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Objectives: Testing of fetal habituation to repeated vibroacoustic stimulation might give additional information concerning the fetal condition and central nervous system (CNS) functioning in postterm pregnancies. This study is designed to investigate whether healthy postterm fetuses are able to habituate and if so, if the habituation pattern of postterm fetuses differs from that of term fetuses., Study Design: Twenty women with an uncomplicated pregnancy beyond 41 weeks gestational age (GA) participated, and 37 women with a GA between 37 and 40 weeks served as controls. The vibroacoustic stimulus was repeatedly applied to the maternal abdomen above the fetal legs for a period of 1s every 30s. A fetal trunk movement within 1s of stimulus application was considered a positive response. Lack of response to four consecutive stimuli indicated habituation. The habituation rate is defined as the number of stimuli applied before the fetus stopped responding. Data were compared using Mann-Whitney U test., Results: Of the 18 postterm fetuses in which the presence or absence of habituation could be established, 14 habituated and four persisted in responding. Twenty-six of the 32 term fetuses, in which the presence or absence of habituation could be established, habituated and six persisted in responding. The habituation rate varied widely in postterm (median of eight stimuli, quartile ranges of 6 and 18) as well as in term fetuses (median of 9.5 stimuli, quartile ranges of 6 and 15). There was no difference in median habituation rate between postterm and term fetuses., Conclusion: The ongoing maturation of the CNS in the last weeks of pregnancy appears not to be reflected in the fetal habituation pattern. Furthermore, the interfetal variability in habituation of healthy postterm fetuses is such that testing of habituation appears not to be suitable for the identification of the fetus at risk for an adverse neonatal outcome.

Observation of the fetal movement and fetal heart rate responses to repeated vibroacoustic stimulation might be useful as a measure to assess fetal well-being. Studies of abnormal fetuses are needed to gain insight in the spectrum of possible responses to stimulation. We present a case of a fetus with trisomy 18 that failed to respond to repeated stimulation.

Pulse oximetry is a technique for estimating arterial oxygen saturation continuously and non-invasively. Reflectance pulse oximetry might become useful for monitoring the fetus during labour but it is much more susceptible to all kinds of physiological variations than the well-established transmission pulse oximetry for neonatal or adult monitoring. This review focuses on the accuracy of reflectance pulse oximetry. Results of human, animal, in vitro and theoretical models indicate that factors such as; blood volume fraction differences, haematocrit, and blood flow differences are major sources for inaccurate pulse oximetry readings in the fetal arterial oxygen saturation range of 10-80%. These factors cannot be overcome by systems using two wavelengths sensors with the 660/890 or 940 nm combination. Reported precision values (S.D. of difference between pulse oximeter and blood sample saturation) range between 2.5 and 12.9% for various 660 nm sensors. Most sensors were tested only once with a limited number of animals. A new 735/890 nm sensor (Nellcor Puritan Bennett) demonstrates a promising accuracy (precision around 5%) in two studies. Various other sensors have also been developed, but are not or scarcely evaluated. Without thorough establishment of the reliability of this technique, clinical fetal oxygen saturation data are still of limited value.

Objective: To determine if oxygen saturation measurement with pulse oximetry (SpO2) in combination with cardiotocograghy (CTG), improves the assessment of the intrapartum fetal condition., Study Design: Four expert obstetricians individually evaluated 119 cases that were monitored during labor: during the first session the CTG data were available, and in the second session CTG and SpO2 data were evaluated. They were instructed to indicate the need for intervention and to estimate the umbilical artery pH., Results: In the non-acidotic group (umbilical artery pH > or = 7.15, n = 112) the average(+/-S.D.) number of interventions decreased from 27(+/-17) to 16(+/-9) when SpO2 was available. This reduction in number of interventions resulted in an significantly increased specificity for two referees. In the acidotic group (n = 7) the average number of interventions also decreased, from 6(+/-2) to 4(+/-2), and as a consequence the sensitivity decreased. The pH estimate based on CTG + SpO2 was higher in both acidotic and non-acidotic fetuses than the estimated pH based on CTG alone., Conclusion: In this study all referees intervened less frequently when SpO2 was used as an adjunct to CTG. This resulted in fewer unnecessary operative interventions, but may also lead to unidentified fetal acidosis. The number of acidotic newborns (n = 7) was too small, however, to draw definite conclusions. Larger studies should address the efficacy of SpO2 in detecting fetal compromise before clinical use can be advocated.

In the fetus, the arterial oxygen saturation (SaO2) in the ascending aorta is higher than in the descending aorta. We questioned whether this difference over the ductus arteriosus (delta SaO2) would change during hypoxaemia. Therefore, six chronically instrumented fetal lambs (119-126 days of gestation) were studied, by changing the inspired oxygen (FIO2) via a tracheal tube to the ewe. The SaO2 was measured intermittently every 15 min with blood samples obtained from the ascending and descending aorta, and continuously with 2 pulse oximeters at both sides of the ductus arteriosus. delta SaO2 was at a level of 3.4-5.3% and had a tendency to decrease at preductal SaO2 levels of 10-20% and at pH levels below 7.25. The precision of the pulse oximeters, expressed as standard deviation of the differences between sample SaO2 and pulse oximeter SaO2, was around 5.0% for the individual calibration curves. This precision was not enough to show details of the course of delta SaO2 between the blood samples. Our results show that there is no change in delta SaO2 across the ductus arteriosus.

Intra-uterine pressure (IUP), intracranial pressure (ICP) and fetal heart rate (FHR) were simultaneously recorded during labor in a severely hydrocephalic fetus. After cephalocentesis, 600 ml of liquor cerebrospinalis was drained. ICP exceeded IUP, but the increase in ICP was less than the increase in IUP during most of the contractions. The FHR showed marked decelerations during uterine contractions and changed gradually into a persistent bradycardia. The pathophysiology of fetal heart rate patterns during labor is discussed and the literature has been reviewed.

This article reviews the major milestones in obstetric research in the past 90 years, which have lead to the wide-spread use of salt restriction during pregnancy. Possibly the most ardent advocate of the view that salt plays a crucial role in eclampsia was De Snoo (1877-1949), a Dutch obstetrician. However, despite many enthusiastic clinical reports, no convincing evidence has ever been produced that salt restriction helps in the prevention of hypertension during pregnancy.

Maternal diazepam medication during labor reduces beat-to-beat variability of the fetal heart rate. In this study, the prolongation of the effect was examined in the newborn. The mother received diazepam: (A) during labor as a tranquilizer, (B) daily in low doses at the end of pregnancy, or (C) in high doses i.v. for (pre-)eclampsia. A control group had no analgesic or sedative during pregnancy or labor. The electrocardiogram (ECG) was recorded daily from each newborn during the first 6 days after birth. After preprocessing of the ECG, the median R-R interval, the long-term irregularity index (LTI index) and the interval difference index (ID index) were calculated. A cubic spline interpolation method was applied to compare the various groups with respect to these heart rate parameters. The median R-R interval showed no particular differences in trend for all groups. The LTI index was decreased in the first days after birth in the chronic diazepam (B), and in the diazepam infusion groups (C), but statistical significance was not reached. The ID index was significantly decreased in the first 1-2 days in the newborns of the acute and chronic diazepam group. In the diazepam infusion group, an even longer lasting effect was observed. Maternal diazepam medication affects the beat-to-beat variability in the newborn. The duration of the effect is dependent on dosage and route of administration.

Plasma concentrations of atrial natriuretic peptide (ANP) were determined ante- and post-partum in 7 healthy primiparous women. ANP was measured at weekly intervals from the 35th week of pregnancy onwards and throughout the puerperium up to the sixth week post-partum. In all seven patients the mean of the ANP values during the first four days post-partum was higher than in late pregnancy. The mean ANP level from the 6th day up to the 42nd day showed a marked decrease compared with the first four days after birth, which, however, did not differ significantly from the mean plasma concentration in late pregnancy. In conclusion, ANP is markedly elevated during the first few days post-partum compared with plasma levels in the normal late pregnancy and the subsequent puerperium.

Intraamniotic pressure was studied in the 30th week of amenorrhea in relationship with fetal intracranial pressure with open-tip catheters. The fetus had a severe hydrocephalus (echoscopy 16 cm) due to a teratologic malformation of the cerebrum. Clinically nonoperative treatment was indicated. Intracranial pressure (X) was invariably higher than intraamniotic pressure (Y) between contractions: Y = 2.04 + 0.54 X, and during contractions: Y = 5.30 + 0.55 X. There was no definite relationship between intrauterine and intracranial pressure, and the fetal tachogram. A definite relationship was established with the supine position of the patient and decelerations in the fetal tachogram. It is suggested that when fetal cardiac decelerations are seen during the first stage of labor it seems advisable to look for factors such as umbilical cord compression and decrease of materno-placental perfusion rather than fetal head compression.

The preejection period (PEP) of the fetal cardiac cycle was studied in the chronically instrumented fetal lamb. An inflatable cuff occluder was positioned around the maternal common internal iliac artery, the pregnant ewe's main uterine blood-supplying vessel. Occlusion of the maternal common internal iliac artery produced a fall in pO2 and pH and a rise in pCO2. Fetal arterial blood pressure increased and PEP shortened, especially in the longer lasting occlusions. Fetal heart rate exhibited a bradycardia also during this type of occlusion. The fetal lamb's cardiovascular adjustments to biochemical changes caused by occlusion of the maternal uterine blood supply appear to be determined during the initial phase of occlusion by a chemoreceptor reflex-induced peripheral vasoconstriction mediated by the adrenergic nervous system. The condition is comparable to the one observed during the second part of the umbilical cord occlusions. The interaction between a supersensitive fetal myocardium and the adrenal release of catecholamines may play a dominant role during the second part of occlusion in the longer lasting experiments. Increase in peripheral resistance in the course of redistribution of blood flow during hypoxemia induces a prolongation of the PEP in the early phase of occlusion; overriding of this effect by an increase in myocardial contractility due to rising levels of adrenal catecholamines abbreviates the PEP in the later part of the longer lasting occlusions.

The distribution of gas values of umbilical cord blood was studied in an university clinic population during a period of 3 yr. All patients in labor were guided by obstetrical personnel and continuous electronic fetal monitoring (CTG). Microblood analyses were performed on indication of the CTG. The tenth percentile for the total population for umbilical artery blood pH was 7.14 and base excess was -12.7 mmol/l. The tenth percentile for pH in umbilical venous blood was 7.23 and base excess was -10.2 mmol/l. Increase of acidemia was seen in the following order: optimal pregnancy and labor, spontaneous vertex delivery, multiparity, primiparity, instrumental and breech delivery. Percentiles of umbilical cord blood gases could serve as an index for the standard of obstetrical care in addition to perinatal mortality and other measures of perinatal morbidity.

Perinatal data on 76 twin pregnancies demonstrated a significantly (P less than 0.01) lower Apgar score and acidemia in the umbilical artery for the second twin. Factors such as female sex, prematurity, low birth-weight and instrumental delivery accounted for this difference (P less than 0.05 or P less than 0.01). These differences were not found for parity, pregnancy complications and time interval. Using electronic fetal surveillance, expert personnel and rapid resuscitation the neonatal depression could be reversed rapidly, as demonstrated in capillary heel blood. Perinatal mortality was 2-3-times higher than for singletons but perinatal morbidity fell in the range for singletons and was not due to the short-lasting asphyxia during birth.

The obstetrical policy during labor at two University clinics in Nottingham (United Kingdom) and Nijmegen (The Netherlands) was investigated prospectively and simultaneously during a period of three months (1984). At the University of Nijmegen the obstetrical population tended to be more 'pathologic', and less intervention during labor was observed for early amniotomy, pain relief, induction and augmentation of labor. The pH in umbilical arterial blood was as a mean 0.01 unit lower in Nijmegen than in Nottingham. The validity of electronic fetal monitoring appeared to be higher in Nijmegen. It is concluded that data on the neonate probably cannot give an answer in favor of one of these policies. Parenthood information could give more conclusive evidence.

Blood loss during Caesarean section is mainly due to the hysterotomy. A new technique to reduce this blood loss has been evaluated in a prospective controlled clinical trial in 89 patients. The operation technique was standardized according to Joel-Cohen. In the control group (n = 45) the low transversal incision was enlarged by scissors in an upward swing, in the staple group (n = 44) the incision was enlarged by introducing the poly CS 57 instrument with absorbable staples. A double row of staples sealed blood vessels and secured the three uterine layers just before the instrument's blade cut the uterine wall. The two groups were comparable as to the indications for the CS, first or repeat CS, primary or secondary CS, maternal age and parity. The duration of the operation, postoperative complications and hospital stay was equal. However, the blood loss in the 'staple' group was significantly less than in the control group. The conclusions are that this new technique reduced blood loss during Caesarean section, and moreover, it appeared to be extremely useful in patients with varicose veins in the lower uterine segment or placenta praevia.

Fetal heart rate decelerations resembling the late deceleration FHR pattern were produced in fetal sheep by periodic occlusion of the maternal common hypogastric artery for 30-60 sec. Transient fetal hypertension also occurred during the occlusions. Alpha-adrenergic blockade with phentolamine eliminated or markedly reduced the hypertensive response. FHR decelerations still occurred intermittently with some occlusions; however, their character was greatly altered. After parasympathetic blockade with atropine, the decelerations were replaced by periodic FHR accelerations during the occlusions. These accelerations were, in turn, eliminated by the beta-adrenergic blocking agent, propranolol. In the presence of combined parasympathetic, alpha- and beta-adrenergic blockade, the FHR remained essentially constant during the hypogastric artery occlusions in non-acidemic fetuses. FHR decelerations persisted after parasympathetic or total autonomic blockade when the fetuses were significantly hypoxic, as judged by depressed arterial blood pH and base excess values. Beat-to-beat variability of the baseline FHR persisted in the face of severe hypoxia and acidosis. These observations demonstrate that reflex mechanisms are involved importantly in the genesis of late deceleration FHR patterns in the acutely hypoxemic fetus, but that direct depression of myocardial rhythmicity becomes a factor as hypoxic acidosis develops.

Changes in the fetal cardiovascular system due to premature closure of the ductus arteriosus are described using a previously validated mathematical model. Results of the simulated closure of the ductus arteriosus are compared with reported results from animal experiments in which the ductus arteriosus was closed pharmacologically with prostaglandin synthetase inhibitors. The computed cardiovascular changes after ductus closure in the model resemble the changes obtained by administration of indomethacin. This suggests that the central cardiovascular effects of indomethacin (insofar as described here) can be completely attributed to closure of the ductus.

The effects of maternal exercise were studied in 20 healthy women with uncomplicated pregnancies. A continuous-wave Doppler ultrasound system was used to record arterial flow velocity waveforms from the ascending vasculature downstream from the uterine artery. The fetal heart rate was monitored with a Doppler ultrasound cardiotocograph. No significant change was found in the uterine blood flow velocity waveform post-exercise, as expressed by the pulsatility index, suggesting absence of change in the uterine vascular bed resistance. The fetal heart rate significantly increased after exercise.

A retrospective study to detect the frequency of lethal lung hypoplasia in 48 cases with prolonged rupture of membranes (greater than 7 days) before 34 weeks' gestation was made. Fourteen infants died (29%), but only four deaths (8.3%) were due to lung hypoplasia. Three infants with lung hypoplasia had their membranes ruptured before 20 weeks' gestation and showed echoscopically a persistent oligohydramnios, as did the one with rupture at 26 weeks. Neither the duration of rupture of membranes nor the gestational age at the time of rupture showed any influence on the occurrence of lung hypoplasia. The rupture of membranes before 20 weeks' gestational age with resulting persistent oligohydramnios will certainly lead to lung hypoplasia.

Routine ultrasonic crown-rump length measurements were retrospectively evaluated in an antenatal clinic using maternal body temperature graphs as reference to ovulatory age. A comparison with the original figures of Robinson is made. Potential errors are discussed. The conclusion is that one should be very careful in interpreting an ultrasonic CRL measurement before 10 weeks menstrual age because of both measurement and operator errors.

The maternal and fetal placental circulation was studied by recording of the blood flow velocity waveforms (FVW) of the uterine and umbilical artery (UFVW and UmbFVW) in 99 pregnant women. The FVW was quantitated by the Pulsatility-Index (PI). By analysing the UFVWs as well as the UmbFVWs, it was possible to define four groups of patients, based on normal versus abnormal PI on either side of the placenta. The group with abnormal FVWs on both sides of the placental bed showed the highest percentage of pathological phenomena. Uterine and/or umbilical artery FVW analysis was not sensitive in the prediction of small for gestational age (SGA), whereas it was a sensitive method for the prediction of fetal distress (FD) during pregnancy. For the latter, our data suggested that at a chosen specificity of 95%%. FVW analysis on both sides of the placental bed was more sensitive than separate UFVW or UmbFVW analysis.

The preejection period (PEP) of the fetal cardiac cycle was studied in the chronically instrumented fetal lamb. A specially constructed device permitted the occlusion of either both umbilical veins, or of both umbilical arteries, or of the total umbilical cord. A prolongation of the PEP together with an increase in blood pressure was a consistent finding during any type of cord occlusion. In poorly oxygenated fetal lambs a two-step increase in the duration of the PEP was observed during the occlusion. It was accompanied by a simultaneous two-step increase in fetal arterial blood pressure. A correlation was found between the steady-state fetal pO2 before the occlusion and the increase in fetal arterial diastolic blood pressure during the blockade of the umbilical circulation. During occlusion the main determining factors of the PEP prolongation appear to be the increase in afterload and the decrease in preload of the fetal heart. The second step in the prolongation of the PEP during the occlusions in poorly oxygenated fetal lambs is attributed to a chemoreceptor-induced reflex, resulting in a redistribution of cardiac output in the fetal lamb.

Electrocortical activity (ECoG), tracheal pressure and nuchal muscle activity were recorded in utero in 8 chronically hyperglycemic and 10 control unanesthetized fetal lambs to investigate the effects of chronic hyperglycemia on fetal electrocortical activity states. The chronically hyperglycemic state, induced by alloxan administered to the ewes, existed for at least 40 days prior to the experiments. The mean duration of episodes of high voltage (HV) ECoG was significantly increased in the hyperglycemic group (mean +/- SD: 21.8 +/- 9.2 min) compared with the control group (14.8 +/- 3.3 min), but the incidence of low voltage (LV) ECoG was not different between the groups. ECoG power spectra were not different between the groups. During LV ECoG, the proportions of time with neck movements were significantly less in the hyperglycemic than in the control group. No difference in percentages of time with long neck muscle activity was seen during the HV state in both groups. The incidence of breathing movements was equal in both groups, during HV as well as LV ECoG. No differences in breathing interval were observed.

For the assessment of behavioural states in the human fetus, the fetal heart rate (FHR) pattern is one of the state variables. A statistical method is described to classify FHR patterns. FHR recordings were made between 38 and 40 wk gestation. The tachogram was averaged over 3-s intervals. For FHR segments of 3 min duration the parameters of an autoregressive-moving average (ARMA) model were estimated. Simulated FHR patterns, generated by using these estimated ARMA parameters, resembled real recordings. The ARMA parameters were used as features for a retrospective classification of the FHR segments, using a linear discriminant function. The classification by the above method was compared with an independent visual classification of the FHR patterns. The computer/observer classification agreement was 85% (kappa = 0.70). These data were compared with classification results for neonatal heart rate segments. For prospective classification of FHR patterns a moving discriminant function was introduced.