Decrease In Fetal Heart Rate Research Articles

Amniotic fluid embolism rescued using venoarterial extracorporeal membrane oxygenation without initial anticoagulation: A case report and literature review.

Amniotic fluid embolism (AFE) is a fatal obstetric condition that often rapidly leads to severe respiratory and circulatory failure. It is complicated by obstetric disseminated intravascular coagulation (DIC) with bleeding tendency; therefore, the introduction of venoarterial extracorporeal membrane oxygenation (VA-ECMO) is challenging. We report the case of a patient with AFE requiring massive blood transfusion, rescued using VA-ECMO without initial anticoagulation. A 39-year-old pregnant patient was admitted with a complaint of abdominal pain. An emergency cesarean section was performed because a sudden decrease in fetal heart rate was detected in addition to DIC with hyperfibrinolysis. Intra- and post-operatively, the patient had a bleeding tendency and required massive blood transfusions. After surgery, the patient developed lethal respiratory and circulatory failure, and VA-ECMO was introduced. Based on the course of the illness and imaging findings, the patient was diagnosed with AFE. By controlling the bleeding tendency with a massive transfusion and tranexamic acid administration, using an antithrombotic ECMO circuit, and delaying the initiation of anticoagulation and anti-DIC medication until the bleeding tendency settled, the patient was managed safely on ECMO without complications. By day 5, both respiration and circulation were stable, and the patient was weaned off VA-ECMO. Mechanical ventilation was discontinued on day 6. Finally, she was discharged home without sequelae. VA-ECMO may be effective to save the lives of patients who have AFE with lethal circulatory and respiratory failure. For safe management without bleeding complications, it is important to start VA-ECMO without initial anticoagulants and to administer anticoagulants and anti-DIC drugs after the bleeding tendency has resolved.

Fetal heart rate changes and labor neuraxial analgesia: a machine learning approach

BackgroundNeuraxial labor analgesia has been associated with fetal heart rate changes. Fetal bradycardia is multifactorial, and predicting it poses a significant challenge to clinicians. Machine learning algorithms may assist the clinician to predict fetal bradycardia and identify predictors associated with its presentation.MethodsA retrospective analysis of 1077 healthy laboring parturients receiving neuraxial analgesia was conducted. We compared a principal components regression model with tree-based random forest, ridge regression, multiple regression, a general additive model, and elastic net in terms of prediction accuracy and interpretability for inference purposes.ResultsMultiple regression identified combined spinal-epidural (CSE) (p = 0.02), interaction between CSE and dose of phenylephrine (p < 0.0001), decelerations (p < 0.001), and the total dose of bupivacaine (p = 0.03) as associated with decrease in fetal heart rate. Random forest exhibited good predictive accuracy (mean standard error of 0.92).ConclusionUse of CSE, presence of decelerations, total dose of bupivacaine, and total dose of vasopressors after CSE are associated with decreases in fetal heart rate in healthy parturients during labor. Prediction of changes in fetal heart rate can be approached with a tree-based random forest model with good accuracy with important variables that are key for the prediction, such as CSE, BMI, duration of stage 1 of labor, and dose of bupivacaine.

Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep.

Fetal heart rate (FHR) deceleration is the most common change seen during labor. The role of the autonomic nervous system in regulating the fetal cardiovascular response during multiple uterine contractions has been well-established. However, the mechanism underlying the hemodynamic response remains unclear and the specific reflex that mediates the cardiovascular modifications is still controversial. This study aimed to determine the role of the sympathetic and parasympathetic systems on fetal hemodynamics in complete cord occlusion. Chronically instrumented fetal sheep were randomized to receive an intravenous injection of atropine 2.5 mg (n = 8), propranolol 5 mg (n = 7), atropine and propranolol (n = 7), or a control protocol (n = 9), followed by three episodes of 1-minute umbilical cord occlusion repeated every 5 minutes. Cord compression induces a rapid decrease in the FHR and a rapid increase in MAP. The decrease in FHR is caused by an increase in parasympathetic activity, (atropine and atropine-propranolol abolish the FHR response to the occlusion). The change in FHR during occlusion was not modified by propranolol injection, showing no effect of sympathetic tone. The increase in MAP during occlusion was similar in the four protocols. After releasing occlusion, the FHR was still lower than that at baseline due to a sustained parasympathetic tone. Suppression of the parasympathetic output to the cardiovascular system unmasks an increase in the FHR above baseline values. The lower FHR with the propranolol protocol further supports an increase in myocardial β-adrenoceptor stimulation after cord release. The increase in MAP after cord release was similar in the four protocols, except after the early stage of interocclusion period in atropine protocol. Four minutes after cord release, the FHR returned to baseline irrespective of the drugs that were infused, thereby showing recovery of ANS control. Blood gases (pH, PaCO2, PaO2) and plasma lactate concentrations was similar between the four protocols at the end of three applications of UCO. Complete cord compression-induced deceleration is likely due to acute activation of parasympathetic output. β-adrenoceptor activity is involved in the increase in FHR after cord release. Understanding the reflexes involved in FHR deceleration may help us understand the mechanisms underlying fetal autonomic adaptation during cord occlusion.

Exploring fetal response to acidosis in ewes: Choosing an adequate experimental model

IntroductionKnowledge of fetal physiology during labor has been largely generated from animal models. Our team recently developed a new index to assess parasympathetic activity using different experimental protocols to obtain acidosis. The objective of the present study was to discuss the different protocols and to review other models proposed in the literature. Material and methodsPregnant ewes underwent a surgical procedure at the 123±2 days gestational age (term=145 days). Three experimental protocols were used: protocol A consisted of 25%, 50% and 75% umbilical cord occlusion (UCO) for 20min. Protocol B consisted of partial 75% UCO until reaching a pH<7.10. Protocol C consisted of brief, repetitive complete occlusion until severe acidosis occurred. Hemodynamic and blood gas parameters were compared to those of the stability period before UCO. ResultsProtocol A led to a progressive response depending on the degree of occlusion (decrease in fetal heart rate, arterial hypertension and pH). Protocol B led to severe acidosis, although the duration of UCO varied per animal. Protocol C also progressively led to acidosis. We observed high inter individual variability in the acidosis response. ConclusionPregnant ewes are a relevant model for exploring fetal response to acidosis. The frequency of UCO and partial or complete occlusion should be adapted to the expected effects. Knowledge of these protocols is important to respect ethical guidelines and to reduce the required number of animals. Moreover, it is important to consider the high individual variability of the acidosis response in the interpretation of the results.

Maternal-fetal acute responses to two moderate-intensity exercise types: a randomized clinical trial

Objective: This study aims to compare maternal and fetal responses during two physical exercise types.&#x0D; Design: A randomized clinical trial compared 120 pregnant women, gestational age of 35-37 weeks, 56 exercising on a stationary bicycle (Group A) and 64 on a treadmill (Group B).&#x0D; Methods: Participants were monitored for three 20-minute phases: resting, exercise and recovery. Fetal heart rate (FHR) and maternal heart rate (MHR) were monitored. Glucose and lactate levels were evaluated at rest and during exercise.&#x0D; Results: After the beginning of exercise, maximum lactate (L) levels were reached at 20 minutes and never exceeded 4 mmol/l. FHR decreased by 22 bpm during exercise in relation to resting values, irrespective of the exercise type (p&lt;0.001). Comparing the exercise types, the incidence of bradycardia after 10’ was 23.2% in Group A and 35.9% in Group B (p&gt;0.05), increasing at 20’ to 32% and 40.6%, respectively, (p&gt;0.05). The FHR decrease during exercise was accompanied by a simultaneous increase in its variability (p&lt;0.001), nevertheless a rapid return to resting values was observed shortly after exercise end. Glucose decreased in both groups irrespective of the exercise type (85 mg/dl at rest; 79 mg/dl during exercise and 81 mg/dl during recovery; p&lt;0.001). There were no hypoglycemia cases.&#x0D; Conclusions: FHR variability increase and the rapid return to resting values after exercise suggests that the FHR fall and the presence of bradycardia during exercise is the fetal physiologic response to blood flow redistribution, with maintenance of fetal well-being.&#x0D; Key-words: Exercise; fetal heart rate; glucose; maternal heart rate; pregnancy&#x0D; Clinical Trial Registration: ClinicalTrials.gov, www.clinicaltrials.gov, NCT01383889.

Efficacy of first-trimester ultrasound parameters for prediction of early spontaneous abortion.

To assess first-trimester ultrasound measurements for the prediction of early spontaneous abortion. In a prospective observational study in Jamshedpur, India, women with singleton pregnancies of 42-76days were enrolled between November 2014 and April 2016. Inclusion criteria were spontaneous conception, embryonic cardiac activity, and regular menstrual cycle. Fetal crown-to-rump length (CRL), gestational sac diameter (GSD), yolk sac diameter (YSD), and fetal heart rate (FHR) were measured by transvaginal ultrasonography. Ultrasonography was repeated at 12weeks and beyond to determine pregnancy continuation. Among 800 women, 140 (17.5%) experienced early spontaneous abortion. CRL, GSD, and FHR values below the 5th percentile (odds ratio [OR] 26.48, 26.94, and 100.63, respectively), and YSD above the 95th percentile (OR 1.04) were predictors of early abortion. Normal YSD did not reduce the risk of abortion if the other three parameters were below the 5th percentile (OR 34.27). For every 10-bpm decrease in FHR below 130, there was 26.7% increased risk of abortion. GSD-CRL difference of less than 5mm was associated with a higher likelihood of abortion (OR 4.88). First-trimester ultrasound measurements are predictors of early abortion. Risk assessment tables based on combinations of abnormal measures might improve prediction rates.

Fetal heart rate variation after corticosteroids for fetal maturation

IntroductionSeveral studies report a decrease of fetal heart rate (FHR) short-term variation (STV) after corticosteroids for improvement of fetal maturity and advice not to deliver a fetus for low STV within 2–3days after corticosteroids. However, literature is not unanimous in this respect. This study intends to asses STV longitudinally after corticosteroid administration. Material and methodsA retrospective cohort study in a tertiary perinatal centre from 2009 to 2015 included all women who had been treated with corticosteroids at gestational age of 26–34 weeks, had a computerized cardiotocography (cCTG) before and after medication and did not deliver within 48h. FHR and STV were stratified over 12-h periods and compared before and after corticosteroids. Women with imminent preterm labour (including PPROM) and women with placental problems (fetal growth restriction (FGR) or preeclampsia) (PE) were analysed separately. The effect of co-medication and gestational age was assessed. ResultsThe study included 406 women, 211 with imminent preterm labour, 195 with FGR-PE. After corticosteroids STV increased 1–2ms (median 1.4; IQR 0.1–3.1) during the first 36h after start of corticosteroids. Thereafter a small decrease of less than 1ms (median −0,6; IQR −1.6 to 0.3) compared to before CC was seen. ConclusionsThe most conspicuous effect of corticosteroids is a short term increase of STV and decrease of FHR. A slight decrease after 48–71h is possible, but abnormally low values should be considered as a sign of fetal distress. The clinical guidance, given by some, not to intervene because of a low STV after corticosteroids appears invalid.

Pregnancy distress gets under fetal skin: Maternal ambulatory assessment & sex differences in prenatal development.

Prenatal maternal distress is associated with an at-risk developmental profile, yet there is little fetal evidence of this putative in utero process. Moreover, the biological transmission for these maternal effects remains uncertain. In a study of n = 125 pregnant adolescents (ages 14-19), ambulatory assessments of daily negative mood (anger, frustration, irritation, stress), physical activity, blood pressure, heart rate (every 30 min over 24 hr), and salivary cortisol (six samples) were collected at 13-16, 24-27, 34-37 gestational weeks. Corticotropin-releasing hormone, C-reactive protein, and interleukin 6 from blood draws and 20 min assessments of fetal heart rate (FHR) and movement were acquired at the latter two sessions. On average, fetuses showed development in the expected direction (decrease in FHR, increase in SD of FHR and in the correlation of movement and FHR ("coupling")). Maternal distress characteristics were associated with variations in the level and trajectory of fetal measures, and results often differed by sex. For males, greater maternal 1st and 2nd session negative mood and 2nd session physical activity were associated with lower overall FHR (p < .01), while 1st session cortisol was associated with a smaller increase in coupling (p < .01), and overall higher levels (p = .05)-findings suggesting accelerated development. For females, negative mood, cortisol, and diastolic blood pressure were associated with indications of relatively less advanced and accelerated outcomes. There were no associations between negative mood and biological variables. These data indicate that maternal psychobiological status influences fetal development, with females possibly more variously responsive to different exposures.

Ultrasonographic fetal parameters and neonatal survival in somatic cell nuclear transfer–derived beef calves

The objectives of this study were to identify prognostic indicators of calf survival in SCNT-derived beef calves. Ultrasonographic parameters of fetal well-being and development, maternal clinical parameters, and neonatal parameters were evaluated as predictors of calf survival in cows carrying SCNT-derived beef fetuses (n = 38). Calf survival was 61.5% (88.2% female and 40.9% male calves; P = 0.0026). Cow respiratory rate and cow temperature were significantly greater in the nonsurviving (NS) group 1 week prepartum. In surviving (S) calves, fetal heart rate (FHR) decreased during the last 2 weeks of gestation (P < 0.01). However, this final deceleration was not observed in NS calves, resulting in higher FHRs in this group (P < 0.0001). Fetal movement and fluid scores did not differ with calf classification. Mean amniotic fluid depth was smaller in S (5.5 ± 0.7 cm) than NS (8.7 ± 1.4 cm) calves (P = 0.0398). However, mean allantoic fluid depth did not differ (P = 0.6120). There was a significant association between the body weight of calf and the diameter of the fetal aorta (P = 0.0115; r2 = 0.3762). Surviving calves were lighter at birth (P = 0.0028) and were born later (P = 0.007) than NS calves. Calves born vaginally had a smaller fetal aorta (2.1 ± 0.1 cm vaginal and 2.4 ± 0.1 cm Cesarean) (P = 0.0487) and a lighter birth weight (41.4 ± 4.2 kg vaginal and 60.4 ± 2.1 kg Cesarean) (P = 0.0001) than calves born by Cesarean. Also, calves that underwent spontaneous labor (52.2% S and 0% NS; P = 0.0029) had a lighter birth weight (44.9 ± 3.8 kg) than calves that did not initiate labor (61.6 ± 2.2 kg) (P = 0.0004). Frequent ultrasonographic fetal monitoring allowed identification of differences between S and NS calves. Calves without a final decrease in FHR or with a large aortic diameter were more likely to require a Cesarean because of failure to initiate labor or fetomaternal disproportion. Parameters of fetal well-being and development during the last 3 weeks of gestation were first described in SCNT-derived beef calves.

Evaluation of the Fetal Heart Rate during Amniocentesis in Fetuses with Normal and Abnormal Karyotype

Abstract Introduction. We monitored the fetal heart rate (FHR) during amniocentesis in fetuses at 16-22 weeks of gestation and investigated whether an abnormal FHR was associated with chromosomal abnormalities. Methods. This prospective study involved 600 women at 16-22 weeks of gestation who underwent genetic amniocentesis. The FHR, expressed as beats for minute, was recorded before (FHR1), immediately after (FHR2) and 60 min after (FHR3) the invasive procedure. Structural malformations detected by ultrasound and multiple pregnancy were excluded from the study. Results. Chromosomal abnormalities have been diagnosed in 27 fetuses. Mean FHR decrease after amniocentesis has been observed in normal and in abnormal fetuses. The mean variation during amniocentesis was significant in both groups (P&lt;0.01). The comparison between the mean FHR of the two groups showed no differences in FHR1 and FHR2 (P&gt;0.05) but a significant difference in FHR3 (P&lt;0.05). Conclusion. The FHR decreased after amniocentesis; the decrease was larger in chromosomally abnormal fetuses than in normal fetuses. This difference in heart rate reaction to amniocentesis might be due to cardiac defects or developmental delay associated with the abnormal karyotype.

Monitoring Fetal Electrocortical Activity during Labour for Predicting Worsening Acidemia: A Prospective Study in the Ovine Fetus Near Term

BackgroundSevere fetal acidemia during labour with arterial pH below 7.00 is associated with increased risk of hypoxic-ischemic brain injury. Electronic fetal heart rate (FHR) monitoring, the mainstay of intrapartum surveillance, has poor specificity for detecting fetal acidemia. We studied brain electrical activity measured with electrocorticogram (ECOG) in the near term ovine fetus subjected to repetitive umbilical cord occlusions (UCO) inducing FHR decelerations, as might be seen in human labour, to delineate the time-course for ECOG changes with worsening acidemia and thereby assess the potential clinical utility of fetal ECOG.Methodology/Principal FindingsTen chronically catheterized fetal sheep were studied through a series of mild, moderate and severe UCO until the arterial pH was below 7.00. At a pH of 7.24±0.04, 52±13 min prior to the pH dropping <7.00, spectral edge frequency (SEF) increased to 23±2 Hz from 3±1 Hz during each FHR deceleration (p<0.001) and was correlated to decreases in FHR and in fetal arterial blood pressure during each FHR deceleration (p<0.001).Conclusions/SignificanceThe UCO-related changes in ECOG occurred in advance of the pH decreasing below 7.00. These ECOG changes may be a protective mechanism suppressing non-essential energy needs when oxygen supply to the fetal brain is decreased acutely. By detecting such “adaptive brain shutdown,” the need for delivery in high risk pregnant patients may be more accurately predicted than with FHR monitoring alone. Therefore, monitoring fetal electroencephalogram (EEG, the human equivalent of ECOG) during human labour may be a useful adjunct to FHR monitoring.

Evaluation of fetal heart rate variation during amniocentesis: correlation with fetal karyotype

Objective. We monitored the fetal heart rate (FHR) during amniocentesis in fetuses at 16–18 weeks of gestation and investigated whether an abnormal FHR is associated with chromosomal abnormalities.Methods. This prospective study involves 807 women at 16–18 weeks of gestation who underwent genetic amniocentesis. The FHR, expressed as beats for minute, is recorded before (FHR1), immediately after (FHR2) and 60 min after (FHR3) the invasive procedure. Structural malformations detected by ultrasound and multiple pregnancy are excluded from the study.Results. Chromosomal abnormalities have been diagnosed in 27 fetuses. A mean FHR decrease after amniocentesis has been observed in normal and in abnormal fetuses. The mean variation during amniocentesis is significant in both groups (P < 0.01). The comparison between the mean FHR of the two groups shows no differences in FHR1 and FHR2 (P > 0.05) but a significant difference in FHR3 (P < 0.05).Conclusion. The FHR decreases after amniocentesis; the decrease is larger in chromosomally abnormal fetuses than in normal fetuses. This difference in heart rate reaction to amniocentesis might be due to cardiac defects or developmental delay associated with the abnormal karyotype.

Fetal Ventricular Diastolic Filling Characteristics in a Primate Model: The Role of Fetal Heart Rate and Pulmonary Vascular Impedance

We hypothesized that fetal ventricular diastolic filling characteristics are related to fetal heart rate (FHR) and pulmonary vascular impedance. Rhesus monkeys underwent Doppler ultrasonography at near-term gestation. Tricuspid (TV) and mitral valve (MV) blood velocity waveforms were used to calculate maximum velocity (V-max) and velocity time integral (VTI) E/A ratios (early filling/ventricular filling during atrial contraction) at baseline and during maternal hyperoxygenation. Right pulmonary artery (RPA) pulsatility indices (PIs) and FHR were measured. Hyperoxgenation significantly decreased FHR and RPA PI. The TV V-max and the MV VTI E/A ratios increased significantly and correlated with a decrease in FHR but not with a decrease in RPA PI. The TV and MV A-wave V-max decreased during hyperoxygenation and their decrease correlated significantly with a drop in FHR. Fetal ventricular diastolic filling characteristics are related to FHR but not to pulmonary vascular impedance.

Maternal factors implicated in fetal bradycardia after combined spinal epidural for labour pain

Combined spinal epidural analgesia is effective for fast relief of severe labour pain but has been associated with worrisome decreases in fetal heart rate. Since the reasons for this phenomenon remain elusive, some anaesthesiologists may abstain from using this technique. We postulated that factors unrelated to the neuraxial technique could play a role in the decrease in fetal heart rate. To our knowledge, no prospective study has previously looked into this possibility. We collected prospective data on 223 consecutive patients who received combined spinal epidural analgesia (123) or epidural analgesia (100). Maternal blood pressure, analogue pain scores, exogenous infusion of oxytocin, cervical dilatation, maternal age, parity and ethnicity were collected and correlated with the occurrence of decreases in fetal heart rate post combined spinal epidural. Univariate analysis showed a correlation between the incidence of fetal bradycardia and higher maternal pain scores, older maternal age, and combined spinal epidural analgesia. Multivariate analysis revealed that only pain scores and maternal age were independent predictors of fetal bradycardia post neuraxial blockade. Maternal pain scores and older maternal age are factors unrelated to the neuraxial technique that are independent predictors of fetal bradycardia after neuraxial analgesia for labour.

Prenatal predictors of infant temperament

Emerging data suggest that prenatal factors influence children's temperament. In 50 dyads, we examined fetal heart rate (FHR) activity and women's antenatal psychiatric illness as predictors of infant temperament at 4 months (response to novelty and the Infant Behavior Checklist). FHR change during maternal challenge was positively associated with observed infant motor reactivity to novelty (p = .02). The odds of being classified as high versus low motor among fetuses who had an increase in FHR during maternal stress was 11 times those who had a decrease in FHR (p = .0006). Antenatal psychiatric diagnosis was associated with an almost fourfold greater odds of having a high cry reactivity classification (p = .03). There also were modest associations between baseline FHR and maternal reports of infant temperament and between observed temperament and that based on mothers' reports. All of the infant results were found independent of the influence of women's postnatal anxiety. These data indicate that physiological markers of individual differences in infant temperament are identifiable in the fetal period, and possibly shaped by the prenatal environment.

The effects of antenatal betamethasone administration on fetal heart rate and behaviour depend on gestational age

Objective: We previously reported decreases in fetal heart rate (FHR) variability and body and breathing movements after maternal betamethasone administration. We now test the hypothesis that fetal responsiveness to betamethasone depends on the gestational age at which glucocorticoid therapy is started. Design of the study: 1-h recordings of FHR ( n=350) and fetal movements ( n=310) made during a 5-day period (days 0–4) were available for analysis. The recordings had been obtained from 63 pregnant women at high risk for preterm delivery who received betamethasone (two doses of 12 mg 24 h apart) between 26 and 34 weeks' gestational age (wGA). The response to betamethasone, i.e. the direction and magnitude of change in FHR and movement parameters compared with baseline (day 0), was studied in relation to gestational age at drug administration. Results: Fetuses exposed to betamethasone at 29–34 wGA showed a decrease in FHR on day 1 (indicative of baroreceptor reflex), and reduced breathing activity and prolonged episodes of quiescence with a concomitant decrease in body movements on days 1 and 2. However, these changes were not observed if betamethasone administration occurred at 26–28 wGA. Betamethasone-induced reductions in FHR variability were similar in young and older fetuses. Conclusions: Age-related differential responsiveness to betamethasone was found for all studied fetal processes (body and breathing movements, FHR, and quiescence), except FHR variability. Our results suggest ontogenic changes in the mechanisms presumed to underlie these processes (glucocorticoid receptor (GR) maturation, cardiovascular and neuro-endocrine development).

Flecainide in the intrauterine treatment of fetal supraventricular tachycardia.

To assess the efficacy of flecainide in the intrauterine treatment of fetal supraventricular tachycardia (SVT) with 1 : 1 atrioventricular conduction. Twenty fetuses (21-35 weeks of gestation) with SVT ranging between 215 and 280 bpm were analyzed retrospectively. Fetuses received flecainide and digoxin as either first, second or third line therapy. Intracardiac blood flow, venous Doppler waveforms and cardiotocograms were evaluated before and after drug induced conversion to sinus rhythm. After initiation of combined flecainide and digoxin therapy, the median time interval until final conversion to sinus rhythm was 5 days (range, 0-14 days). The majority of fetuses (n = 15; 75%) converted to sinus rhythm within 7 days of treatment, whereas the remaining five (25%) showed initial reduction of the heart rate to 160-215 bpm over several days, with restoration of a triphasic venous blood flow pattern before late conversion within 7-14 days after initiation of flecainide treatment. One of these fetuses showed a decrease in fetal heart rate to 160-190 bpm without conversion to sinus rhythm but with resolution of hydrops. All fetuses survived. Flecainide is safe and highly effective in the intrauterine treatment of hydropic fetuses with supraventricular tachycardia. Conversion into sinus rhythm can be expected 72 h after initiation of therapy but may take up to 14 days. Therefore therapy should be continued beyond 72 h, especially when an initial decrease of fetal heart rate is observed which may represent an early therapeutic response.

Adaptation of cardiovascular responses to repetitive umbilical cord occlusion in the late gestation ovine fetus.

1. The impact of repeated umbilical cord occlusion on the normal maturation of fetal heart rate (FHR) and mean arterial pressure (MAP) and the cardiovascular responses to successive umbilical cord occlusion was investigated over a 21 day period in the latter part of gestation. 2. Fifteen chronically instrumented sheep (control group n = 6; occlusion group n = 9) were studied for 21 days (113-133 days of gestation, term = 145 days) with umbilical cord occlusions (90 s duration) performed every 30 min for 1-4 h each day. On days 1, 9 and 18, FHR, FHR variation and MAP were monitored continuously and fetal arterial blood gases, pH and metabolites were measured at predetermined intervals. The baroreflex response to 75-100 microg phenylephrine (I.V.) was tested on days 1 and 18. 3. Basal FHR decreased (DeltaFHR: control, 34.6 +/- 3.6 beats x min(-1); occlusion, 36.9 +/- 2.7 beats x min(-1)) and MAP increased (DeltaMAP: control, 3.1 +/- 1.7 mmHg; occlusion, 5.2 +/- 2.1 mmHg) to a similar extent in control and occlusion groups between days 1 and 21 of the study. There was a small decline in FHR variation over the 21 day study in occlusion, but not control, group fetuses. 4. The magnitude of the fall in FHR decreased and the rise in MAP increased, despite similar changes in blood gases in response to umbilical cord occlusion, over the course of the 21 day study. Despite a significant decline in the ratio of DeltaFHR to DeltaMAP on days 9 and 18 compared to day 1, there was no difference between control and occlusion groups in baroreflex sensitivity. However DeltaFHR/DeltaPO2, an index of chemoreceptor sensitivity, had decreased by day 9 and 18 compared to day 1. 5. The cardiovascular responses to umbilical cord occlusion are altered with repetitive occlusions during the latter part of gestation, with a decrease in DeltaFHR/DeltaMAP, which does not involve changes in baroreflex sensitivity, but may involve changes in chemoreceptor sensitivity. However, repeated umbilical cord occlusion appears to have no impact on baseline cardiovascular control since there was no change in the normal maturational decrease in FHR and rise in MAP.

Effects of morphine and naloxone on fetal heart rate and movement in the pig.

To test the hypothesis that an increasing opioid tonus is involved in decreases in fetal heart rate (FHR) and movement (FM) during late gestation, we studied the effects of intravenous bolus injections of morphine (1 mg) and naloxone (1 mg) on FHR and FM in the fetal pig. Twenty-one fetuses (1 per sow) were catheterized at 90-104 days of gestation (median 100 days). Recordings of FHR (electrocardiograph or Doppler-derived signals) and FM (ultrasonography) were made from 15 min before to 45 min after treatment. Morphine administration significantly decreased FHR, but it increased FHR variation and forelimb movements (LM). LM were clustered, and this stereotyped behavior has never before been observed in any mammalian fetus. Naloxone administration increased gross body movements and FHR without significant changes in FHR variation. It is concluded that FHR and motility are under opioidergic control in the pig fetus. Both morphine and naloxone induce hypermotility, suggesting that naloxone does not act as a pure opioid antagonist in the fetal pig.

Magnesium Sulfate and Fetal Plasma Concentrations of Epinephrine, Norepinephrine, and Vasopressin in Response to Acute Hypoxemia in Goats

We measured fetal plasma concentrations of epinephrine, norepinephrine, and vasopressin during acute hypoxemia in goats and tested whether hypermagnesemia altered these endocrine responses. Five chronically catheterized goat fetuses at 124-129 days' gestation were used. After 4 hours of infusion (magnesium or vehicle as controls), 30 minutes of hypoxemia was induced by infusing nitrogen gas through a maternal tracheal catheter. Fetal plasma concentrations of epinephrine, norepinephrine, and vasopressin were measured before and during hypoxemia. Both magnesium sulfate and vehicle infusions were performed in each animal. Repeated-measures analysis of variance (ANOVA) and two-way ANOVA with post hoc test were used to determine statistical significance. During hypoxemia, fetal PO(2) decreased significantly from 30 to 14 mmHg with no significant changes in fetal pH or PCO(2) in both groups. Fetal heart rate was reduced significantly by hypoxemia, but to a lesser extent in the magnesium group (change in decrease in fetal heart rate: 41 beats per minute [bpm] in controls versus 26 bpm with magnesium). Mean blood pressure did not change significantly during hypoxemia in both groups. Fetal plasma concentrations of epinephrine, norepinephrine, and vasopressin significantly increased from the prehypoxemic values both with magnesium and in controls. There were no significant differences in these hormone concentrations between magnesium and the controls. Magnesium sulfate had no effect on fetal plasma concentrations of vasopressin, epinephrine, and norepinephrine during acute hypoxemia.