Cardiovascular, metabolic and fetal brain function observation following total cord occlusion.

The effect of total cord occlusion (TCO) on the time sequence of fetal oxygenation, metabolic and cardiovascular parameters and on brain function of the sheep fetus was studied. It was also of importance to differentiate between cardiovascular alteration following TCO due to hypoxia and baroreceptor response, respectively. The investigations were performed on 11 near term pregnant sheep with dated gestational age of 126--137 days. Catheters were placed in the fetal aorta for monitoring fetal arterial blood pressure (FA BP), fetal heart rate (FHR). Blood samples were drawn and analysed for pH, PCO2 and SO2. An electromagnetic flow probe was placed around the common umbilical vein. Fetal EEG was measured over the right hemisphere. All parameters were studied over a varying time of TCO.

The effect of umbilical vein occlusion on fetal oxygenation, cardiovascular parameters, and fetal electroencephalogram.

In 11 fetal sheep experiments, the blood pressure in the fetal aorta (FA) and in the umbilical vein (UV) was measured following umbilical vein occlusion (UVO), as was the fetal heart rate (FHR), pH, Pco2, and oxygen saturation (So2) in both fetal vessels, and umbilical blood flow (Qumb) of the common UV. The fetal electroencephalogram was recorded continuously throughout the experiment. The results (No. = 17) were grouped according to the response of FA So2 into moderate (So2greater than40 per cent, mean 49.8, S.D. 6.3, and severe So2less than40 per cent, mean 20.4, S.D. 9.2). After 8 to 10 seconds, the fetal blood pressure in FA increased. Umbilical vein blood pressure increased to 25 mm. Hg (S.D. 8) and 35 mm. Hg (S.D. 9) in the moderate and severe groups, respectively. As a result of the decreased perfusion pressure (FA-UV blood pressure) across the fetal side of the placenta, the Qumb fell from 147 ml. per kilogram per minute (S.D. 57) and 30 ml. per kilogram per minute (S.D. 55) to 84 ml. per kilogram per minute (S.D. 48) and 120 ml. per kilogram per minute (S.D.22), respectively. The fall in FA So2 was related to the decrease in Qumb: FA So2=37.6 x log Qumb - 22.8 (2alphaless than 0.001). There was a mild decrease in So2 from 70 to 55 per cent when Qumb fell from 250 to 120 ml. per kilogram per minute. Below 80 to 120ml. per kilogram per minute, the fall in FA So2 was almost linear. The So2 in the UV remained constant so that arteriovenous difference for oxygen (AV Do2) increased. Oxygen consumption decreased almost linearly when Qumb fell below 80 to 120 ml. per kilogram per minute. The fetal electroencephalogram showed no significant change in voltage and the faster activities. From these observations, it is concluded that a decrease in Qumb following UVO jeopardizes the fetus only if a critical Qumb of 80 to 120 ml. per kilogram per minute and fetal artery So2 of 50 to 60 per cent is achieved.

The effects of fetal thyroidectomy in the ovine fetus.

Cerebral function and metabolism, morphology and histology of the nervous system, and lung maturity in terms of surfactant production were studied at term in five sheep fetuses thyroidectomized at gestational ages ranging from 104 to 111 days. Compared to age-matched controls, body weight (thyroidectomized animals, 2.8 +/- 0.11 kilograms; controls, 3.9 +/- 0.2 kilograms; P less than 0.0005) and brain weight (thyroidectomized animals, 43.51 +/- 1.38 grams; controls, 48.49 +/- 1.75 grams; P less than 0.05) were significantly reduced. In the nervous system, morphology, histology, brain function, and metabolism were not significantly different from those of the controls. Lung weight was less, but not significantly, and surfactant production was not deficient as compared to that of age-matched controls. The failure to find any disturbance of maturation in the brain and lungs of fetuses thyroidectomized at 104 to 111 days may be related to the relative maturity of the sheep fetus at this age.

The association of umbilical cord complications and variable decelerations with acid-base findings.

Variable decelerations during the last 2 hours of labor were associated with an abnormally positioned umbilical cord at delivery in 52% of cases. In cases where an abnormally positioned umbilical cord was seen at delivery, 89% had been preceded by variable decelerations. Cord compression resulted in an A-V difference in pH that was significantly increased when compared to a control group. This was mainly due to a decrease in the pH of the umbilical artery. The pathophysiology of cord compression is discussed.

Correlation of the oxytocin challenge test with perinatal outcome.

A total of 234 oxytocin challenge tests (OCT) were performed on 100 high-risk patients. The results were negative (N) in 68 of these 100 patients, suspicious (S) in 22, and positive (P) in 10. The incidence of late decelerations during labor was N, 5%; S, 40%; P, 86%; and meconium staining of the amniotic fluid was N, 4%; S, 5%; and P, 30%. The cesarean section rate was N, 16%; S, 36%; and P, 60%; and of these the cesarean section rate for fetal indications was N, 9%; S, 25%; and P, 67%. The overall perinatal mortality in the study group was 2% (N, 1.5%; S, 0%; P, 10%). The results confirm the negative OCT as innocuous and positive OCT as the most ominous. They also indicate that the majority of patients with positive OCT can be delivered vaginally without endangering the fetus if fetal scalp blood pH determinations can be performed.

Correlation of fetal heart rate patterns and fetal pH with neonatal outcome.

Fetal monitoring data in 200 consecutive cases was evaluated in the second hour prior to delivery to determine how neonatal outcome could be most accurately predicted. It was found that the correlation between ominous fetal heart rate-uterine contraction (FHR-UC) patterns and a depressed Apgar score at 1 minute was, at best, 37%. However, where the last fetal scalp blood pH (FSB-pH) was less than or equal to 7.2, neonatal depression occurred in 88% of cases. FSB-pH, therefore, provided a more reliable means of diagnosing fetal distress.

Erythrocyte 2,3-diphosphoglycerate in normal and hypertensive gravid women and their newborn infants.

Red blood cell 2,3-diphosphoglycerate (2,3-DPG) levels were studied in 227 normal gravid women in all stages of pregnancy, active labor, and early post partum. An increase to peak levels was observed at 19 to 22 weeks followed by a gradual fall toward normal. During labor and early post partum, 2,3-DPG again rose significantly above levels observed at term. Serial 2,3-DPG values through the third trimester, labor, and postpartum period in 11 hypertensive mothers and 20 normal gravid control subjects and their newborn infants were studied. Maternal 2,3-DPG levels were significantly higher in the hypertensive mothers when compared to control mothers at similar gestational stages. However, no difference in 2,3-DPG levels was observed when newborn infants of hypertensive mothers were compared with those of normal control subjects.

The effect of methadone on fetal brain function.

The effect of methadone on fetal brain function in terms of the electroencephalogram (EEG) was studied in eight short-term fetal sheep experiments by single injections of 5 to 20 mg. of methadone into the fetal circulation. Plasma methadeone concentrations (determined by radioimmunoassay) greater than 0.065 mg. per cent were associated with an immediate brief decrease in carotid blood flow, a rapid decrease in frequency and amplitude in the EEG that occasionally became isoelectric but recovered, and immediate and relatively prolonged bradycardia. Similar cardiovascular observations were obtained with plasma methadone concentrations less than 0.065 mg. per cent, but the EEG changes were either minimal or not observed. These results indicate that uptake of methadone by the fetal brain is rapid and that electrical activity and heart rate are affected.

Correlation of fetal heart rate-uterine contraction patterns with fetal scalp blood pH.

The significance of fetal heart rate-uterine contraction (FHR-UC) monitoring as a means of predicting the condition of the fetus during labor was studied by correlating 460 fetal pH determinations obtained from 216 patients with the analysis of the 20-minute FHR-UC record preceding the fetal scalp blood sample. Both qualitative and quantitative analyses of the FHR-UC record were performed. The results indicate a less than 10% chance of fetal pH less than or equal to 7.250 with an normal baseline FHR and no periodic changes or with periodic accelerations, early decelerations, and uncomplicated baseline bradycardia or tachycardia. Variable or delayed decelerations with a total surface area (TSA) of 1-100 for the 20-min period were associated with a fetal pH less than or equal to 7.250 in 23 and 34% of cases, respectively. Variable or delayed decelerations with a TSA greater than 100 had a 35 or 47% chance of fetal pH less than or equall to 7.250. It is concluded that FHR-UC monitoring can be used to screen the innocuous from the ominous periodic change but that fetal scalp blood pH must be obtained to identify accurately the true from the false-positive ominous pattern.

Effect of alcohol on fetal cerebral function and metabolism.

The effect of maternal alcohol infusions on fetal cerebral function in terms of the electroencephalogram (EEG) and fetal brain metabolism was studied in 10 fetal sheep experiments. A 9.75 per cent alcohol-dextrose solution was infused at the rate of 15 c.c. per kilogram of maternal weight for 1 or 2 hours. Fetal cerebral uptake of oxygen was unaffected. Blood flow was significantly increased as a result of a greater decrease in resistance than decrease in blood pressure. The cerebral uptake of glucose and the glucose-oxygen utilization ratio were significantly increased. The EEG showed a decrease in amplitude and slowing of the dominant rhythm as the blood alcohol concentration increased and became isoelectric on occasion during the postinfusion period associated with a severe fetal acidosis.

Priming of the uterine cervix with oral prostaglandin E2 in the term multigravida.

A double-blind study evaluating two dose schedules of oral prostaglandin E2 (PGE2) was conducted in 56 normal "unripe" multiparas at term. The effect of PGE2 was evaluated by comparing the change in Bishop score of the cervix and patient's response to oxytocin induction of labor after the prostaglandin priming. In the two study groups (one group on a fixed PGE2 dosage and the other on a variable drug regimen) an average change of more than three points in the Bishop score was observed. In control group no significant change in cervical ripeness was observed. Nine of the 32 patients (28%) receiving prostaglandin delivered during the priming phase of the study, whereas only 1 control patient (4.2%) delivered during priming. Six of 24 control patients (25%) failed to deliver, wheras only 3 of 32 study patients (9%) failed. In the successfully induced patients, the response to oxytocin, as expressed by the time to active phase, total time of labor, and mean dose of oxytocin required, did not vary significantly when control and study groups were compared. It is concluded that PGE2 at either dosage schedule is effective in changing the Bishop score of the cervix and that it is not feasible to titrate the PGE2 dose in order to effectively ripen the cervix without a very high incidence of induction of labor. In those cases where priming was completed, without accidental delivery, the induction phase was successful more than 90% of the time. No adverse effect to mother or baby was observed during this study.

Prolonged fetal bradycardia with recovery--its significance and outcome.

bradycardia lasting more than 21/2 minutes with a decrease in FHR of more than 30 b.p.m. were observed in the course of 15 monitored labors. The mean fetal pH during the 20 minutes following the bradycardia (early recovery) was significantly less than the mean pH obtained 30 minutes or more after the bradycardia (late recovery). Various types of periodic heart rate changes were observed during the early recovery period but few persisted into late recovery. Vaginal delivery occurred in 13 of 15 patients. Two cesarean sections were performed for indications unrelated to the prolonged bradycardia. The 5 minute Apgar score of all 15 neonates was 7 or greater.

Placental transport of alcohol and its effect on maternal and fetal acid-base balance.

The placental transport of alcohol and its effect on maternal and fetal acid-base balance studied in 10 sheep experiments by the maternal infusion of a 9.75 per cent solution of alcohol-dextrose at a rate of 15 c.c. per kilogram for 1 or 2 hours. Serial maternal and fetal blood sampling during and following the alcohol infusion revealed rapid placental diffusion of alcohol, a highly significant correlation between maternal and fetal blood alcohol concentrations, and a similar peak concentration of approximately 0.230 Gm. per 100 ml. in maternal and fetal blood that differed only in time of onset during the 1 and 2 hour infusion periods. Blood alcohol concentrations remained high for several hours during the postinfusion period. A significant maternal hyperlactacidemia and hyperglycemia were noted but did not result in significant alterations in maternal acid-base balance. An initial fetal metabolic acidosis and later mixed acidosis were observed during the alcohol infusion and worsened during the postinfusion period.