Patterns of human uterine contractions: implications for clinical practice

The overlooked impact of lower uterine segment contractions on second trimester cervical assessment

INTRODUCTION

Asymptomatic contractions in the lower uterine segment (LUS) may affect uterocervical angle and cervical length; however, this has never been investigated. Therefore, the aim of this study was to evaluate the effect of LUS contractions on uterocervical angle, cervical length and LUS thickness.

MATERIALS AND METHODS

This was a prospective, observational, single-cohort study conducted on 102 asymptomatic singleton pregnancies between 19.0 and 22.6 weeks of gestation. Uterocervical angle and cervical length were measured by transvaginal ultrasound at two different time points with an interval of at least 20 minutes. LUS thickness was also measured as an indirect marker of myometrial contraction. A linear and curvilinear regression were performed to explore a potential association between LUS contractions, measured as increments in LUS thickness, and changes in cervical length and uterocervical angle.

RESULTS

The linear regression between changes in LUS thickness and changes in cervical length showed that LUS contractions impact CL; for every one-millimeter increase in LUS thickness, cervical length increased by 0.909 mm, when the isthmus was included in the cervical length measurement (R2=0.358; β=0.909; P<0.001). By contrast, when the isthmus was not included in the measurement, a curvilinear relation between changes in LUS thickness and changes in cervical length was found (R2=0.077; β1=0.575, β2=0.038; P=0.018). The relation between changes in uterocervical angle and changes in LUS thickness was not significant.

DISCUSSION/CONCLUSION

LUS contractions can be observed in many asymptomatic women during the second trimester of pregnancy. LUS contractions lead to an increase in cervical length and LUS thickness, thus impacting ultrasound cervical assessments. These contractions do not affect the uterocervical angle.

Integrated Proteotranscriptomics of Human Myometrium in Labor Landscape Reveals the Increased Molecular Associated With Inflammation Under Hypoxia Stress

During labor, a variety of coordinated physiological and biochemical events cause the myometrium to transition from a quiescent to contractile state; the molecular mechanisms responsible for this transition, however, remain unclear. To better understand this transition at a molecular level, the global transcriptome and proteome of human myometrial samples in labor and those not in labor were investigated through RNA sequencing (RNA-seq) and quantitative liquid chromatography–tandem mass spectrometry (LC-MS/MS) via data-independent acquisition (DIA) and parallel reaction monitoring (PRM) methods. Furthermore, an integrated proteotranscriptomic analysis was performed to explore biological processes and pathway alterations during labor; this analysis identified 1,626 differentially expressed mRNAs (1,101 upregulated, 525 downregulated) and 135 differentially expressed proteins (97 upregulated, 38 downregulated) in myometrium between nonlabor and in labor groups. The comprehensive results of these analyses showed that the upregulated mRNAs and proteins increased inflammation under hypoxia stress in the myometrium under labor, and related proteins and cytokines were validated by PRM and Luminex assays. Our study confirmed the biological process of inflammation and hypoxia in laboring myometrium at the transcriptome and proteome levels and provided recourse to discover new molecular and biological changes during labor.

Later sleep timing is associated with an increased risk of preterm birth in nulliparous women

BACKGROUND

Although uterine contractions have a diurnal periodicity and increase in frequency during hours of darkness, data on the relationship between sleep duration and sleep timing patterns and preterm birth are limited.

OBJECTIVE

We sought to examine the relationship of self-reported sleep duration and timing in pregnancy with preterm birth.

STUDY DESIGN

In the prospective Nulliparous Pregnancy Outcome Study: Monitoring Mothers-to-be cohort, women completed a survey of sleep patterns at 6-13 weeks gestation (visit 1) and again at 22-29 weeks gestation (visit 3). Additionally, at 16-21 weeks gestation (visit 2), a subgroup completed a weeklong actigraphy recording of their sleep. Weekly averages of self-reported sleep duration and sleep midpoint were calculated. A priori, sleep duration of <7 hours was defined as "short," and sleep midpoint after 5 am was defined as "late." The relationships among these sleep characteristics and all preterm birth and spontaneous preterm birth at <37 weeks gestation were examined in univariate analyses. Multivariable logistic regressions that controlled for age and body mass index alone (model 1) and with additional covariates (race, smoking, insurance, and employment schedule) following a backward elimination process (model 2) were performed.

RESULTS

Of the 10,038 women who were enrolled, sleep survey data were available on 7524 women at visit 1 and 7668 women at visit 3. The rate of short sleep duration was 17.1% at visit 1 and 20.7% at visit 3. The proportion with a late sleep midpoint was 11.6% at visit 1 and 12.2% at visit 3. There was no significant relationship between self-reported short sleep and preterm birth across all visits. However, self-reported late sleep midpoint (>5 am) was associated with preterm birth . Women with a late sleep midpoint (>5 am) in early pregnancy had a preterm birth rate of 9.5%, compared with 6.9% for women with sleep midpoint ≤5 am (P=.005). Similarly, women with a late sleep midpoint had a higher rate of spontaneous preterm birth (6.2% vs 4.4%; P=.019). Comparable results were observed for women with a late sleep midpoint at visit 3 (all preterm birth 8.9% vs 6.6%; P=.009; spontaneous preterm birth 5.9% vs 4.3%; P=.023). All adjusted analyses on self-reported sleep midpoint (models 1 and 2) maintained statistical significance (P<.05), except for visit 1, model 2 for spontaneous preterm birth (P=.07). The visit 2 objective data from the smaller subgroup (n=782) demonstrated similar trends in preterm birth rates by sleep midpoint status.

CONCLUSION

Self-reported late sleep midpoint in both early and late pregnancy, but not short sleep duration, is associated with an increased rate of preterm birth.

Absence of circadian rhythms of preterm premature rupture of membranes and preterm placental abruption

PURPOSE

Data regarding circadian rhythm in the onset of spontaneous preterm premature rupture of membranes (PROM) and placental abruption (PA) cases are conflicting. We modeled the time of onset of preterm PROM and PA cases and examined if the circadian profiles varied based on the gestational age at delivery.

METHODS

We used parametric and nonparametric methods, including trigonometric regression in the framework of generalized linear models, to test the presence of circadian rhythms in the time of onset of preterm PROM and PA cases among 395 women who delivered a singleton between 2009 and 2010 in Lima, Peru.

RESULTS

We found a diurnal circadian pattern, with a morning peak at 07:32 AM (95% confidence interval, 05:46 AM–09:18 AM) among moderate preterm PROM cases (P value < .001), and some evidence of a diurnal circadian periodicity among PA cases in term infants (P value = .067). However, we did not find evidence of circadian rhythms in the time of onset of extremely or very preterm PROM (P value = .259) and preterm PA (P value = .224).

CONCLUSIONS

The circadian rhythms of the time of onset of preterm PROM and PA cases varied based on gestational weeks at delivery. Although circadian rhythms were presented among moderate preterm PROM and term PA cases, there was no evidence of circadian rhythms among preterm PA and very or extremely preterm PROM cases, underlying other mechanisms associated with the time of onset.

Exploring the effect of hospital admission on contraction patterns and labour outcomes using women's perceptions of events

OBJECTIVE

this study investigated the phenomenon of spontaneous labour contractions becoming less frequent on admission to hospital, which is observed anecdotally but is not evident in the literature. Anxiety in response to hospitalisation has been proposed to be responsible by initiating the biochemical response termed 'fight or flight'.

DESIGN

A non-experimental prospective design and a combination of quantitative and qualitative analysis. Data were collected using self-report labour diaries, postnatal questionnaires and hospital records of labour. Univariate analysis using t-test and chi(2)-test was performed to examine relationships between variables, and content analysis was undertaken on qualitative data regarding reactions to hospitalisation.

SETTING

hospital and community maternity services provided by a National Health Service hospital in Southern England in 1997.

PARTICIPANTS

about 87 women at least 37-week gestation, uncomplicated singleton pregnancy anticipating spontaneous labour with a live fetus.

MEASUREMENTS AND FINDINGS

labour diaries were analysed from 26 births. In three home births and 11 hospital births, labour contractions became more frequent, but in the remaining 12 labours, contractions decreased after admission to hospital. Women whose contractions slowed were not more anxious, but they rarely had cervical dilatation over 5cm and usually assumed a recumbent position in hospital. Artificial rupture of membranes was performed more frequently in these women, they used more pain relief and had a higher incidence of complicated childbirth; however, these differences were not statistically significant.

KEY CONCLUSIONS

labour contractions can increase or decrease in frequency following admission to hospital, and the change of frequency may be associated with stage of cervical dilatation and posture rather than anxiety.

IMPLICATIONS FOR PRACTICE

routine intervention to speed up labour on the basis of admission observations is called into question, and women should be made aware that slowing of contractions can occur as a normal part of changing the labour environment. Further research is needed to determine the physiological parameters of spontaneous labour and the role of posture in labour progress is needed.

Alteration in uterine contractility in mares with experimentally induced placentitis

An experimental model of ascending placentitis was developed in the mare to characterize the uterine myoelectrical pattern in late gestation and determine how ascending placentitis altered this pattern. In experiment 1, myometrial electrical activity was analyzed during the early morning, late morning and evening hours in four mares in the last 15 days of gestation to identify patterns of activity. In experiment 2, nine mares received intra-cervical inoculations ofStreptococcus equisubspecieszooepidemicus. Myoelectrical activity in the early morning and evening hours in these mares was compared with four control mares. In experiment 1, the number of spike burst clusters >30 s was greater in the evening than in the late morning hours (P< 0.04). Spike burst activity (number × duration) of mares in experiment 1 was similar during day and night recordings until the last 6 days of gestation when it gradually increased each evening until parturition (P< 0.05). In experiment 2, control mares experienced a gradual increase in the number of small spike burst clusters in the last 6 days (P= 0.008) and an increase in large and small spike burst clusters in the evening hours in the last 4 days of gestation (P= 0.03). Mares with experimentally induced placentitis never exhibited a rise in spike burst clusters but had an increase in the mean duration and activity index of large spike burst clusters in the 4 days before parturition (P< 0.04). In conclusion, control mares had a progressive, reversible rise in myoelectrical activity at night in the week preceding parturition. This was not observed in mares with experimentally induced placentitis. They exhibited an increase in the intensity and duration of large spike burst clusters possibly in response to local inflammation.

Current status of home uterine activity monitoring

A comprehensive evidence-based review of the clinical data leads to the conclusion that if patients at high risk for preterm birth (eg, prior preterm birth because of preterm labor, twins and higher-order multiple gestation, women who have preterm labor during the current pregnancy tocolyzed effectively) use the comprehensive system of HUAM correctly (ie, daily nursing care and twice-daily monitoring) with appropriate alarm rates and sensitive monitors, the incidence of early diagnosis of preterm labor, effective prolongation of pregnancy with fewer preterm births, and a reduction in neonatal morbidity is always demonstrated when the study group is compared with a control group consisting of women receiving standard care available to obstetricians in the United States. The authors expect that there will always be arguments regarding whether the monitor or the nurse contributes most to preterm birth reduction. Even when the alerts of detected contractions or patient-reported symptoms are sounded, the issue of prompt and effective medical intervention will always be hotly debated. The appropriate research design that tests HUAM while allowing various diagnostic and treatment modalities that physicians employ around the United States must be individualized. Physicians must make the decision, based on the evidence, regarding whether or not this system would benefit their patients. While investigators argue about research designs and statistical analyses, physicians simply want the best outcomes for their patients, which is what women and the whole of society also want. Based on the available evidence, it is clear that when the comprehensive system of HUAM is used appropriately in the right patients, everyone benefits.

Effect of magnesium sulfate, isradipine, and ritodrine on contractions of myometrium: pregnant human and rat

BACKGROUND

Magnesium sulfate, isradipine, and ritodrine are smooth muscle relaxants used for treating preterm labor. The aim of this study is to investigate the action profile of these drugs on the amplitude and frequency of spontaneous contractions of isolated myometrial strips of pregnant human and rat.

MATERIAL AND METHODS

Isolated myometrial strips were obtained from humans undergoing elective cesarean section at term pregnancy and Wistar albino rats on gestational days 19-21. These strips were mounted in organ baths for recording of isometric tensions. The effect of magnesium sulfate, isradipine, and ritodrine on the amplitude and frequency of spontaneous contractions was compared with the anova test.

RESULTS

Ritodrine (10-8-10-5 M) concentration-dependently inhibited the frequency and amplitude of spontaneous contractions of myometrial strips. At 10-4 M, tachyphylaxis of ritodrine occurred and contractions started again. Magnesium sulfate (10-7-10-4 M) inhibited the frequency but did not change the amplitude of the spontaneous contractions. Isradipine (10-7-10-4 M) had a concentration-related inhibitor effect on both the frequency and amplitude of the spontaneous contractions. The effects of magnesium sulfate, isradipine, and ritodrine were considerably similar in myometrium strips obtained from pregnant rats and humans.

CONCLUSIONS

Because of tachyphylaxis, the effectiveness of ritodrine is limited for inhibition of myometrial contractions. Magnesium sulfate reduced the frequency of spontaneous contractions without affecting the amplitude. Isradipine may be an interesting therapeutic alternative in situations where inhibition of uterine activity is desirable.