Measuring fetal and maternal temperature differentials: a probe for clinical use during labour

The healthy fetus maintains a higher temperature than that of its mother during gestation and labour. This results from the thermal balance between the heat generated by the fetus and the heat loss to its maternal surroundings. The heat loss can be by heat exchange via blood flowing in the umbilical cord and placenta, and via conduction through the fetal skin and amniotic fluid to the maternal wall. The temperature difference between the fetal and maternal tissue may reflect the metabolic state of the fetus and the magnitude and changing patterns of placental blood flow during labour. Physiological changes, such as those induced by epidural analgesia, and fetal infection have been shown to exhibit an increase in the absolute temperature. An intrauterine probe, previously used for non-invasive ECG detection, has been equipped with temperature sensors that measure fetal and maternal skin temperature in utero. Laboratory tests to characterize the performance of the probe reveal that absolute and differential temperatures can be resolved to around 0.01° C with a thermal time constant of approximately 9 s. Ideally the probe body should have infinite thermal insulation or thermal shunting across the probe will occur reducing the measured temperature difference. In this initial probe design, a high thermal isolation between sensors has been achieved but is not perfect, resulting in around 85% of the actual temperature difference across the probe being registered. Average feto-maternal differences of 0.2° C have been measured in a clinical investigation.     

Fetal ECG during labour: a suggested standard

Recording the fetal ECG as a means of fetal monitoring during labour has been investigated by many researchers. Different signal processing methods have been used, making comparisons difficult so that agreement on several topics has not been reached. We suggest the basis of a standard method of recording and processing the signal which we believe will be acceptable to the research and clinical communities.     

Properties of fetal heartbeat intervals during labour

This study was designed to investigate the range of beat-to-beat changes in fetal inter-beat (RR) intervals during routine clinical monitoring in labour. Fetal RR intervals were automatically measured and collected from 10 fetuses. Intervals which were incorrectly measured were excluded, and the remaining 23510 intervals were used to compile the distribution of beat-to-beat changes. The inter-quartile range of this distribution was 23 ms and the 99th centile fell at approximately 50 ms. No relationship could be established between beat-to-beat changes and the absolute RR interval. These findings differ from the results published by other workers on the basis of data obtained antenatally or during early labour. In addition, the results suggest possibilities for improving algorithms designed to enhance data quality in fetal heart rate monitoring.     

Fetal ECG during labour: a presentation of a microprocessor system

Changes in the ST waveform of the fetal ECG have been detected in 47 term deliveries with vertex presentations using a specially developed microprocessor-based system for on-line recording of T wave amplitude. The T wave was quantified by the T/QRS ratio. The recording included one scalp electrode for exploration and a maternal skin electrode as reference. Signal quality allowed optimal ST waveform assessment in 89% of the cases. The degree of perinatal asphyxia was judged from cord artery acid-base status and the neonatal outcome. In completely normal fetuses at term the mean T/QRS ratio was 0.148 with a standard deviation of 0.048. With this basic information we can proceed in the investigation of the T/QRS ratio as a means for fetal surveillance.     

Induction of labour with prostaglandin E2 gel in cases of intrauterine fetal death.

In established intrauterine fetal death, 20 patients were treated with prostaglandin E2 gel administered extraamniotically. The results were compared with those of another group of 20 patients who had received combined treatment. In this group, one or more of the following agents had been administered :- i.v. oxytocin, 20% NaCl solution or Premarin instilled intraamniotically, introduction of a balloon catheter or Rivanol administered extraamniotically. Average induction-abortion interval for the PG group was about 12 hours while for the second group it was about 30 hours. The side effects observed were slight in both groups. The results show that administration of PG-gel can be used with advantage in fetal demise because of the relatively short induction-abortion intervals obtained, the insignificant side effects and the low dose of PG required.     

Changes of maternal and fetal pituitary-adrenocortical functions during human labour

The results of maternal 11-hydroxycorticoid (11-OHCS) determination on blood obtained from four stages of 44 spontaneous labour cases showed a strong and time-related maternal adrenocortical activation during vaginal delivery. The high 11-OHCS level in the cord blood and the increase of the 11-OHCS concentration in the amniotic fluid suggested the same response of the fetal adrenal. However, in 14 cases of elective caesarean sections the 11-OHCS levels in the cord blood and the amniotic fluid did not rise in spite of the elevated maternal plasma 11-OHCS content.     

Induction of labour with prostaglandin E2 gel in cases of intrauterine fetal death

In established intrauterine fetal death, 20 patients were treated with prostaglandin E₂ gel administered extraamniotically. The results were compared with those of another group of 20 patients who had received combined treatment. In this group, one or more of the following agents had been administered: - i.v. oxytocin, 20% NaCl solution or Premarin instilled intraamniotically, introduction of a balloon catheter or Rivanol administered extraamniotically. Average induction-abortion interval for the PG group was about 12 hours while for the second group it was about 30 hours. The side effects observed were slight in both groups. The results show that administration of PG-gel can be used with advantage in fetal demise because of the relatively short induction-abortion intervals obtained, the insignificant side effects and the low dose of PG required.     

心电信号特征量的小波提取算法

目的:为了更准确地利用心电图(ECG)进行临床生理疾病诊断,提高心电信号的自动分析准确度.介绍了一种利用小波变换的时频局部化特性以及多分辨率特性对心电信号进行处理的算法.方法:使用定位准确.计算简便的二阶微分Mart小波使用多孔算法来对ECG中QRS波群进行标定.结果:将算法应用到MIT/BIH国际标准心电数据库进行仿真.结论:通过仿真证明,该算法能够很精确地定位QRS波群,为心电信号的后续研究打好基础.     

Changes in fetal organ flow during intrauterine mechanical ventilation with or without oxygen

To investigate whether the changes in circulation at birth are due to lung ventilation, changes in PaO2 or both we mechanically ventilated in utero the lungs of 10 fetal sheep (120-127 days of gestational age) five days after instrumentation under general anaesthesia. Electrocortical activity (ECoG), eye movements (EOG), electromyographic activity from diaphragm and posterior neck activity (EMG) and electrocardiogram (ECG) were recorded. Fetal catheters (artery and vein of the hindlimb, arteries of both forelimbs which in three occasions were advanced into the left ventricle, fetal trachea and amniotic cavity), and an endotracheal tube were placed. After recovery radioactive 15 mu microspheres (I125, Ce141, Sr85 and Sc46) were injected into the inferior vena cava or left ventricle during high voltage electrocortical activity before and after lung expansion with N2 and after expansion with O2 for two levels of PaO2. PaCO2 did not change. The percentage of spheres trapped in the lungs increased from 9.6% to 44% after expanding the lungs with N2 and to 90% when fetal PaO2 increased (P less than 0.001). Blood flow to different organs did not change during normoxic expansion but it decreased significantly to the brain (91 +/- 25 to 27 +/- 8 ml/min per 100g, [mean +/- SD]) placenta (160 +/- 57 to 54 +/- 33 ml/min/100g) and coronaries (239 +/- 91 to 117 +/- 60 ml/min per 100g) when PaO2 was increased. In conclusion fetal circulation responds to raised levels of PaO2 well before birth probably by a direct action of oxygen on the vessels.     

Enzyme immunoassay of oestrogen and progesterone receptors in uterine and intrauterine tissue during human pregnancy and labour

Oestrogen and progesterone receptors were studied in the non-pregnant state, in early pregnancy and at term using monoclonal antibody enzyme immunoassays. Receptors for both steroids were found in tissues from non-pregnant patients and patients in early pregnancy. At term oestrogen receptors were undetectable in all tissues studied. Progesterone receptors were undetectable in chorion, amnion and placenta at term, while present in extremely low concentrations in decidua and myometrium.     

Concentration of oxytocin receptors in the placenta and fetal membranes of cows during pregnancy and labour.

The concentrations of oxytocin receptors were measured in intercaruncular and caruncular endometrium, fetal cotyledons, chorioallantois and amnion during pregnancy and parturition in cows. Tissues were obtained on days 20 (endometrium only), 50, 100, 150, 200, 225, 250, 275, at term (days 280-284), during labour and within 24 h after calving. Receptor concentrations in intercaruncular endometrium were low on day 20 of pregnancy, 39 +/- 11 fmol mg-1 protein. By day 50, receptor concentrations had increased more than tenfold to 572 +/- 52 fmol and rose steadily until day 250 and then levelled off at about 4500 fmol mg-1. Shortly before parturition, on day 282 +/- 1, a further rise to 7300 +/- 1418 fmol mg-1 was observed, these concentrations were maintained throughout labour. By contrast, caruncular endometrial receptor concentrations remained low until term, mean 145 +/- 15 fmol mg-1, and then rose to 720 +/- 163 fmol mg-1 during labour (cervix 17 cm--fully dilated). Fetal cotyledons and membranes had very low oxytocin receptor concentrations during most of pregnancy, on average only 20 fmol mg-1 protein. At term and during labour, receptor concentrations were significantly increased in both tissues. Mean concentrations during labour were 163 +/- 36 fmol mg-1 for cotyledons, 270 +/- 61 fmol mg-1 for chorioallantois and 311 +/- 121 fmol mg-1 for amnion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Craniosynostosis and altered patterns of fetal TGF-beta expression induced by intrauterine constraint

Recent work has demonstrated that fusion of the calvarial sutures is mediated by locally elaborated soluble growth factors, including the transforming growth factor-betas (TGF-betas), leading some to speculate that external biomechanical forces play little role in suture development. Clinical evidence has long suggested, however, that fetal head constraint may play a critical role in the pathogenesis of many cases of nonsyndromic craniosynostosis. The purpose of these experiments was to test the hypothesis that intrauterine constraint leads to an alteration in normal patterns of TGF-beta expression and that these alterations are associated with craniosynostosis. Fetal constraint was induced by allowing C57Bl/6 murine fetuses to grow for 2.5 days beyond the normal 20-day gestation by performing uterine cerclage on the eighteenth day. Cranial suture morphology was examined in hematoxylin and eosin-stained sections and in cleared whole-mount specimens, double stained with alizarin red S and Alcian blue. Expression patterns of TGF-beta1 and TGF-beta3 were examined by immunohistochemical techniques. Gross and microscopic examination of the cranial sutures of 17 constrained fetuses revealed changes that ranged from narrowing to complete osseous obliteration of the coronal and squamosal sutures. All sutures of 14 nonconstrained control pups remained patent. Fetal head constraint was associated with increased TGF-beta1 immunoreactivity within the new bone and the underlying dura when compared with nonconstrained age-matched controls. TGF-beta3 immunoreactivity was associated with the dura underlying patent, nonconstrained sutures, whereas constraint-induced synostosis was characterized by down-regulation of dural TGF-beta3 expression. These experiments confirm the ability of intrauterine constraint to induce premature fusion of the cranial sutures and provide evidence that intrauterine head constraint induces the expression of osteogenic growth factors in fetal calvarial bone and the underlying dura.     

Prostaglandins mediate the fetal pulmonary response to intrauterine inflammation

Intra-amniotic (IA) lipopolysaccharide (LPS) induces intrauterine and fetal lung inflammation and increases lung surfactant and compliance in preterm sheep; however, the mechanisms are unknown. Prostaglandins (PGs) are inflammatory mediators, and PGE(2) has established roles in fetal lung surfactant production. The aim of our first study was to determine PGE(2) concentrations in response to IA LPS and pulmonary gene expression for PG synthetic [prostaglandin H synthase-2 (PGHS-2) and PGE synthase (PGES)] and PG-metabolizing [prostaglandin dehydrogenase (PGDH)] enzymes and PGE(2) receptors. Our second study aimed to block LPS-induced increases in PGE(2) with a PGHS-2 inhibitor (nimesulide) and determine lung inflammation and surfactant protein mRNA expression. Pregnant ewes received an IA saline or LPS injection at 118 days of gestation. In study 1, fetal plasma and amniotic fluid were sampled before and at 2, 4, 6, 12, and 24 h after injection and then daily, and fetuses were delivered 2 or 7 days later. Amniotic fluid PGE(2) concentrations increased (P < 0.05) 12 h and 3-6 days after LPS. Fetal lung PGHS-2 mRNA and PGES mRNA increased 2 (P = 0.0084) and 7 (P = 0.014) days after LPS, respectively. In study 2, maternal intravenous nimesulide or vehicle infusion began immediately before LPS or saline injection and continued until delivery 2 days later. Nimesulide inhibited LPS-induced increases in PGE(2) and decreased fetal lung IL-1β and IL-8 mRNA (P ≤ 0.002) without altering lung inflammatory cell infiltration. Nimesulide decreased surfactant protein (SP)-A (P = 0.05), -B (P = 0.05), and -D (P = 0.0015) but increased SP-C mRNA (P = 0.023). Thus PGHS-2 mediates, at least in part, fetal pulmonary responses to inflammation.     

Detection and prevention of premature labour

Preterm birth is a major public health problem, affecting up to 10% of pregnancies. The cause of premature labour in humans is not known, although some risk factors have been identified. Currently it is not possible to predict which women will go into labour prematurely or deliver preterm. New possible methods for the detection of premature labour are the measurement of biochemical markers in cervical or vaginal secretions, the measurement of collagen in cervical tissue and the recording of electrical properties of contractions of the uterus. Agents used to prevent premature labour include beta-agonist drugs, magnesium sulphate, calcium channel blockers, nitric oxide donors and prostaglandin synthesis inhibitors. A new approach is the use of oxytocin antagonists. Premature labour is still not completely understood, but some advances are being made, arising from basic research.     

The relationship between fetal breathing movements and prostaglandin E2 during ACTH-induced labour in sheep

We measured fetal breathing movements and fetal carotid arterial prostaglandin E concentrations during adrenocorticotrophin-induced labour in 6 pregnant sheep and in 6 control animals starting at day 127. The 6 ACTH-treated animals went into labour on average 97 h after the onset of infusion and the incidence of fetal breathing movements diminished during the last 12h before the onset of labour. There was a significant negative relationship between the incidence of fetal breathing movements and fetal carotid arterial prostaglandin E concentrations (r = -0.88; P less than 0.001) in ACTH treated animals. These data suggest a role for prostaglandin E in the diminution of fetal breathing movements prior to the onset of labour.     

Continuous fetal monitoring in the ambulant patient in labour.

Fetal heart rate was monitored continuously in 30 ambulant women in labour by radiotelemetry. The procedure was practicable and, since contractions were less uncomfortable with the patient standing or walking about, reduced the need for analgesia. It also resulted in a more natural labour. Use of the procedure may lessen the risk of thromboembolism.