Relationship of circadian rhythms of uterine activity with term and preterm delivery

Labour classified by cervical dilatation & fetal membrane rupture demonstrates differential impact on RNA-seq data for human myometrium tissues

High throughput sequencing has previously identified differentially expressed genes (DEGs) and enriched signalling networks in human myometrium for term (≥37 weeks) gestation labour, when defined as a singular state of activity at comparison to the non-labouring state. However, transcriptome changes that occur during transition from early to established labour (defined as ≤3 and >3 cm cervical dilatation, respectively) and potentially altered by fetal membrane rupture (ROM), when adapting from onset to completion of childbirth, remained to be defined. In the present study, we assessed whether differences for these two clinically observable factors of labour are associated with different myometrial transcriptome profiles. Analysis of our tissue (‘bulk’) RNA-seq data (NCBI Gene Expression Omnibus: GSE80172) with classification of labour into four groups, each compared to the same non-labour group, identified more DEGs for early than established labour; ROM was the strongest up-regulator of DEGs. We propose that lower DEGs frequency for early labour and/or ROM negative myometrium was attributed to bulk RNA-seq limitations associated with tissue heterogeneity, as well as the possibility that processes other than gene transcription are of more importance at labour onset. Integrative analysis with future data from additional samples, which have at least equivalent refined clinical classification for labour status, and alternative omics approaches will help to explain what truly contributes to transcriptomic changes that are critical for labour onset. Lastly, we identified five DEGs common to all labour groupings; two of which (AREG and PER3) were validated by qPCR and not differentially expressed in placenta and choriodecidua.

Low CLOCK and CRY2 in 2nd trimester human maternal blood and risk of preterm birth: A nested case-control study

Previous studies have observed an association between maternal circadian rhythm disruption and preterm birth (PTB). However, the underlying molecular mechanisms and the potential of circadian clock genes to serve as predictors of PTB remain unexplored. We examined the association of 10 core circadian transcripts in maternal blood with spontaneous PTB (sPTB) vs term births using a nested case-control study design. We used a public gene expression dataset (GSE59491), which was nested within the All Our Babies (AOB) study cohort in Canada. Maternal blood was sampled in trimesters 2-3 from women with sPTB (n = 51) and term births (n = 106), matched for 5 demographic variables. In 2nd trimester maternal blood, only CLOCK and CRY2 transcripts were significantly lower in sPTB vs term (p = 0.02 ~ 0.03, FDR < 0.20). A change of PER3 mRNA from trimesters 2 to 3 was significantly associated with sPTB (decline in sPTB, p = 0.02, FDR < 0.20). When CLOCK and CRY2 were modeled together in 2nd trimester blood, the odds ratio of being in the low level of both circadian gene transcripts was greater in sPTB vs term (OR = 4.86, 95%CI = (1.75,13.51), p < 0.01). Using GSVA and Pearson correlation, we identified 98 common pathways that were negatively or positively correlated with CLOCK and CRY2 expression (all p < 0.05, FDR < 0.10). The top three identified pathways were amyotrophic lateral sclerosis, degradation of extracellular matrix, and inwardly rectifying potassium channels. These three processes have previously been shown to be involved in neuron death, parturition, and uterine excitability during pregnancy, respectively.

Pregnancy Induces an Earlier Chronotype in Both Mice and Women

Daily rhythms generated by endogenous circadian mechanisms and synchronized to the light-dark cycle have been implicated in the timing of birth in a wide variety of species. Although chronodisruption (e.g., shift work or clock gene mutations) is associated with poor reproductive outcomes, little is known about circadian timing during pregnancy. This study tested whether daily rhythms change during full-term pregnancies in mice and women. We compared running wheel activity continuously in both nonpregnant ( n = 14) and pregnant ( n = 13) 12- to 24-week-old C57BL/6NJ mice. We also monitored wrist actigraphy in women ( N = 39) for 2 weeks before conception and then throughout pregnancy and measured daily times of sleep onset. We found that on the third day of pregnancy, mice shift their activity to an earlier time compared with nonpregnant dams. Their time of daily activity onset was maximally advanced by almost 4 h around day 7 of pregnancy and then shifted back to the nonpregnant state approximately 1 week before delivery. Mice also showed reduced levels of locomotor activity during their last week of pregnancy. Similarly, in women, the timing of sleep onset was earlier during the first and second trimesters (gestational weeks 4-13 and 14-27) than before pregnancy and returned to the prepregnant state during the third trimester (weeks 28 until delivery). Women also showed reduced levels of locomotor activity throughout pregnancy. These results indicate that pregnancy induces changes in daily rhythms, altering both time of onset and amount of activity. These changes are conserved between mice and women.

Opening the Debate: How to Fulfill the Need for Physicians' Training in Circadian-Related Topics in a Full Medical School Curriculum

BACKGROUND

Circadian rhythms are daily changes in our physiology and behavior that are manifested as patterns of brain wave activity, periodic hormone production, recurring cell regeneration, and other oscillatory biological activities. Their importance to human health is becoming apparent; they are deranged by shift work and jet-lag and in disparate conditions such as insomnia, sleep syndromes, coronary heart attacks, and depression, and are endogenous factors that contribute to cancer development and progression.

DISCUSSION

As evidence of the circadian connection to human health has grown, so has the number of Americans experiencing disruption of circadian rhythms due to the demands of an industrialized society. Today, there is a growing work force that experiences night shift work and time-zone shifts shaping the demands on physicians to best meet the needs of patients exposed to chronic circadian disruptions. The diverse range of illness associated with altered rhythms suggests that physicians in various fields will see its impact in their patients. However, medical education, with an already full curriculum, struggles to address this issue.

SUMMARY

Here, we emphasize the need for incorporating the topic of circadian rhythms in the medical curriculum and propose strategies to accomplish this goal.

Guidelines for Physical Activity during Pregnancy: Comparisons From Around the World

INTRODUCTION

Women attain numerous benefits from physical activity during pregnancy. However, due to physical changes that occur during pregnancy, special precautions are also needed. This review summarizes current guidelines for physical activity among pregnant women worldwide.

METHODS

We searched PubMed (MedLINE) for country-specific governmental and clinical guidelines on physical activity during pregnancy through the year 2012. We cross-referenced with articles referring to guidelines, with only the most recent included. An abstraction form was used to extract key details and summarize.

RESULTS

In total, 11 guidelines were identified from nine countries (Australia, Canada, Denmark, France, Japan, Norway, Spain, United Kingdom, United States). Most guidelines supported moderate intensity physical activity during pregnancy (10/11) and indicated specific frequency (9/11) and duration/time (9/11) recommendations. Most guidelines provided advice on initiating an exercise program during pregnancy (10/11). Six guidelines included absolute and relative contraindications to exercise. All guidelines generally ruled-out sports with risks of falls, trauma, or collisions. Six guidelines included indications for stopping exercise during pregnancy.

CONCLUSION

This review contrasted pregnancy-related physical activity guidelines from around the world, and can help to inform new guidelines as they are created or updated, and facilitate the development of a worldwide guideline.

A blueprint for the prevention of preterm birth: vaginal progesterone in women with a short cervix

Preterm birth is the leading cause of perinatal morbidity and mortality worldwide, and is the most important challenge to modern obstetrics. A major obstacle has been that preterm birth is treated (implicitly or explicitly) as a single condition. Two thirds of preterm births occur after the spontaneous onset of labor, and the remaining one third after "indicated" preterm birth; however, the causes of spontaneous preterm labor and "indicated" preterm birth are different. Spontaneous preterm birth is a syndrome caused by multiple etiologies, one of which is a decline in progesterone action, which induces cervical ripening. A sonographic short cervix (identified in the midtrimester) is a powerful predictor of spontaneous preterm delivery. Randomized clinical trials and individual patient meta-analyses have shown that vaginal progesterone reduces the rate of preterm delivery at <33 weeks of gestation by 44%, along with the rate of admission to the neonatal intensive care unit, respiratory distress syndrome, requirement for mechanical ventilation, and composite neonatal morbidity/mortality score. There is no evidence that 17-α-hydroxyprogesterone caproate can reduce the rate of preterm delivery in women with a short cervix, and therefore, the compound of choice is natural progesterone (not the synthetic progestin). Routine assessment of the risk of preterm birth with cervical ultrasound coupled with vaginal progesterone for women with a short cervix is cost-effective, and the implementation of such a policy is urgently needed. Vaginal progesterone is as effective as cervical cerclage in reducing the rate of preterm delivery in women with a singleton gestation, history of preterm birth, and a short cervix (<25 mm).

Uterine electromyogram database and processing function interface: An open standard analysis platform for electrohysterogram signals

The uterine electromyogram or electrohysterogram (EHG) is one of the most promising biophysical markers of preterm labor. At this time no recording parameter standard exists for EHG recordings which can be a problem for the establishment of international multicentric trials. In this paper, we present a management and processing system dedicated to storing and processing EHG signals. This system can process EHG signals recorded in different experimental conditions i.e. different sampling frequencies. The signal management is performed using an easy to use graphical user interface. Other available functions include visualization, preprocessing and analysis of EHG signals. The proposed processing functions provide temporal, spectral and time-scale parameters obtained from the EHG bibliography. The obtained results from real signals recorded in two different hospitals in two different countries are in accordance with the literature and demonstrate the potential of the proposed system. The incorporation of new functions is easy, due to a standardization of the EHG data formats.

A prospective masked observational study of uterine contraction frequency in twins

OBJECTIVE

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.

STUDY DESIGN

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.

RESULTS

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.

CONCLUSION

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.

Does regular massage from late pregnancy to birth decrease maternal pain perception during labour and birth?—A feasibility study to investigate a programme of massage, controlled breathing and visualization, from 36 weeks of pregnancy until birth

The present study was undertaken to produce a detailed specification of a programme of massage, controlled breathing and visualization performed regularly by birth partners, from 36 weeks gestation and assisted by a trained professional, following hospital admission during labour and birth. As current research on massage interventions for pain relief in labour is poorly characterized, we began by undertaking a feasibility study on an established massage programme [Goldstone LA. Massage as an orthodox medical treatment past and future. Complementary Therapies in Nursing & Midwifery. 2000;6:169-75]. The intervention was designed in light of experimental findings that repeated massage sessions over 14 days increases pain threshold, by an interaction between oxytocin and opioid neurons [Lund I, Yu L-C, Uvnas-Moberg K, Wang J, Yu C, Kurosawa M, et al. Repeated massage-like stimulation induces long-term effects on nociception: contribution of oxytocinergic mechanisms. European Journal of Neuroscience 2002;16:330-8]. A 4 week time-frame was selected to coincide with a physiological increase in maternal pain threshold [Cogan R, Spinnato JA. Pain and Discomfort Thresholds in Late Pregnancy. Pain 1986;27:63-8, Whipple B, Josimovich JB, Komisaruk BR. Sensory thresholds during the antepartum, intrapartum, and postpartum periods. International Journal of Nursing Studies 1990;27(3):213-21, Gintzler AR, Komisaruk BR. Analgesia is produced by uterocervical mechano-stimulation in rats: roles of afferent nerves and implications for analgesia of pregnancy and parturition. Brain Research 1991;566:299-302, Gintzler AR, Liu N-J. The maternal spinal cord: biochemical and physiological correlates of steroid-activated antinociceptive processes. In: Russell JA, Douglas AJ, Windle RJ, Ingram CD, editors., Progress in Brain Research. Volume 133. The Maternal Brain. Neurobiological and Neuroendocrine adaptation and disorders in pregnancy and postpartum. Amsterdam: Elsevier Science, 2001. p. 83-97]. The main objective was to measure the effects of the programme on maternal pain perception during labour and birth. To detect any effect of massage during labour, on maternal cortisol and catecholamines, cord venous blood was taken to measure plasma concentrations following birth. Twenty-five nulliparous (N) and 10 multiparous (M) women participated in the study. Cortisol values were similar to published studies following labour without massage but pain scores on a Visual Analogue Scale (VAS), at 90min following birth were significantly lower than scores recorded 2 days postpartum [Capogna G, Alahuhta S, Celleno D, De Vlieger H, Moreira J, Morgan B, et al. Maternal expectations and experiences of labour pain and analgesia: a multi-centre study of nulliparous women. International Journal of Obstetric Anaesthesia 1996;5:229-35]. The mean score was 6.6. Previous studies suggest that a reduction from 8.5 to 7.5 would significantly reduce pharmacological analgesia in labour [Capogna G, Alahuhta S, Celleno D, De Vlieger H, Moreira J, Morgan B, et al. Maternal expectations and experiences of labour pain and analgesia: a multi-centre study of nulliparous women. International Journal of Obstetric Anaesthesia 1996;5:229-35].

Physical exertion at work and the risk of preterm delivery and small-for-gestational-age birth

OBJECTIVE

To assess whether exposure to standing, lifting, night work, or long work hours during 3 periods of pregnancy are associated with an increased risk of preterm or small-for-gestational-age birth.

METHODS

The Pregnancy, Infection and Nutrition study is a prospective cohort with a nested case-control component that was conducted through clinic and hospital settings in Central North Carolina. A total of 1,908 women pregnant with a singleton gestation were recruited during prenatal visits from January 1995 through April 2000 and provided information during telephone and face-to-face interviews about physical exertion for the 2 longest-held jobs during pregnancy.

RESULTS

No significant elevations in preterm delivery were observed among women who lifted repeatedly or stood at least 30 hours per week, with no changes in risk estimates over the course of pregnancy. A 50% elevation in the risk of preterm delivery (relative risk 1.5, 95% confidence interval 1.0-2.0; first trimester) was observed among women who reported working at night (10:00 PM to 7:00 AM), whereas a 40% reduction in risk was observed among women working at least 46 hours per week (relative risk 0.6, 95% confidence interval 0.4-0.9; first trimester), regardless of period of exposure. No elevations in small-for-gestational-age birth were observed among women exposed to any of the 4 types of occupational exertion.

CONCLUSION

Physically demanding work does not seem to be associated with adverse pregnancy outcomes, whereas working at night during pregnancy may increase the risk of preterm delivery. Studies to examine the effect of shift work on uterine activity would help to clarify the possibility of a causal effect on preterm birth.

Uterine contraction assessment

Few approaches to preterm birth prevention have been as thoroughly studied yet as enigmatic as uterine contraction assessment. Despite multiple randomized clinical trials (level 1 evidence), the effectiveness of home uterine contraction assessment as an adjunct to the clinical management of women at risk for preterm birth remains controversial. This article reviews these trials with particular attention to study design and patient inclusion criteria. The data are absolutely clear that home uterine contraction monitoring with or without frequent perinatal nursing contact can reduce the risk of preterm birth and improve perinatal outcomes and that both are independently superior to standard preterm birth prevention education and care.

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

We present findings suggesting that photoperiod is important in determining the sensitivity of the late-pregnant rabbit uterus to oxytocin (OT). Longitudinal myometrial strips were taken from term-pregnant and estrous rabbits and mounted in an organ bath for isometric myographic recording at different times during a 16:8-h light-dark cycle (lights on 0600–2200; n = 5/group), and the strength of contractions was registered in response to the application of OT or KCl. Strength of contractions was dose dependent and was up to 200 times greater at doses three to four orders of magnitude lower in tissue taken from pregnant animals during the light phase (0700 and 1300) than during the dark phase (2400 and 0400). Strips from nonpregnant estrous females also showed greater sensitivity and contractile force when taken in the light (0700) than in the dark (0400), although the differences were not significant. Consistent with the influence of photoperiod on uterine sensitivity to OT, strips taken from two groups of pregnant females ( n = 5/group) maintained on a light-dark cycle advanced 12 h showed significantly greater sensitivity and force in response to OT during the new subjective light than during the new subjective dark phase. The photoperiod-dependent contractile response to OT was specific and not simply the result of a change in general mechanical properties of the muscle, because administration of KCl resulted in dose-dependent contractions of similar magnitude in both the light and dark phase. These results are consistent with the fact that rabbits, like other nocturnal mammals, typically give birth during the day.

24 hour rhythm in the timing of pre-labour spontaneous rupture of membranes at term

OBJECTIVE

To study the timing of pre-labour spontaneous rupture of membranes (SROM) in term pregnancies.

DESIGN

Prospective cohort.

SETTING

A maternity hospital in the United Kingdom.

SAMPLE

Women who were more than 37 weeks gestation with confirmed spontaneous rupture of membranes and not in labour after 4 h.

METHODS

Women who were admitted into labour ward with a diagnosis of spontaneous rupture of membranes after 37 weeks of gestation were included. The women's demographic details were recorded and inquiries about whether they had sexual intercourse in the preceding 12 h. The final outcome of their pregnancy was recorded and analysed.

MAIN OUTCOME MEASURES

(1) The exact time of spontaneous rupture of membranes, (2) the time of onset of spontaneous labour, (3) delivery details.

RESULTS

One hundred and ninety-six women were studied. A 24 h rhythm in the timing of spontaneous rupture of membranes was found with 33.2% occurring between 00:00 and 04:00 h. When contractions representing the onset of labour occurred there was no diurnal rhythm to the timing of onset of contractions.

CONCLUSIONS

There is a 24 h rhythm in the timing of spontaneous rupture of membranes in term gestations. The physiological reasons for this rhythm are not understood at the present time.

Retained placenta in Friesian mares: incidence, and potential risk factors with special emphasis on gestational length

During the foaling seasons of 1999 and 2000, the incidence of retained placenta in 495 normal parturitions of 436 Friesian brood mares was studied. Retained placenta was defined as a failure to expel all fetal membranes within 3 h of the delivery of the foal. Furthermore, the sex of the foal, month of breeding, sire and dam's sire, age of the mare, and time of day of foaling, were studied as factors that might be associated with retained placenta in Friesian mares after normal foalings, and with gestational length. The analysis was carried out using marginal logistic regression, and mixed linear regression, respectively. The incidence of retained placenta was 54%. Mean length of gestation was 331.6 days. Colts were carried 1.5 days longer than fillies. Mares bred in July-September had a 4-day shorter gestation period (329 days) than mares bred earlier in the year. There was a mare, sire, and dam's sire effect on gestational length, and a mare effect on the occurrence of retained placenta. Mares foaling at 4 and >17 years of age, tended to have a lower incidence of retained placenta than mares foaling at 5-17 years of age. No association was found between the occurrence of retained placenta, and gestational length, sex of the foal, month of breeding, dam's sire, and time of day of foaling. It was concluded that the observed high incidence of retained placenta indicates that the Friesian breed of horses has a higher risk for retained placenta than other breeds of horses.

Bile acids increase response and expression of human myometrial oxytocin receptor

OBJECTIVE

We tested the hypothesis that during intrahepatic cholestasis of pregnancy bile acids activate the myometrial oxytocin receptor pathway.

STUDY DESIGN

Myometrial sensitivity to oxytocin and oxytocin-receptor messenger RNA and protein level was investigated. The ability of cholic acid to mediate such changes was evaluated.

RESULTS

Cholestasis patients required lesser oxytocin to elicit four uterine contractions in 10 minutes (1.3+/-0.6 vs 3.6+/-0.8 U, P<.05, n=7) and had lower in vitro ED(50) (1.6 x 10(-10) mol/L vs 1.0 x 10(-8) mol/L, P<.05, n=7) than controls. The 24-hour incubation of control myometrial strips (n=7) with cholic acid (20 micromol/L) increased oxytocin sensitivity. Incubation of cultured myometrial cells (n=5) with cholic acid increased oxytocin-receptor expression (messenger RNA and protein).

CONCLUSION

We demonstrate that during intrahepatic cholestasis of pregnancy, an activation of the oxytocin receptor pathway occurs. This event seems to be the result of a cholic acid-mediated increase in oxytocin-receptor expression.

What have we learned about uterine contractions and preterm birth? The HUAM Prediction Study

Measurement of uterine contraction frequency has been employed as a screening test to identify women with increased risk of preterm birth, and as an aid in the early diagnosis of preterm labor. The National Institute of Child Health and Human Development Maternal-Fetal Medicine Units (NICHD MFMU) Network performed a prospective, blinded observational study of uterine contraction frequency to detect and predict preterm labor and birth, respectively. The goal of the study was to assess the sensitivity, specificity, and positive and negative predictive value of various measures of uterine contraction frequency. Data collected from 306 women revealed that contraction frequency was significantly greater in women who would ultimately deliver before rather than after 35 weeks' gestation. However, both sensitivity and positive predictive value of any measure of contraction frequency to predict preterm birth were poor. Contraction frequency did not increase significantly within 1 or 2 weeks of an episode of preterm labor. These results serve to explain the absence of an association between contraction-based surveillance and preterm birth in randomized trials conducted in women at risk of preterm birth.

The "Christmas Effect" and other biometeorologic influences on childbearing and the health of women

OBJECTIVE

To review the body of literature addressing biometeorologic and chronobiologic effects on conception, pregnancy, parturition, and other health conditions.

DATA SOURCES

Computerized searches of MEDLINE, PUBMED, CINAHL, and the World Wide Web.

STUDY SELECTION

Studies, including international research, dating from 1938 to 2001.

DATA EXTRACTION

Data were extracted and information organized under the following categories: influence of leisure time and seasonality on the rate of conception and birth, the relationship of meteorologic changes and lunar cycles to childbearing, the "Christmas Effect" and its impact on other health outcomes, and nursing implications.

DATA SYNTHESIS

Research from the disciplines of biometeorology and chronobiology indicates that there are patterns in the occurrence of conception, pregnancy, and onset of labor that vary in timing and amplitude in different populations and geographic regions. Consideration of these factors should be included in the analysis of birth data when planning and providing maternity care. The Christmas Effect is one of the most predominant seasonal patterns that can be seen in birth data throughout the world.

CONCLUSIONS

Biometeorologic and other cyclic phenomena are underused in the United States in planning and providing maternity care. These phenomena warrant consideration when planning holistic health care.

Frequency of uterine contractions and the risk of spontaneous preterm delivery

BACKGROUND

The measurement of the frequency of uterine contractions has not been useful for reducing the rate of preterm delivery in randomized trials. Nonetheless, ambulatory monitoring of contractions continues to be used in clinical practice.

METHODS

We assessed the frequency of uterine contractions as a predictor of the risk of spontaneous preterm delivery before 35 weeks of gestation. We enrolled women with singleton pregnancies between 22 and 24 weeks of gestation. The women used a contraction monitor at home to record contraction frequency twice daily on 2 or more days per week from enrollment to delivery or 37 weeks of gestation.

RESULTS

We obtained 34,908 hours of successful monitoring recordings from 306 women. Although more contractions were recorded from women who delivered before 35 weeks than from women who delivered at 35 weeks or later, we could identify no threshold frequency that effectively identified women who delivered preterm infants. The sensitivity and positive predictive value of a maximal hourly frequency of contractions of four or more between 4 p.m. and 3:59 a.m. were 9 percent and 25 percent, respectively, at 22 to 24 weeks and 28 percent and 23 percent at 27 to 28 weeks. Other proposed screening tests, such as digital and ultrasound evaluations of the cervix and assays for fetal fibronectin in cervicovaginal secretions, also had low sensitivity and positive predictive value for preterm labor.

CONCLUSIONS

Although the likelihood of preterm delivery increases with an increased frequency of uterine contractions, measurement of this frequency is not clinically useful for predicting preterm delivery.

The development of circadian rhythms in the fetus and neonate

The circadian time-keeping system is the neural system that allows predictive adaptation of individuals to the reproducible 24-hour day/night alternations of our planet. A biological clock, the suprachiasmatic nucleus, receives environmental information and imposes a circadian pattern to physiological functions. Since the suprachiasmatic nucleus develops early in gestation and circadian rhythms are present in the fetus and newborn, the circadian system seems to be functional in fetal life and can receive circadian inputs through the mother. The neonate moves to an environment in which the main time giving signal is the light:dark cycle. Teleologically, a term newborn should be fit to face this challenge. But this may be quite different for a preterm infant that trades the circadian environment to which it was previously exposed for the timeless environment of the Neonatal Intensive Care Nursery. Scientists and physicians should seek new experimental and clinical approaches to answer the challenging questions of perinatal chronomedicine.

Correlation of antepartum uterine activity and cervical change in twin gestation

OBJECTIVE

To determine the correlation between quantitative measurements of antepartum uterine activity and cervical change twin gestations.

METHODS

Forty women from our Twin Clinic constituted the study group. Participants had a cervical examination each week between 20 and 37 weeks gestation and a cervical score (CS) was calculated as follows: CS = cervical length (cms)-cervical dilation (cms) at the internal os. The women also performed blinded home uterine activity monitoring (HUAM) for a mean of 7.0 + 3.0 hrs/wk (+SD). Uterine activity was expressed as mean number of contractions/hour/week gestation based on the average of three independent reviewers. CS was determined by a single clinician unaware of the HUAM recordings. A significant change in the CS was defined as a reduction of at least 0.5 from the preceding week. Correlation coefficients were used to determine the association between uterine activity and change in the cervical score.

RESULTS

Twin pregnancy was characterized by a rise from 0.2 + .03 contractions/hr at 20 weeks to 3.2 + 2.4 contractions/hr at 37 weeks gestation. CS fell from a mean of 2.6 + 0.2 at 20 weeks to -2.1 + 0.9 at 37 weeks gestation. There was a significant negative correlation (-0.317, p < .0001) between increasing uterine activity and decreasing CS. There were significantly more (p < .002) contractions during the 7 days preceding a significant reduction in CS (3.3 + 3.5 contractions/hr) than when the CS was unchanged (1.6 +/- 1.5 contractions/hr).

CONCLUSIONS

In twin gestations, an increasing frequency of uterine contractions is strongly correlated with quantifiable cervical change between 20-37 weeks gestation. Persistent daytime contraction frequencies of > 3/hr represent a risk factor for cervical dilation and/or effacement.

Instrumentation for the diagnosis of term and preterm labour

The problems associated with labor during pregnancy are among the most important health issues facing physicians. Understanding the role of the uterus and cervix in labor and developing methods to control their function is essential to solving problems relating to labor. At the moment, only crude, inaccurate and subjective methods are used to assess changes in the uterus and cervix that occur in preparation for or during labor. In the past several years, we have developed noninvasive methods to quantitatively evaluate the uterus and cervix based respectively on recording of uterine electrical signals from the abdominal surface (uterine EMG) and measurement of light-induced cervical collagen fluorescence (LIF) with an optical device (Collascope). The methods are rapid and allow assessment of uterine contractility and cervical ripening. Studies in rats and humans indicate that uterine and cervical function can be successfully monitored during pregnancy using these approaches and that these techniques might be used in a variety of conditions associated with labor to better define management. The potential benefits of the proposed instrumentation and methods include a reducing the rate of preterm delivery, improving maternal and perinatal outcome, monitoring treatment, decreasing cesarean section rate and improving research methods to understand uterine and cervical function.

Antenatal patterns of uterine activity in low-risk women: a longitudinal study

There is a surprising lack of information on antenatal patterns of uterine activity in the normal obstetric population, with the majority of research having focussed on women at high-risk for preterm birth. We conducted a prospective longitudinal study to investigate patterns of uterine activity in women with singleton gestations at low-risk for preterm birth. Twenty pregnant women were recruited and their uterine activity was recorded using ambulatory tocodynamometry twice weekly throughout the latter half of pregnancy. The collected data were transmitted to a central receiving station for analysis. As gestation advanced there was a progressive increase in the median number of contractions detected per hour, peaking and stablizing at 37-40 weeks (median of 0 contractions/hour at 20-24 weeks rising to 5.4 contractions/hour at 37-40 weeks). In those women with uterine activity, contraction duration and amplitude of deflection significantly increased as gestation advanced. There was a progressive increase in the number of higher amplitude contractions throughout the third trimester. Increasing parity was not associated with increasing antenatal uterine contraction frequency. No association between normal daily physical activity and uterine contraction frequency was evident throughout gestation. In normal human pregnancy there is a steady, progressive increase in the frequency, duration and amplitude of antenatal uterine activity throughout the latter half of gestation. The uterine contractile profile alters from one of a low amplitude, low frequency pattern in the second trimester to a higher amplitude, higher frequency pattern at term.

A validation study of home uterine activity monitoring technology in Western Australia

Home uterine activity monitoring has been developed as an 'early warning' device to detect premature uterine activity, thereby encouraging earlier referral and tocolysis of women at risk of preterm delivery. This ambulatory monitoring system, utilizing a ring-guard tocodynamometer, was piloted in Western Australia to determine if it can reliably record and transmit antenatal uterine activity data in an Australian environment. Pregnant women were readily able to correctly apply and use the ambulatory monitoring device. The information collected was able to be transmitted using standard Australian telecommunications systems within our hospital environment. Validation studies with the ambulatory monitor and current external tocodynamometry hardware were performed. The ring-guard tocodynamometer detected more uterine activity at gestations less than 32 weeks compared with conventional external tocodynamometers. As term approached, however, the sensitivity of the ring-guard tocodynamometer decreased. A cross-sectional profile of antenatal uterine activity was developed for women at low risk of delivering preterm. A gradual increase in the number, duration and amplitude of uterine contractions as pregnancy advanced was observed.

Diurnal rhythms in cardiorespiratory function of the fetal baboon

Diurnal periodicities of cardiorespiratory function were monitored between 144 and 156 days of gestation (term = 175 days) in six chronically instrumented fetal baboons. For each fetus, 5-11 days of electrocardiographic and tracheal fluid pressure data were summarized as hourly means of fetal heart rate (FHR), standard deviation of FHR, breath-to-breath interval (B-Bi) and percent time spent in fetal breathing activity (PFB). Summaries were evaluated by cosinor analysis to determine the least squares fit to a 24-h cycle. For all fetuses, FHR had a significant (P < 0.001) diurnal rhythm with peak to nadir fluctuations of 17.4 beats/min around a 24-h mean of 163.2 beats/min. The time of the peak FHR was similar across animals occurring in the mid-day between 10:49 h and 14:45 h. For each fetus, standard deviation of FHR also had a significant (P < 0.01) diurnal periodicity with highest values at night between 20:15 h and 02:04 h. The times of the acrophase for these heart rate parameters were correlated (R = 0.88, P < 0.02) across fetuses. Significant (P < 0.001) 24-h rhythms were found in four of six fetuses for B-Bi and five of six for PFB. These PFB rhythms accounted for a fluctuation of 14.4% around a mean of 36.9 +/- 4.5%. In contrast to heart rate, the acrophases of fetal breathing parameters were distributed throughout the entire 24-h cycle and not significantly correlated across fetuses. It is concluded that diurnal rhythms of fetal heart rate, which are synchronized with light/dark conditions in the environment, are evidence for a passive response or entrainment of fetal systems to maternal circadian influences. Alternately, the absence of synchronization across fetuses in daily rhythms of fetal breathing activity provides evidence for a functioning fetal pacemaker, and not simply the imposition of maternal rhythms on her fetus. This differential in the cardiac and breathing activity of the developing primate indicates that pathways for entrainment of fetal pacemaker function are subject to important maturational influences during late gestation.

Perinatal development of human circadian rhythms

The early development of circadian rhythms in primates, including man, was reviewed. Continuous 24-h recordings were carried out for maternal and fetal circadian rhythms during gestation as well as in preterm infants. Several propositions were made based on these new findings: 1. The fetal biological clock is an endogenous clock capable of generating circadian rhythms and responding to maternal entraining signals long before the moment of birth. 2. Through the fetal biological clock, maternal circadian rhythms influence the fetal overt rhythms. 3. Maternal rhythms influence the fetus, and fetal rhythms feed back to the mother (via the placenta). Disruption of this fetal-maternal interaction during gestation leads to: a. disturbances of maternal and fetal circadian rhythms; b. disappearance of circadian rhythms at the time of birth; c. a gestational period which is either too short or too long (see also Honnebier and Swaab, 1973); d. delayed or impaired maturation of the circadian rhythms of the infant.

New perspectives for the effective treatment of preterm labor

Preterm birth (before 37 completed weeks of gestation) continues to account for the vast majority of neonatal morbidity and mortality. The incidence of preterm birth can be reduced by appropriate social interventions and antenatal care. Currently available tocolytic agents suffer from low uterospecificity and prolong pregnancy only marginally, although postponement of birth by a few days may be of some value. Further progress is needed in at least four areas: prevention of preterm labor; identification of preterm labor; selection of candidates for tocolysis, and treatment of preterm labor. Effective, early treatment of vaginosis offers particular promise for the prevention of preterm labor and identification of specific biochemical markers will facilitate early detection of this process. Oxytocin antagonists offer greater specificity than current tocolytics and can be expected to show improved efficacy and risk profiles. Such compounds will allow more effective treatment of preterm labor with a lower risk of side effects.

Endothelin-1 potentiates the in vitro contractile response of pregnant human myometrium to oxytocin

OBJECTIVE

This study was designed to test the hypothesis that endothelin-1 pretreatment of human myometrium at subcontractile doses in vitro will enhance the contractile response to oxytocin.

STUDY DESIGN

In vitro contractile oxytocin dose-response curves were generated by use of myometrial strips collected from nonpregnant women (n = 7), pregnant patients at elective cesarean section (n = 7), and patients in active labor (n = 7) in the presence or absence of 10(-9) mol/L endothelin-1. Contractile responses were analyzed by on-line computer, and data were normalized to the maximum response to potassium.

RESULTS

Pretreatment with endothelin-1 significantly increased the maximal contractile response of pregnant myometrium (p < 0.01 compared with control). In marked contrast myometrium from nonpregnant patients was unaffected by endothelin-1 pretreatment. Values for the two-point discrimination and Hill coefficient were not different among the treatment groups.

CONCLUSION

Endothelin-1 potentiates the oxytocin response of myometrium from pregnant but not nonpregnant women. We speculate that a high circulating level of a uterotonin-like oxytocin may not be necessary to initiate labor. The synergistic interaction between different uterotonins may be sufficient.

Cervical examination and tocodynamometry at 28 weeks' gestation: prediction of spontaneous preterm birth

OBJECTIVE

We determined the value of cervical examination and tocodynamometry in identifying nulliparous women at risk for spontaneous preterm delivery.

STUDY DESIGN

At 27.5 +/- 0.8 weeks' gestation 589 women underwent 30 minutes of tocodynamometry, and 570 of these had a cervical examination. Positive findings on these examinations were compared to the rate of spontaneous preterm delivery, defined as those deliveries following the onset of spontaneous labor or premature rupture of membranes.

RESULTS

The two best predictors of spontaneous preterm birth were two or more contractions in 30 minutes and the presence of a soft or medium consistency on cervical examination. As the contractions increased from zero to four or more, the rate of spontaneous preterm delivery rose from 4.2% to 18.2%.

CONCLUSION

In nulliparous women at 28 weeks' gestation, uterine contractions and several components of the cervical examination predicted spontaneous preterm birth.