The effects of veno-venous extracorporeal membrane oxygenation on hypoxic fetal lambs.

OBJECTIVE: The purpose of this study was to determine the applicability of veno-venous extracorporeal membrane oxygenation (V-V ECMO) to support fetal oxygenation in utero. METHODS: An ECMO system with a centrifugal pump was applied to ten chronically instrumented fetal lambs, at 126 or 127 days of gestation. Blood was obtained through a double-lumen catheter inserted into the right atrium. After oxygenation, the blood was returned through a single-lumen catheter into either the carotid artery (veno-arterial; V-A ECMO) or the right atrium (V-V ECMO). After fetal hypoxia had been experimentally produced, V-A ECMO or V-V ECMO was instituted to maintain fetal oxygenation. We compared fetal blood gases with both routes of ECMO. RESULTS: Oxygen partial pressure (pO(2)) in the fetal cranial carotid artery decreased to 12.9 +/- 0.6 mmHg after reducing the fraction inspiratory oxygen of the mother. After instituting V-A ECMO, pO(2) was found to be 23.5 +/- 2.6 mmHg; after instituting V-V ECMO, pO(2) was found to be 20.3 +/- 1.9 mmHg. Thus, fetal acidosis increased under both procedures. Fetal heart rate and blood pressure were not altered significantly during the experiments. CONCLUSIONS: This study indicates that V-V ECMO could more effectively and less traumatically maintain oxygenation in hypoxic fetal lambs.     

The influence of maternal oxygen inhalation for 30 to 60 minutes on fetal oxygenation

Healthy parturients with uterine displacement received oxygen inhalation before and during spinal anesthesia for elective cesarean section. Oxygen was administered through a mask (group OH2 : 20 cases) or via a nasal cannula (group OH1: 20 cases) for 33 to 69 minutes. All patients were in the right lateral position prior to spinal block and were in the left tilt after the anesthesia. The fetal blood-gas values were relatively evaluated among the OH2, OH1 and OH groups which received oxygen via a cannula for 9 to 17 minutes. The maternal artery PO2 values for the OH2 group (the mean: 491.7 +/- 61.4mmHg) were significantly higher than those for the OH1 and OH groups (244.5 +/- 28.0 and 225.0 +/- 62.9mmHg, respectively). The umbilical vein PO2 (46.1 +/- 7.5mmHg) and SO2 (87.6 +/- 6.3%) of the OH2 group were also significantly greater than those of the other groups (PO2: 36.1 +/- 4.1mmHg, SO2: 77.3 +/- 6.0% in the OH1 group and PO2: 37.5 +/- 6.4mmHg, SO2: 77.6 +/- 10. 3% in the OH group, respectively). The Apgar scores and both the maternal and fetal acid-base values for all groups were excellent. The umbilical vein to artery PO2 and SO2 gradients of the OH2 group were significantly greater than those of the other groups. It is emphasized that maternal hyperoxia with uterine displacement improves fetal oxygenation without adversely affecting the fetal acid-base state, even if it is excessive and maintained for 60 minutes.     

The effects of isoproterenol on fetal oxygenation.

Infusion of isoproterenol (1 microgram/kg/min, i.v.) into the anesthetized pregnant rhesus monkey near term consistently reduced fetal oxygenation, despite diminishing myometrial activity. The decline in pO2 of fetal arterial blood (mean = 4.3 +/- 2.3 mmHg S.D.) was accompanied by an increase in pCO2 tension (mean = 4.6 +/- 2.7 mmHg) and a decline in pH (mean = 0.04 +/- 0.02 S.D.). There was an increase in heart rate and a widening of pulse pressure in the mother and also in the adequately oxygenated fetus providing evidence that the agent crosses the placenta. The poorly oxygenated fetuses developed bradycardia and hypotension. Administration of isoproterenol directly to the fetus elicited similar changes in the composition of blood, and in blood pressure and heart rate, to those observed after administration of the agent to the mother.     

Effect of maternal oxygenation on fetal blood gas status in shiba goat fetuses

The purpose of this study is to investigate the effect of maternal oxygen administration on the fetal blood gas status. Five Shiba goat fetuses were used whose gestational days were 134 +/- 4 days. Maternal and fetal pH, pO2, pCO2, B.E., and hematocrit were measured every 30 minutes during 4 l/min oxygen administration for 60 minutes. Maternal arterial blood pO2 increased from 95.5 +/- 19.6 mmHg to 262.6 +/- 75.8 mmHg at 30 minutes and to 207.8 +/- 110.1 mmHg at 60 minutes. Fetal arterial blood pO2 increased significantly from 18.4 +/- 3.0 mmHg to 24.4 +/- 5.8 mmHg and 23.6 +/- 6.9 mmHg, respectively. There was a significant positive correlation between maternal pO2 and fetal pO2. The increase in fetal pO2 was small when the control pO2 was less than 17 mmHg. Although maternal pH did not change significantly, fetal pH decreased significantly from 7.29 +/- 0.07 to 7.25 +/- 0.07 at 60 minutes. Also fetal hematocrit decreased significantly from 33.9 +/- 5.2% to 32.8 +/- 5.4% at 60 minutes. Neither maternal nor fetal pCO2 and B.E. changed significantly. Therefore, we concluded that the effect of maternal oxygen administration on fetal pO2 was small when the fetus was already hypoxic. Also 60 minutes' oxygen administration may cause the decrease in fetal pH and hemodilution.     

Fetal blood saturation during the 1st and 2nd stage of labor and its relation to the neonatal outcome

OBJECTIVE: The aim of this study was to evaluate fetal blood oxygenation (SpO(2)) by means of continuous pulse oximetry during labor and its relation to the neonatal outcome. MATERIALS AND METHODS: Fetal SpO(2) was measured continuously during labor with a noninvasive pulse oximetry for fetal application. The average, minimum and maximum SpO(2) levels were evaluated separately for the 1st and 2nd stage of labor. The average SpO(2) of the fetus was compared to the neonatal outcome assessed by the levels of pH, pO(2) and pCO(2) in the fetus' umbilical blood and to the Apgar score. RESULTS: Twenty-eight patients were monitored by fetal pulse oximetry. All the patients had normal, vaginal delivery. During the 1st stage of labor, the average fetal SpO(2) was 51.78 +/- 8.00%, the minimum SpO(2) level was 37.61 +/- 9.86%, and the maximum level of SpO(2) was 63.82 +/- 7.37%; in the 2nd stage of labor, the average SpO(2) level was 44.91 +/- 8.28%, the minimum level was 35.00 +/- 9.22%, and the maximum SpO(2) was 52.30 +/- 9.36%. A significant decrease in the fetal average and maximum SpO(2) levels was observed between the 1st and the 2nd stages of labor (the average SpO(2) was 51.78 +/- 8.00% vs. 44.91 +/- 8.28%, p = 0.00029; the maximum SpO(2) was 63.82 +/- 7.37% vs. 52.30 +/- 9.36%, p < 0.00001). A significant correlation between the average SpO(2) level during the 1st and 2nd stage of labor and the Apgar score at the first minute of outcome was observed (R = 0.43, p = 0.031). No relationship between the fetal SpO(2) during the 1st and the 2nd stage of labor and the pH, pCO(2), and pO(2) in the fetal umbilical blood were observed. CONCLUSIONS: During the 2nd stage of labor, a significant decrease in the fetus' SpO(2) can be observed. The fetus' SpO(2) level >30% in the 1st and 2nd stage of labor was related to the good neonatal outcome. The assessment of the fetal SpO(2) during the 1st stage of labor seems to be important in predicting neonatal outcome.     

Continuous Fetal Scalp and Carotid Artery Oxygen Tension Monitoring in the Sheep.

Fetal scalp and carotid PO2 were recorded continuously by polargraphic oxygen electrodes at several levels of maternal oxygenation. The results were compared to measurements obtained by intermittent blood samples using the radiometer blood gas analyzer. There was a good correlation between the PO2 values measured by the implanted oxygen electrodes and by conventional analyses of blood samples collected anaerobically. Electrode measurements differed from the control radiometer values by a mean of +/- 1.2 mmHg; 2 SD= +/- 2.50. Scalp PO2 recordings were lower but paralleled the carotid recordings under varying degrees of maternally inspired O2 concentrations. Thus scalp PO2 levels reflect closely those in the central fetal circulation. Administration of 95% O2 to the mother resulted in a 27% increase of scalp PO2 and a 29% increase in the carotid artery PO2 when compare to room air.     

Gas exchange in extracorporeal circuits for neonates: comparison of three different canulation systems during animal experiments

During twenty animal experiments the effectiveness of the gas exchange during extracorporeal membrane oxygenation (ECMO) was evaluated. Arteriovenous, venovenous and venoarterial perfusion systems were compared. While PO2 saturation values were sufficient in all three groups the PO2 values were significant higher during arteriovenous perfusion (84.22 +/- 3.5 mmHg) compared to venovenous 71.99 +/- 7.3 mmHg) and venoarterial (65.11 +/- 4.5 mmHg) perfusion (p less than 0.001). PCO2 values correlated with the flow in the extracorporeal circuit in all three groups. The absolute values of PCO2 were significantly lowest during venoarterial perfusion (39.68 +/- 3.1 mmHg) compared to the venovenous (42.69 +/- 3.3 mmHg) and the arteriovenous mode (49.96 +/- 4.1 mmHg). These results indicate that perfusion circuits other than the original venoarterial ECMO could provide sufficient gas transfer for respiratory insufficient neonates while avoiding points of criticism of such systems.     

Effects of ethanol on the circulation and acid-base balance of pregnant sheep

Nine infusions of 15 cc/kg/120 min of 9.5% ethanol were administered to 4 chronically catheterized ewes, at 109-135 days' gestation. Stabilization periods ranged from 6 to 28 days postoperatively. Maternal and fetal concentrations of ethanol were almost identical (r = 0.9925), with peak levels of 122 +/- 20 mg/100 ml (mean +/- 1 SE) and 121 +/- 19 mg/100 ml, respectively, at the end of infusion. Maternal pH decreased from 7.50 +/- 0.02 to 7.44 +/- 0.02 (P less than 0.005) at 120 minutes. Maternal glycemia increased from 76 +/- 14 mg/100 ml to 162 +/- 23 mg/100 ml (P less than 0.005) at 120 minutes. Maternal heart rate, blood pressure, PO2, O2 content, PCO2, and bicarbonate remained unchanged. Fetal PO2 increased during and following infusion from 18.9 +/- 0.9 mmHg to 22.0 +/- 1.0 mmHg (P less than 0.005) at 180 minutes. Fetal blood pressure increased from 51.3 +/- 3.1 mmHg to 53.7 +/- 3.3 mmHg (P less than 0.01) at 30 minutes. Fetal pH, PCO2, glucose, and lactate levels remained unchanged. The authors conclude that ethanol crosses the sheep placenta readily, causes maternal acidosis and hyperglycemia, and increases fetal PO2, blood pressure, and heart rate without any effects on fetal acid-base status.     

Unloading of baroreceptors by carotid occlusion does not increase heart rate in fetal sheep

Unloading of baroreceptors by carotid occlusion does not increase heart rate in fetal sheep; Objectives: To test the hypothesis that in fetal sheep reduction of carotid sinus pressure by carotid occlusion increases heart rate. Study design: Fetal sheep (gestational age 121-132 days) were chronically instrumented with bilateral carotid occluders, catheters and electrodes (ECG) to measure systemic arterial and carotid sinus (CSP) blood pressures, and fetal heart rate. Results: Bilateral carotid occlusion (BCO) increased mean arterial blood pressure from 46+/-7 mmHg to 53+/-8 mmHg (mean+/-S.D.) while CSP decreased from 44+/-7 mmHg to 17+/-7 mmHg. Fetal heart rate fell during occlusion significantly from 186+/-34 bpm to 159+/-26 bpm (n=20 animals). Infusion of phenylephrine (8.5-20 microg min(-1)kg(-1)) or methoxamine (60-200 microg min(-1)kg(-1)) increased mean blood pressure from 44+/-6 to 61+/-9 mmHg, and fetal heart rate decreased from 186+/-30 to 132+/-31 bpm (n=12). BCO increased systemic arterial pressure further to 70+/-11 mmHg whereas carotid sinus pressure was reduced to 31+/-13 mmHg. However, average heart rate did not increase significantly (136+/-28 bpm). Conclusion: We conclude that in contrast to adult animals, in fetal sheep carotid occlusion with subsequent unloading of baroreceptors does not increase heart rate even when the baroreflex had been activated by arterial hypertension. It seems likely that stimulation of carotid chemoreceptors prevents the expected baroreceptor mediated heart-rate response.     

Improved oxygenation with prone positioning in neonates: stability of increased transcutaneous PO2.

To evaluate the effect of body position on oxygenation and ventilation in neonates over a prolonged period, infants with respiratory disease were followed by transcutaneous (tc) monitoring for alterations in tcPO2 and tcPCO2 with position changes. In 14 studies of seven patients, prone positioning was compared with supine positioning over a 6-hour interval. All patients were premature, were receiving supplemental oxygen, and had respiratory disease secondary to prematurity. The median gestational age was 29 weeks; all infants were 2 months old or less at the time of the study. Prone positioning resulted in a significantly higher tcPO2; mean (+/- SD) tcPO2 increased from 63 (+/- 11.6) mm Hg to 71 (+/- 14.6) mm Hg, and decreased to 65 (+/- 11.2) mm Hg when the infant was returned to supine (P less than .05). This increase in tcPO2 was stable throughout 2 hours in the prone position. No significant change in tcPCO2 was detected. Infants were also found to spend a greater proportion of time sleeping when prone (75% +/- 13% vs 33% +/- 14%; P less than .05). These finding suggest that improvement in oxygenation with the prone position is stable over an extended period in the sick preterm infant.     

Maternal caffeine administration and cerebral oxygenation in near-term fetal sheep

The authors test the null hypothesis that maternal caffeine administration will not significantly alter fetal cerebral oxygenation. The authors measured fetal arterial blood gases, cortical tissue O(2) tension (tPO(2)), sagittal sinus blood gases, and laser Doppler cerebral blood flow in response to a 30-minute caffeine infusion (400 mg intravenously) into 7 near-term pregnant ewes, and they calculated fractional O(2) extraction and relative cerebral metabolic rate for O(2) (CMRO(2)). Following maternal caffeine infusion, both fetal cortical tPO(2) and sagittal sinus (HbO(2)) decreased significantly, from 10.7 +/- 0.9 to 6.8 +/- 1.1 Torr and from 46% +/- 2% to 37% +/- 6%, respectively. This was associated with significant 20% to 30% increases in fractional O(2) extraction and CMRO( 2). Fetal arterial blood gas values did not change significantly. In conclusion, maternal caffeine administration significantly decreases cerebral oxygenation without affecting systemic oxygenation in fetal sheep. The authors speculate that for a fetus that may be otherwise compromised, this increase in CMRO(2) with decreased cortical tPO(2) could present a problem.     

Plasma endothelin-1 and atrial natriuretic peptide levels during prolonged (24-h) non-acidemic hypoxemia in fetal goats.

OBJECTIVE: The purpose of this study was to investigate the effects of prolonged (24-h) non-acidemic hypoxemia on plasma endothelin-1 and atrial natriuretic peptide (ANP) in fetal goats. METHODS: During continuous infusion of nitrogen into the maternal trachea, fetal plasma endothelin-1 and ANP levels were measured in nine chronically instrumented goat fetuses at 117-129 days' gestation. Endothelin-1 and ANP were measured by radioimmunoassay. RESULTS: Fetal arterial pO(2) decreased significantly from 23.1 +/- 1.0 mmHg (control) to 15.2 +/- 0.9 mmHg during the first 2 h of hypoxemia and to 15.7 +/- 1.1 mmHg at the end of the experimental period of hypoxemia. The plasma endothelin-1 concentration increased from 10.6 +/- 1.9 pg/ml to 20.4 +/- 4.3 pg/ml (p < 0.05) during the first 2 h and was 19.7 +/- 2.4 pg/ml (p < 0.01) at the end of the experimental period. The plasma ANP concentration also increased, from 20.3 +/- 5.5 pg/ml to 23.0 +/- 4.7 pg/ml in the first 2 h and then to 58.0 +/- 8.8 pg/ml (p < 0.05) at the end of the experimental period. There was a significant negative correlation between fetal plasma endothelin-1 and pO(2), but no significant correlation was found between fetal plasma ANP and pO(2). CONCLUSIONS: Prolonged non-acidemic hypoxemia induces a continuous increase in fetal plasma endothelin-1 and ANP levels. Fetal plasma ANP increases time-dependently but endothelin-1 remains constant during hypoxemia.     

Perinatal outcome in women with severe chronic hypertension during the second half of pregnancy.

OBJECTIVES: To determine the perinatal outcome associated with severe chronic hypertension (SCH) in pregnancies of > or =20 weeks' gestation. METHODS: A retrospective analysis of data obtained prospectively of patients with SCH (> or =160/110 mmHg) who were hospitalized and delivered during a 5-year period. Each patient received intensive monitoring of the clinical status throughout the hospitalization (mother, fetus and neonates). Antihypertensive drugs were used for blood pressure > or =160/110 mmHg, glucocorticoids for pregnancies of 24-34 weeks and magnesium sulfate for women with superimposed pre-eclampsia (SPE). The main outcome measures were fetal and neonatal deaths, fetal growth restriction (FGR), major neonatal complications and length of stay in the neonatal intensive care unit (NICU). RESULTS: Of 154 women studied, 78% developed SPE and the mean week's gestation at delivery was 34.5+/-4.6. The average birth weight was 2329+/-1011 g. and the FGR was 18.5%. Four patients had a dead fetus at the time of admission, eight during the hospitalization and there were six neonatal deaths resulting in perinatal mortality of 11.4%. Thirty-eight babies were admitted to the NICU, average stay was 14.8 days. The most common contributors to neonatal mortality and morbidity were pulmonary complications and sepsis. CONCLUSIONS: This study found that the neonatal outcomes in pregnancy with SCH are better than the historical experience, but preterm deliveries, cesarean section, SPE, abruptions and total perinatal mortality remains very high.     

The usefulness of the intrapartum fetal pulse oximetry in anticipating the neonatal outcome

OBJECTIVE: The aim of the study was to evaluate the usefulness of the intrapartum fetal pulse oximetry in anticipating the neonatal outcome. MATERIALS AND METHODS: The saturation of the fetal blood (SpO2) was measured during labor with non-invasive pulse oximeter designed for fetal application. The average, minimum and maximum SpO2 were evaluated separately for the first and the second stage of labor. The average SpO2 of the fetus was compared to neonatal condition assessed by umbilical vein pH, pO2 and pCO2 and according to Apgar score. RESULTS: Twenty patients have been monitored with fetal pulse oximetry. All those patients had normal vaginal delivery. During the first stage of labor, the average fetal SpO2 was 51.94 +/- 8.03%, the minimum SpO2 was 38.35 +/- 9.15%, and the maximum SpO2 was 63.35 +/- 7.75%; in the second stage of labor average fetal SpO2 was 43.82 +/- 7.16%, minimum SpO2 was 34.35 +/- 7.79% and the maximum SpO2 was 50.94 +/- 8.37%. A significant decrease in fetal average and maximum SpO2 occurred from stage I to stage II of labor (average SpO2: 51.94 +/- 8.03% vs. 43.82 +/- 7.16%, p = 0.0002; maximum SpO2: 63.35 +/- 7.75% vs. 50.94 +/- 8.37%, p < 0.00001). The significant correlation between the average SpO2 during the first stage of labor and umbilical vein pH (R = 0.60, p = 0.02) and pO2 (R = 0.54, p = 0.04) was found. No relationship between fetal SpO2 in the first and second stage of labor and Apgar score was observed. CONCLUSIONS: 1. The second stage of labor results in significant decrease in fetal SpO2. 2. The fetal SpO2 > 30% in the first and second stage of labor is related to good neonatal outcome. 3. The fetal SpO2 assessment in first stage of labor seems to be important in newborn's acidosis and hypoxemia predicting.     

Comparative study of application techniques for the tcPCO2 measurement in the fetus

In order to investigate the advantages and shortcomings of two application techniques proposed for the tcPCO2 electrode in the fetus we performed a trial using two electrodes with different modes of fixation synchronously. Comparing the transcutaneously measured values with the values of the fetal blood we found a statistically significant correlation for both techniques (r = 0.83 and 0.80, respectively). The mean values of the tcPCO2 though were significantly higher when the suction fixation was used compared with the glue fixation.     

Effect of continuous lumbar epidural anaesthesia during labour on fetal transcutaneous carbon dioxide.

The effect of epidural anaesthesia during labour on fetal transcutaneous carbon dioxide (tcPCO2) was observed on 27 fetuses. Our results show that in the course of epidural anaesthesia there is an increase in fetal tcPCO2. We can see a slight increase even before administering the test dose, while preparatory measures are undertaken for the epidural anaesthesia. After administering the test dose and after giving the main dose there is a further increase in fetal tcPCO2, which continues for up to 30 min after the main dose has been given. The results suggest that it is important to consider any pathological conditions in the fetus, so as to avoid the possibility of additionally endangering the fetus during epidural anaesthesia.     

Effect of arginine vasopressin on arterial oxygen partial pressure in the chronically catheterized fetal lamb

Fetal plasma 2,3-Diphosphoglycerate (2,3-DPG) and glucose levels were observed during infusion of arginine vasopressin into 6 chronically catheterized fetal lambs. Low dose infusion of arginine vasopressin (5-10 mIU/min.) did not change fetal arterial blood gases significantly. At a high concentration of vasopressin (20-40 mIU/min.), infusion for 60 minutes increased fetal arterial pO2 by approximately 5 mmHg (p less than 0.005 by paired t-test), and decreased pCO2 by approximately 2 mmHg (p less than 0.005 by paired t-test) without significant changes in pH. Neither low nor high dose infusion of arginine vasopressin was accompanied by significant changes in 2,3-DPG or the glucose level.     

Effects of acute hypoxemia on fetal movement in the fetal lamb

Chronically instrumented pregnant models were established using 5 Dorset-Rambouillet pregnant ewes with gestational age between 120 and 138 days. Observation of fetal movements were started on the 3rd postoperative day or later when recovery from the surgery to the physiological condition was confirmed by maternal and fetal biophysical parameters. Fetal movements were observed using real-time ultrasound equipment with linear-array transducer placed on the maternal abdomen. Observation encompassed the control period which lasted one hour followed by an experimental period of fetal hypoxemia created by decreasing maternal FIO2. Observation was also continued during the recovery period when the mother was re-exposed to room air. Maternal and fetal samples were periodically obtained during these periods. Frequency of fetal movements was studied in 10 minute periods under the control and hypoxemic conditions. All fetuses exhibited movements during the control period, ranging 1-42 movements/10 minutes, the mean incidence being 16.9 movements/10 minutes. During fetal hypoxemia (average PaO2 decrease: 8.6 mmHg), fetal movements were significantly reduced to 5.5 movements/10 minutes with complete cessation in some cases. In 4 animals which exhibited complete cessation of both fetal movement (FM) and fetal breathing movement (FBM), FBM disappeared before FM, and reappearance of FM was following by FBM during recovery from hypoxemia.     

Fetal breathing and adaptation to maternal hemorrhage in the sheep.

The effect of maternal hemorrhage in chronic preparations was studied on fetal lambs in the last month of gestation. Fourteen to 20 per cent of maternal blood was estimated to have been removed within 30 minutes, which resulted in a drop of 30 per cent of mean maternal arterial pressure. A fetal bradycardia started 28 +/- 13 minutes after the beginning of maternal hemorrhage. It lasted 30 +/- 15 minutes and was concomitant with a rise in fetal arterial pressure. It was followed by a long-lasting fetal tachycardia of 130 +/- 38 minutes and was corrected only by reinfusion of blood to the mother. The fetal blood gases demonstrated a mild asphyxia with a persistent metabolic acidemia until reinfusion of blood to the mother. Maternal and fetal plasma cortisol levels rose significantly at the end of the hemorrhage. Tracheal fluid flow did not change. Fetal breathing recorded 20 hours before and 24 hours after the experiment did not show consistent changes, but during fetal bradycardia there was no fetal breathing. Recent clinical investigations in this field have been made in the human fetus to estimate standards of fetal well being. These peculiar animal experiments do not show any significant improvement by recording fetal breathing over the recording of prelabor fetal heart rate.     

Glue fixation of the tcPco2 electrode for fetal monitoring

tcPco2 monitoring on the fetal scalp potentially is a beneficial and additional new tool for the surveillance of the unborn child. During a clinical trial we investigated the tcPco2 monitoring using the glue fixation technique. A modified Severingshaus electrode was applied on a prepared area on the fetal scalp by means of an endoscope. The attempt of application was successful in 224 out of 245 cases, while reapplication was only necessary in 8 cases. The accuracy of the tcPco2 measurement using glue fixation was sufficient at both measuring temperatures (39 degrees C and 44 degrees C). The correlation coefficient comparing the data with the tcPco2 of the fetal blood was 0.74 respectively 0.81. The development of a caput succedaneum leads to higher absolute values of the tcPco2. When a caput succedaneum has developed in the measuring area the mean value of the tcPco2 is significantly higher (62.70 mmHg instead of 55.14 mmHg respectively 68.98 mmHg instead of 65.98 mmHg) at 39 degrees C respectively 44 degrees C. No significant influence of different preparation techniques of the measuring site has been found during this investigation. The glue fixation technique leads to a reliable recording of tcPco2 in the fetus during labor, when the electrode is placed in a central and not compressed position on the lower pole of the fetus. The disadvantage is the necessity of extensive training of the personnel and the large number of instruments, factors that will interfere with a more widespread use in clinical routine.