Qualitative assessment of maternal uterine and fetal umbilical artery blood flow and resistance in laboring patients by Doppler velocimetry

Brar, Harbinder S.; Platt, Lawrence D.; DeVore, Greggory R.; Horenstein, Janet; Medearis, Arnold L.

doi:10.1016/0002-9378(88)90100-7

Cited by 116 publications

(75 citation statements)

References 10 publications

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“…In addition, fetal lamb temperature increases before lambing and decreases approximately 1.5°C within 20 min after lambing, even in a temperature-controlled environment [16], indicating that this mechanism may protect newborn lambs from hyperthermia. Furthermore, one study reported that fetal temperature continues to increase through parturition because myometrial contractions also decrease uterine blood flow and heat dissipation by the fetus [1]. The results of the present study suggested that similar mechanisms may also occur in horses.…”

Section: Discussionsupporting

confidence: 55%

Assessment for Predicting Parturition in Mares Based on Prepartum Temperature Changes Using a Digital Rectal Thermometer and Microchip Transponder Thermometry Device

et al. 2012

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ABSTRACT. The purpose of this study was to observe the changes in body temperature before parturition using a wireless temperature monitoring device (WTMD) and to evaluate the usefulness of body temperature measurements using a digital rectal thermometer (DRT) and a microchip transponder thermometry device (MTTD) for predicting parturition in mares. The body temperatures using a WTMD at 0 hr and −1 hr were significantly different from those at the same time on Days 1-5 (P<0.01). The temperature differences between the morning of Day 0 and at −3 hr, −2 hr, −1 hr and 0 hr using the DRT and MTTD showed a significant drop compared with the temperature differences between the morning and evening of Days 1-5 (P<0.05). Furthermore, when the cutoff value of the temperature differences between the morning and other times was set to ≤0, the sensitivities of the DRT and MTTD in the evening of Day 0 and at −3 hr were 43% and 100% and 71% and 86%, respectively. The results suggested that monitoring the body temperature differences between morning and within 3 hr before the time of parturition is a valuable method for predicting parturition in mares. Conversely, this method would be more useful in predicting parturition when used in combination with other observations such as the mammary gland size and waxing of the teat ends because it has nearly a 20% probability of false-positive results prior to the day of parturition. KEY WORDS: body temperature, equine, microchip transponder thermometry device, predicting parturition.

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Section: Discussionsupporting

confidence: 55%

Assessment for Predicting Parturition in Mares Based on Prepartum Temperature Changes Using a Digital Rectal Thermometer and Microchip Transponder Thermometry Device

et al. 2012

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“…Thus, in this experimental set-up, hypoxia was induced by superfusing the tissue with the hypoxic solution and simultaneous bubbling of N 2 into the bath chamber for at least 10 min. Measurements of pO 2 showed values of 5% were obtained in these experiments.…”

Section: Methodsmentioning

confidence: 95%

“…A puzzling feature of labor is that contractions become progressively stronger as the myometrium (uterine muscle) experiences repetitive metabolic stress from hypoxia. This reaction occurs because as contractions develop they briefly compress the uterine blood vessels (2,3). Transient decreases of oxygenation, pH, and ATP, all of which if sustained can decrease contractile activity, occur in vivo with each contraction (3)(4)(5).…”

mentioning

confidence: 99%

Hypoxia-induced force increase (HIFI) is a novel mechanism underlying the strengthening of labor contractions, produced by hypoxic stresses

Alotaibi

Arrowsmith

Wray

2015

Proc. Natl. Acad. Sci. U.S.A.

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For successful birth, contractions need to become progressively stronger. The underlying mechanisms are unknown, however. We have found that a novel mechanism, hypoxia-induced force increase (HIFI), is switched on selectively, at term, and is essential to strengthening contractions. HIFI is initiated as contractions cyclically reduce blood flow and produce repeated hypoxic stresses, with associated metabolic and transcriptomic changes. The increases in contractility are a long-lasting, oxytocin-independent, intrinsic mechanism present only in the full-term pregnant uterus. HIFI is inhibited by adenosine receptor antagonism and blockade of cyclooxygenase-2 signaling, and partially reproduced by brief episodes of acidic (but not alkalotic) pH. HIFI explains how labor can progress despite paradoxical metabolic challenge, and provides a new mechanistic target for the 1 in 10 women suffering dysfunctional labor because of poor contractions. myometrium | smooth muscle | pH | hypoxia | hypoxic preconditioning P ulsatile releases of oxytocin are important for labor, but as oxytocin knockout mice deliver normally (1), other mechanisms for increasing contractile strength must occur. A puzzling feature of labor is that contractions become progressively stronger as the myometrium (uterine muscle) experiences repetitive metabolic stress from hypoxia. This reaction occurs because as contractions develop they briefly compress the uterine blood vessels (2, 3). Transient decreases of oxygenation, pH, and ATP, all of which if sustained can decrease contractile activity, occur in vivo with each contraction (3-5). Hypoxia regulates a large number of genes, including those governing metabolism and function in many tissues, and changes in genes associated with hypoxia have been identified as key findings in transcriptomic studies of poorly laboring women (6, 7). Chaemsaithong et al. and Mittal et al. confirmed changes in hypoxia-inducible factor 1a (HIF1a) using RT-PCR, as well as overexpression of cyclooxygenase-2 (COX2) in myometrium and endothelial NOS, which is important for blood vessel dilation. There is, however, no empirical evidence showing how such changes could be important to successful labors, and no existing mechanism linking hypoxia to an increase in contractions. In contrast, studies of hypoxia in myometrium and other smooth muscles show it to decrease contractility (8, 9).Of note, however, are studies demonstrating ischemic tolerance as an adaptive response initiated by several exposures to a stressor of mild severity, from which resistance to ischemia is markedly increased. This is known as hypoxic or ischemic preconditioning, and has been best investigated in cardiac muscle (10) and brain (11), where it is considered to be a powerful mechanism for limiting ischemic damage. Given that physiological decreases in oxygenation are part of the normal process of labor (4, 12), this finding therefore raised some important questions: What is the effect of brief but repetitive periods of hypoxia on uterine contractility? And...

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“…We also speculate that the decrease in maternal body temperature before parturition may be biologically important for decreasing uterine blood flow and heat dissipation by the fetus, resulting in an increased fetal temperature. Brar et al [16] found that fetal temperature continues to increase t h r o u g h p a r t u r i t i o n b e c a u s e m y o m e t r i a l contractions also decreased uterine blood flow and heat dissipation by the fetus. They hypothesize that the increase in fetal temperature before parturition may be an important compensatory mechanism for the loss in body temperature that occurs in newborns after delivery.…”

Section: Discussionmentioning

confidence: 99%

Body Temperature and Circulating Progesterone Levels before and after Parturition in Killer Whales (Orcinus orca)

et al. 2006

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Abstract. Killer whales were used to evaluate peripartum changes and interactions between body temperature and circulating progesterone concentration. Daily body temperature was measured between 0800 h and 0830 h before activity. Body temperature clearly increased during the first phase of pregnancy, and this was followed by a gradual decline until full term. The initial increase was paralleled by circulating levels of progesterone. A decrease in body temperature was first detected on day 5 (p<0.01) before parturition, and body temperature decreased significantly every 2 days until delivery. Five days before delivery, body temperature was 0.3 C lower than the mean value during the pregnancy period, and the decrease was more marked on day 1 before delivery (0.8 C). Serum progesterone levels during pregnancy showed a general pattern of initial rapid elevation (increasing phase), followed by a gradual decline (decreasing phase) throughout the remainder of pregnancy. However, statistically significant correlations between body temperature and progesterone pattern were only found only during the increasing phase. These results suggest that monitoring body temperature variation can be considered valuable for predicting impending parturition in killer whales.

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Qualitative assessment of maternal uterine and fetal umbilical artery blood flow and resistance in laboring patients by Doppler velocimetry

Cited by 116 publications

References 10 publications

Assessment for Predicting Parturition in Mares Based on Prepartum Temperature Changes Using a Digital Rectal Thermometer and Microchip Transponder Thermometry Device

Assessment for Predicting Parturition in Mares Based on Prepartum Temperature Changes Using a Digital Rectal Thermometer and Microchip Transponder Thermometry Device

Hypoxia-induced force increase (HIFI) is a novel mechanism underlying the strengthening of labor contractions, produced by hypoxic stresses

Body Temperature and Circulating Progesterone Levels before and after Parturition in Killer Whales (Orcinus orca)

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