single point, the energy required for increasing 1 ℃ was ( 126 ± 94 ) J. Those three index all reached statistical difference ( P = 0.002, P = 0.001, P= 0.002, respectively). Conclusion It seemed that Oxytocin could significantly decrease the energy required for ablating uterine fibroids, shorten treatment time and improve the treatment efficiency.     

Characteristics of uterine activity during the breast stimulation stress test

Characteristics of uterine activity produced by nipple stimulation were studied in 185 consecutive breast stimulation stress tests. Adequate contractions were produced in 95.6% of tests. Exaggerated uterine response (contractions occurring more than once every two minutes or lasting more than 90 seconds) was present in 45.5% of the patients. Twenty-one percent of the patients with such uterine activity also had a fetal heart rate (FHR) deceleration (hyperstimulation breast stimulation stress test), without adverse fetal outcome. The time in minutes from start of nipple stimulation to the first contraction (stimulation contraction interval) was recorded for each patient. Significant difference was not observed in the stimulation contraction interval distribution between the groups with and without exaggerated uterine activity. The authors conclude that there is a relatively high incidence of exaggerated uterine activity response to the breast stimulation stress test and that close surveillance of mother and fetus is warranted during antepartum nipple stimulation.     

Changes in electromyographic activity of the cervix after stimulation of labour with oxytocin

The electrical activity of the cervix can be measured during labour. The influence of oxytocin on electromyographic (EMG) activity of the cervical musculature was studied in 80 primiparous women after induction of labor. The highest electrical activity registered at the time of uterine contraction and between two contractions was used for analysis. The basic pattern of oxytocin-produced changes in muscular contractions in the cervix observed via EMG activity is that of the activity increasing with contractions of the uterine corpus and diminishing between contractions. The effect of oxytocin on cervical musculature is different in ripe and unripe cervices.