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The feasibility of detecting the fetal ECG (FECG) from within the uterus in labour by a technique which is non-invasive to the fetus, has been investigated. The design of a special multi-electrode flexible probe has demonstrated that the FECG can be obtained with signal amplitudes of 20-300 microV and a success rate similar to that of the scalp electrode. Under favourable conditions very large signals can be detected in utero compared to a scalp electrode, but average signal amplitudes are lower. The probe is suitable as a carrier for other sensors such as pressure and temperature transducers. Currently, simultaneous FECG and intrauterine pressure measurement using a commercially available transducer within the same probe has been achieved.

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.

Uterine activity was measured in 60 women whose first labour was progressing slowly in the active phase. The mean level of active contraction area (uterine activity integral, UAI) before oxytocin augmentation was 898 (SD 458) kPas/15 min. UAI increased significantly with time, even in women not given oxytocin. UAI increased logarithmically with increasing oxytocin infusion rate. Levels of uterine activity before and after oxytocin infusion are correlated positively such that the higher the initial level of UAI the higher the UAI in response to oxytocin. However, the regression line approaches the line of identity such that even with high doses of oxytocin UAI would not be likely to exceed 2500 kPas/15 min. There is a positive correlation between uterine activity and cervical dilatation rate in unstimulated labour; however, this is less evident following oxytocin infusion. Increases in uterine activity below 1200 kPas/15 min result from both higher frequency and active pressure, whereas above 1200 kPas/15 min any increase is due mainly to a rise in frequency.

The involvement of phosphoinositide hydrolysis in the action of oxytocin and vasopressin on the uterus was investigated in gestational myometrium and decidua cells by measuring the production of inositol phosphates. Both peptides stimulated a dose related increase in all three inositol phosphates in myometrium. This may be related to the control of sarcoplasmic Ca++ levels in the myometrium. Oxytocin and vasopressin also stimulated inositol 1-phosphate (IP) production in decidua cells. The hydrolysis of phosphatidylinositol by decidua homogenates exhibited a precursor-product relationship for diacylglycerol and arachidonic acid accumulation. Hence both peptides may mobilise free arachidonic acid, for prostaglandin biosynthesis, from decidua cell phosphoinositides by the sequential action of phospholipase C and diacylglycerol lipase.

To establish the effect of pain relief on maternal temperature during labour forty patients who went into spontaneous labour with a single fetus, had a normal temperature (less than 37.5 degrees C), and had no clinical evidence of infection were investigated prospectively. They were divided into two comparable groups--one receiving pethidine and the other epidural analgesia. Both groups had much the same temperatures at the beginning of labour and before any analgesic administration. The mean temperature in the pethidine group remained constant during labour, whereas in the epidural analgesia group it showed a significant rise after only 6 hours of labour. This rise was not related to any clinical evidence of infection. Patients receiving epidural analgesia during labour are at increased risk of developing pyrexia. This pyrexia may be the result of vascular and thermoregulatory modifications induced by epidural analgesia.

A consecutive series of 56 infants of 32 weeks gestation or more who were resuscitated at birth by endotracheal intubation was studied to determine the occurrence of abnormal cardiotocograph traces and acidosis as determined by cord artery blood measurements. Thirty-two infants (57%) had neither cardiotocographic abnormalities nor acidosis; in this group the factors associated with the need for intubation were meconium stained amniotic fluid, operative delivery, anaesthetic agents given to the mother, a tight nuchal cord, and traumatic vaginal delivery. The need for intubation at birth should not automatically be regarded as evidence of intrapartum hypoxia or disturbed acid-base balance.

A microcomputer system is described which stores data for perinatal audit and produces 'on-line' the statutory birth notification form and mother and baby discharge summary. The derivation of a minimum data-base and the methods used to obtain reliable data are outlined. The results of a trial of the production of the birth notification form for 195 deliveries are reported together with those of a further trial of 86 deliveries in which the system was used to produce both the notification form and the discharge summary. A study of the accuracy of the handwritten birth notification forms revealed a high error rate which was markedly reduced by the use of the microcomputer system. The system is now in routine use and further developments are outlined.

The disadvantages of the fluid filled polythene catheter used for measuring intrauterine pressure have been overcome by designing a catheter with a pressure transducer at the tip. The information which it gives is accurate and reliable. The optimum method of use has been determined and clinical trials performed. There is no demonstrable morbidity from its use.

A simple electronic system for quantifying uterine activity in labour has been developed. The basic construction of the system is described. It has been used to confirm the hypothesis of Steer et al (1975) that oxytocin-induced labour has a stable phase during which uterine activity is largely independent of oxytocin infusion rate.

A detailed study has been made of uterine activity in a group of 21 unselected women in spontaneous labour. Measurements were made of contraction frequency, active pressure, Montevideo units and active contraction area. The level of Montevideo units were comparable with values previously reported in spontaneous labour. Active contraction area correlated better than any of the other measures with the rate of cervical dilatation in the active phase of labour (r = 0.69). The mean contraction area was 1099 (SD 333) kPas/15 min.

Continuous tissue pH and intermittent central arterial pH were measured in six rabbits during 10-min exposures to a mixture of 10% CO2 and 90% O2. In control and recovery situations tissue pH was more acidic than arterial pH by a mean value of 0.07 pH units. During periods of rapidly increasing pCO2, the steady state relationship was inverted with tissue pH being more alkaline than arterial pH. After a second exposure to CO2, mean tissue pH values did not recover to baseline. It is concluded that in the rabbit during acute hypercarbia, the relationship of tissue to central pH is variable. The possible implications of these results in human fetuses during labor are discussed.

A prospective study of the relationships among fetal heart rate pattern, meconium staining of the amniotic fluid, umbilical cord artery pH, and Apgar score was carried out in 1219 consecutive births. Interpretable cardiotocogram patterns and cord arterial pH and blood gas analysis were obtained in 698 cases. The sensitivity of an abnormal cardiotocogram at any time for acidosis (more than 1 SD below the mean, pH less than 7.17) was 80%, and for severe acidosis (more than 2 SDs below the mean, pH less than 7.085) was 83%. However, the predictive value was low, and 32% of fetuses had an abnormal cardiotocogram but no acidosis. If only cardiotocogram abnormality in the first stage of labor was considered, sensitivity was still 47% for acidosis and 67% for severe acidosis, and the false-positive rate was reduced to only 14%. We attempted to improve the prediction of acidosis by including meconium staining of the amniotic fluid, but 65% of the variation in umbilical cord artery pH and 72 and 86% of the variation in 1- and 5-minute Apgar scores, respectively, remained unexplained. In light of these poor correlations, the current practice of considering cardiotocogram abnormality, meconium staining of the amniotic fluid, acidosis, and low Apgar scores as indicating one single disorder, "fetal distress," is not valid.

Low maternal weight before pregnancy and poor weight gain during pregnancy are known to result in an increased prevalence of low birthweight infants. Low body weight is also an important cause of amenorrhoea. The hypothesis that amenorrhoeic underweight women who become pregnant after induction of ovulation are more at risk of delivering low birthweight infants than underweight women who ovulate spontaneously was investigated. Forty one pregnant women in whom ovulation had been induced and 1212 in whom ovulation was spontaneous were studied. Women ovulating spontaneously whose weight was normal and who showed good weight gain during pregnancy (greater than 450 g a week) had the lowest incidence (6%) of babies who were small for gestational age. Underweight women (body mass index less than 19.1) who ovulated spontaneously had a threefold increased risk of delivering babies who were small for gestational age (18%). Overall, the women in whom ovulation had been induced had an even higher risk of babies who were small for dates (25%), and the risk was greatest (54%) in those who were underweight. The outcome of pregnancy is related to weight before conception, which in many cases reflects nutritional state; lack of spontaneous ovulation indicates an increased risk of producing a small for dates infant. The most suitable treatment for infertility secondary to weight related amenorrhoea is therefore dietary rather than induction of ovulation.

It has been suggested that monitoring of uterine activity by placement of intrauterine catheters can cause an increase in maternal and fetal infection. The ways in which intrauterine catheters could transmit infection have been investigated. The risk of infection occurs primarily during placement of the catheter, although a risk also exists if bacterial nutrients are present in the fluid filling the catheter. Recommendations are made to minimize these risks.

A system for the online quantitation of uterine activity has been used to define the optimum levels and patterns of uterine activity in spontaneous labors and labors induced by oxytocin infusion. Using these parameters, the system automatically adjusts oxytocin infusion to suit the individual requirements of the patient. The infusion rate is subsequently automatically adjusted to take account of any increase or decrease in the uterine activity.

The influence of the state of the membranes on the fetal heart rate was studied in a group of twelve women whose membranes were electively ruptured for oxytocin induction of labour. The results have been compared with a group of eight women of similar gestation and parity whose membranes were kept intact. While membranes were ruptured, there was an increase in the frequency and amplitude of early decelerations thorughout labour. The significance and practical implications of the results are discussed.

Sixty women who were progressing slowly in spontaneous labour were assigned at random to three management protocols. Group 1 were observed without the use of oxytocin for 8 h while groups 2 and 3 were managed with a low-dose and high-dose oxytocin protocol respectively. The caesarean section rates were not significantly different between the three groups: 45%, 35% and 26% respectively. Cervical dilatation rate increased significantly after oxytocin infusion in both treatment groups compared with controls. The 'delay-to-delivery' interval and second stage duration were significantly shorter in the high-dose group than in the control group. There were no measurable differences in the condition of the newborn infants between the three groups.

The main indication for Caesarean section in cases of placental abruption is fetal distress. We report a patient in whom clinical examination, including auscultation of the fetal heart, suggested a mild haemorrhage, which would normally have been managed conservatively, but continuous fetal heart rate monitoring showed severe asphyxia, necessitating emergency Caesarean section at which a large concealed haemorrhage was found.

A study was made of the characteristics of oxytocin-induced labour. Twelve patients with, and eight without membrane rupture were closely matched for factors likely to influence the character and duration of labour. In both groups uterine activity increased until a stable state was achieved loowing which there was little alteration until delviery. The duration of labour was shorten in the group with ruptured membranes as compared with intact membranes although, paradoxically, the uterineactivity tended to be greater when the membranes were intact.

A randomized prospective controlled trial of an automatic feed-back controlled oxytocin infusion system (AIS) for the induction of labour at term was carried out in three hospitals. In primiparae, a four-fold reduction in the total dose of oxytocin infused, for the same induction-delivery interval, was achieved with the AIS compared with standard labour ward protocols relying on midwife control of oxytocin infusion rate. In multiparae, the total dose of oxytocin infused was almost halved when the AIS was used, while the mean duration of labour was increased by 1.6 h to 7.5 h. There were no differences in the mode of delivery or Apgar scores. It is concluded that the AIS is a safe technique for induction of labour. Its use has demonstrated that term labour can be induced efficiently with a mean oxytocin infusion rate between 2.5 and 3 mU/min (max 8.8 mU/min) and a total oxytocin dose infused of less than 5 U.

Vasopressin and oxytocin both stimulated inositol phosphate accumulation in isolated uterine decidua cells. Pretreatment of cells with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) prevented this agonist-induced phosphoinositide hydrolysis. TPA (0.1 microM) alone had no effect on basal inositol phosphate accumulation, but stimulated phosphoinositide deacylation, as indicated by a 2-fold increase in lysophosphatidylinositol and glycerophosphoinositol. TPA also stimulated a dose-related release of arachidonic acid from decidua-cell phospholipid [phosphatidylcholine (PC) much greater than phosphatidylinositol (PI) greater than phosphatidylethanolamine]. The phorbol ester 4 beta-phorbol 12,13-diacetate (PDA) at 0.1 microM had no effect on arachidonic acid mobilization. The TPA-stimulated increase in arachidonic acid release was apparent by 2 1/2 min (116% of control), maximal after 20 min (283% of control), and remained around this value (306% of control) after 120 min incubation. TPA also stimulated significant increases in 1,2-diacylglycerol and monoacylglycerol production at 20 and 120 min. Although the temporal increases in arachidonic acid and monoacylglycerol accumulation in the presence of TPA continued up to 120 min, that of 1,2-diacylglycerol declined after 20 min. In decidua cells prelabelled with [3H]choline, TPA also stimulated a significant decrease in radiolabelled PC after 20 min, which was accompanied by an increased release of water-soluble metabolites into the medium. Most of the radioactivity in the extracellular pool was associated with choline, whereas the main cellular water-soluble metabolite was phosphorylcholine. TPA stimulated extracellular choline accumulation to 183% and 351% of basal release after 5 and 20 min respectively and cellular phosphorylcholine production to 136% of basal values after 20 min. These results are consistent with a model in which protein kinase C activation by TPA leads to arachidonic acid mobilization from decidua-cell phospholipid by a mechanism involving phospholipase A-mediated PI hydrolysis and phospholipase C-mediated PC hydrolysis, coupled with further hydrolysis of the 1,2-diacylglycerol product.

This report describes two cases of twin pregnancy in which continuous heart rate monitoring of both twins was successfully carried out during labour. In both cases monitoring permitted early diagnosis of fetal distress and both mothers were delivered by caesarean section. Continuous fetal heart rate monitoring permits diagnosis of fetal distress in the second twin much earlier than conventional methods.