oxytocin and Fetal-Hypoxia

Both mother and fetus have the remarkable ability to adapt to conditions of chronic hypoxia during the course of gestation. One of these adaptations appears to be mechanisms that prevent premature delivery despite the chronic stress of hypoxia. Our studies in the chronically hypoxic sheep revealed that the fetal adrenal is less responsive to ACTH stimulation. This in turn may prevent a premature rise in cortisol that would normally trigger labor and delivery. In the rat, the myometrium is affected with a decrease in contractile sensitivity to oxytocin following chronic hypoxia. This response is mediated by a significant reduction in myometrial oxytocin receptors. Our preliminary studies have also suggested that this blunting of myometrial responsiveness also occurs in the chronically hypoxic sheep. Taken together, these data indicate an adaptive response by both mother and fetus to prevent preterm delivery in the face of a chronic stress.

Topics: Adaptation, Physiological; Adrenocorticotropic Hormone; Animals; Female; Fetal Hypoxia; Humans; Hydrocortisone; Hypothalamo-Hypophyseal System; Maternal-Fetal Exchange; Obstetric Labor, Premature; Oxytocin; Pituitary-Adrenal System; Pregnancy; Rats; Sheep; Stress, Physiological; Uterine Contraction

During the past few years enormous progress has been made in the understanding of the molecular mechanisms involved in parturition; however, the answer to the fundamental question of how labor is initiated remains elusive. This is a very important question because alterations in the timing of birth (preterm and post-term deliveries) are associated with much of perinatal morbidity and mortality. Currently available treatments for preterm labor are not clearly effective. Prevention of preterm delivery by home uterine monitoring has been proposed; however, the value of this technique has not been conclusively shown. A variety of substances have been implicated in the genesis of labor, including oxytocin, prostaglandins, cytokines, and endothelin. The role of infection in preterm labor has also been extensively studied, but it seems clear that a relatively small percentage of preterm labor is caused by infection. Attention has also focused on the role of estrogen and progesterone, and the possible uses of progesterone antagonists in the induction of labor. A better understanding of the relationship of intrauterine hypoxia and preterm delivery may also help us in establishing treatment and prevention strategies.

Topics: Cardiotocography; Cytokines; Endothelins; Estrogens; Female; Fetal Growth Retardation; Fetal Hypoxia; Fibronectins; Gap Junctions; Home Care Services; Humans; Labor, Obstetric; Molecular Biology; Obstetric Labor, Premature; Oxytocin; Pregnancy; Progesterone; Prostaglandins; Uterine Contraction

The authors have studied the recent literature as well as the conclusions reached at the FIGO Congress in Berlin in 1985 to define rigorous criteria for interpreting the three principal methods that are carried out for antepartum monitoring. These are the non-stress test (NST), the oxytocin test (OCT) and the biophysical score (BPS). The point out the usefulness and the reliability of the NST as a screening technique for hypoxia in utero and also how necessary it is to use more sensitive tests like OCT ou BPS to work out the degree to which the fetus is affected. The way the cases should be handled clinically according to the results of these tests is described.

Topics: Female; Fetal Distress; Fetal Heart; Fetal Hypoxia; Fetal Monitoring; Fetal Movement; Fetus; Heart Rate; Humans; Oxytocin; Pregnancy; Risk

Advance in fetal sheep surgery has allowed investigation of vasopressin physiology at the end of gestation (100 to 140 days). In the fetus of that age, vasopressin is present in the pituitary and in the blood. The hormonal secretion is stimulated by hypotensive and hyperosmolar stimulus. Hypoxemia is also reported as being a potent stimulus of vasopressin secretion and may have an important effect on blood pressure control.

Topics: Animals; Arginine Vasopressin; Blood; Female; Fetal Hypoxia; Fetus; Hemorrhage; Osmolar Concentration; Oxytocin; Pituitary Gland, Posterior; Placenta; Pregnancy; Sheep; Vasotocin

Oxytocin is used to induce and control parturition; nevertheless, an increase in uterine contractions decreases blood flow and gaseous exchange through the uterus predisposing to intra-partum mortality in pigs. The objective of the present study was to evaluate the effect of different oxytocin administration routes on myometrial activity, fetal intrauterine hypoxia and postnatal asphyxia in crated farrowing sows. Yorkshire x Landrace hybrid sows (n = 300), that were approaching the time of parturition, were randomly assigned into six groups. Each group included 50 sows, 10 for each of the parities from one to five. A 40-IU oxytocin dosage was administered by intramuscular (IM), or intravulvar (IVU) routes, or 20 IU was administered via intravenous (IV) route. Groups 1 (G1), 3 (G3) and 5 (G5) were administered 0.9% saline solution (NaCl) IM, IVU and IV, respectively, whereas groups 2 (G2), 4 (G4) and 6 (G6) were treated with oxytocin IM, IVU and IV, respectively. There was a significantly (P < 0.05) greater number of intra-partum stillbirths (IPS) for the oxytocin treatments, as compared with the control groups, especially with the IVU and IV routes; a lesser number of IPS and lesser IPS with broken umbilical cords was observed with the IM administration route. Oxytocin and control IV administration resulted in longer farrowing durations. Administration of IV-oxytocin resulted in a greater number (P < 0.05) of intrauterine distressed neonates compared with its corresponding control and interpreted through dips II, a fetal cardiac frequency deceleration which determines acute fetal suffering. Independent of the route of oxytocin administration, the treatments resulted in twice as many dips II compared with the respective control groups. The use of the cardiotocograph proved to be an excellent tool for establishing the oxytocin response dose in farrowing sows. A greater number of piglets born alive, which had undergone bradycardia, also showed severe acidosis and greater meconium staining in oxytocin-treated sows, indicating that the administration time (at birth of the first piglet) as well as the dosage used were not adequate treatment regimens in the present study. Further studies will be conducted to evaluate different dosages and oxytocin administration timing to determine the most desirable treatment regimen to increase myometrial contractibility without compromising fetal welfare and neonatal survival.

Topics: Animals; Animals, Newborn; Asphyxia; Female; Fetal Death; Fetal Hypoxia; Fetal Monitoring; Fetus; Injections, Intramuscular; Injections, Intravenous; Oxytocics; Oxytocin; Pregnancy; Swine

The objective of the present study was to evaluate in penned sows the effect of two commercial oxytocin products on umbilical cord pathology, degree of asphyxia and intra-partum mortality. This study included 120 sows divided in three groups of 40 animals with eight animals for parities one to five per subgroup, respectively. Group 1 (G(1)) or control received saline solution while oxytocin groups (G(2)) and (G(3)) were injected at the onset of fetal expulsion with two oxytocin products. The doses of oxytocin were as follow: Primiparous sows weighing less than 130 kg received 20 IU; multiparous sows weighing 130-180 g received 30 IU, and those above 250 kg, 40 IU. Piglets born alive and/or dead were classified at birth using a subjective scale based on the degree of meconium staining on skin. Umbilical cords of intra-partum stillbirths (IPS) were classified as adhered or ruptured and subdivided into four categories: without pathological changes, edematous, congested and hemorrhagic. Result analyses revealed significant differences (P < 0.01) between groups 1 and 2, and 1 and 3 regarding the following traits: expulsion interval (min) (X: G(1) 27.7; G(2) 22.6; G(3) 22.2), IPS with a severe stain degree (X: G(1) 0.10; G(2) 0.45; G(3) 0.50), IPS with ruptured umbilical cords (X: G(1) 0.07; G(2) 0.42; G(3) 0.47), and detectable heartbeats in IPS (X: G(1) 0.27; G(2) 0.25; G(3) 0.22). Treatment with oxytocin reduced the duration of the expulsion of the fetus, increased the number of IPS with ruptured umbilical cords and with severe meconium-stain degree and reduced the number of fetuses with inspiration attempts. Furthermore, the use of this hormone increased the need for obstetric assistance due to increased frequency of dystocia.

Topics: Animals; Animals, Newborn; Dystocia; Female; Fetal Death; Fetal Hypoxia; Housing, Animal; Oxytocin; Parity; Pregnancy; Pregnancy Outcome; Rupture, Spontaneous; Swine; Swine Diseases; Umbilical Cord

Intrauterine resuscitative measures are commonly initiated during labor when the fetal heart rate (FHR) pattern is indeterminate or abnormal. The most effective use of these measures is directed at the presumed underlying cause. However, some FHR patterns are nonspecific, while others are such that intrauterine resuscitation will not remedy the situation. The goals of intrauterine resuscitation during labor are, at its best, to reverse any hypoxia that might lead to further deterioration, and at the very least to avoid prolonged periods of indeterminate or abnormal FHR patterns, which may cause unnecessary concern for caregivers and patients and unnecessary operative intervention.

Topics: Erythrocyte Transfusion; Female; Fetal Distress; Fetal Hypoxia; Fetal Monitoring; Fluid Therapy; Heart Rate, Fetal; Humans; Labor, Obstetric; Obstetric Labor Complications; Oligohydramnios; Oxygen; Oxytocin; Pregnancy; Resuscitation; Tocolytic Agents

Tyzio et al. (Reports, 15 December 2006, p. 1788) reported that maternal oxytocin triggers a transient excitatory-to-inhibitory switch of gamma-aminobutyric acid (GABA) signaling during labor, thus protecting the fetal rat brain from anoxic injury. However, a body of evidence supports the possibility that oxytocin is released from the fetal pituitary during delivery, not only from the mother, particularly under conditions of hypoxic stress.

Topics: Animals; Animals, Newborn; Brain; Female; Fetal Hypoxia; Fetus; gamma-Aminobutyric Acid; Hippocampus; Oxytocin; Parturition; Pituitary Gland; Pregnancy; Rats; Signal Transduction

During fetal hypoxia blood is redistributed to the brain ('brain-sparing'). Sequential changes of the cerebral and placental circulation in parallel in comparisons between basal conditions and acute hypoxic stress have not yet been thoroughly studied in human fetuses.. To explore acute fetal middle cerebral artery (MCA) circulatory changes relative to umbilical artery (UA) blood flow in a clinical experimental model with hypoxic stress provoked by uterine contractions during an oxytocin challenge test (OCT).. Prospective comparative between imminently compromised (OCT positive) and un-compromised (OCT negative) fetuses.. 82 term pregnancies suspected of intrauterine growth restriction were exposed to simultaneous electronic fetal heart rate monitoring and Doppler recordings of pulsatility index (PI) in the UA and MCA during basal conditions and during uterine contractions and relaxations at an OCT.. Sequential changes of UA and MCA PI, OCT positive vs. negative cases. Nonparametric statistics with a P < 0.05 considered significant.. The UA PI was significantly higher in OCT positive cases (N = 10) compared with OCT negative cases (N = 72) during uterine contractions and relaxations, but not during basal measurements. During contractions and relaxations the MCA PI decreased significantly in both groups (brain-sparing), but significantly more in OCT positive cases.. During acute hypoxic stress, changes towards a centralization of blood flow to the brain develop in imminently compromised (OCT positive) fetuses at an expense of the umbilicoplacental blood flow, and the brain-sparing flow is more pronounced than in un-compromised (OCT negative) fetuses.

Topics: Birth Weight; Female; Fetal Hypoxia; Humans; Middle Cerebral Artery; Oxytocin; Placental Circulation; Pregnancy; Prospective Studies; Ultrasonography, Doppler; Ultrasonography, Prenatal; Umbilical Arteries; Uterine Contraction

We report a signaling mechanism in rats between mother and fetus aimed at preparing fetal neurons for delivery. In immature neurons, gamma-aminobutyric acid (GABA) is the primary excitatory neurotransmitter. We found that, shortly before delivery, there is a transient reduction in the intracellular chloride concentration and an excitatory-to-inhibitory switch of GABA actions. These events were triggered by oxytocin, an essential maternal hormone for labor. In vivo administration of an oxytocin receptor antagonist before delivery prevented the switch of GABA actions in fetal neurons and aggravated the severity of anoxic episodes. Thus, maternal oxytocin inhibits fetal neurons and increases their resistance to insults during delivery.

Topics: Action Potentials; Animals; Animals, Newborn; Benzamides; Chlorides; Female; Fetal Hypoxia; Fetus; GABA-A Receptor Agonists; GABA-A Receptor Antagonists; gamma-Aminobutyric Acid; Hippocampus; In Vitro Techniques; Indoles; Maternal-Fetal Exchange; Neural Inhibition; Neurons; Oxytocin; Parturition; Patch-Clamp Techniques; Pregnancy; Rats; Rats, Wistar; Receptors, GABA-A; Receptors, Oxytocin; Signal Transduction; Sodium Potassium Chloride Symporter Inhibitors; Sodium-Potassium-Chloride Symporters; Solute Carrier Family 12, Member 2; Vasotocin

Oxytocin is used to induce and control parturition, nevertheless, the increase of uterine contractions decreases blood flow and gaseous exchange through the womb predisposing to intra-partum mortality. The objective of the present study was to evaluate the effect of oxytocin on myometrial activity, fetal intrauterine hypoxia and postnatal asphyxia in sows during farrowing. Hybrid (n = 120) sows approaching the time of farrowing were randomly assigned in two groups of 60 animals each. Group I (G(1): control) was treated IM with saline solution and Group II (G(2)) was injected IM with oxytocin (1IU/6kg LW) as a single dose at birth of the first piglet. Both average number of myometrial contractions and intensity in G(2) were greater (P < 0.01) as compared with G(1). The mean of intra-partum stillbirths (IPS's) and those where fetal cardiac frequency (FCF) or heart beats, could not be detected after birth, were greater (P < 0.01) in G(2) as compared with G(1). The average decelerations of FCF known as dips II, which indicate severe hypoxia, was greater in G(2) (P < 0.01) as compared with that of G(1). There was a greater (P < 0.01) number of intra-partum stillbirths, stained with severe meconium in G(2) when compared with G(1). Oxytocin treatment increased (P < 0.01) the number of pigs born alive with ruptured umbilical cords and those with different grades of meconium staining on their skin. It was concluded that administration of oxytocin at the onset of parturition increased the myometrial activity, decreased fetal cardiac frequency, predisposed the rupture of umbilical cords and the degree of meconium staining, and increased intra-partum mortality.

Topics: Animals; Animals, Newborn; Female; Fetal Hypoxia; Fetal Monitoring; Heart Rate, Fetal; Meconium; Myometrium; Oxytocin; Parturition; Pregnancy; Pregnancy Outcome; Random Allocation; Swine; Uterine Contraction

The particulars of 78 patients with fetal demise of the last 14 years were evaluated retrospectively. The most important reason of fetal death was hypoxaemia or anoxaemia. 31 patients were delivered by cesarean section or had spontaneous uterine contractions. Induction of 47 abortions were started with oxytocin or prostaglandins. Within 12 hours 54% of the oxytocin and 67% of the prostaglandin group succeeded in spontaneous delivery. In both groups there were 5 management failure of therapy, so that alternative medication or a cesarean section lead to delivery.

Topics: Cesarean Section; Delivery, Obstetric; Female; Fetal Death; Fetal Hypoxia; Humans; Labor, Induced; Oxytocin; Parity; Pregnancy; Prostaglandins

A total of 65 women in labor complicated with uterine inertia were investigated for tissue pO2 and cardiac performance of fetuses under the effect of oxytocin. The authors stated that the aggravation of fetal status in drug-induced labors resulted from poorer tissue oxygenation caused by the activation of uterine contractility. In this line, hypoxic changes of the fetus were more pronounced in pregnancies complicated by nephropathy or prolonged pregnancy. Accurate monitoring of the fetal status and the character of induced labor course was found to be mandatory. Before oxytocin induction the fetus should be protected with diazepam.

Topics: Adult; Female; Fetal Heart; Fetal Hypoxia; Fetal Monitoring; Fetus; Humans; Labor, Induced; Oxygen Consumption; Oxytocin; Pregnancy

Four cases are presented in which increased QRS complex voltages or deviation of the mean electrical axis were observed in the fetus by direct fetal electrocardiogram (ECG) during delivery under anaesthesia. There was transformation of the initial QRS aspect before delivery. These changes were only observed when large doses of oxytocin (20 IU in 500 ml) were used after Pentothal administration in deliveries in which other fetal ECG alterations (bradycardia, ST changes, T inversion) and/or low pH values had been observed. In case 1 there were ST level changes, inversion of the T wave and transformation of the QRS complex from RS to Rs. Case 2 showed a change from RS to QR type complex associated with repolarization defects. In cases 3 and 4, ST level changes, inversion and increased QRS complex voltages were observed. We checked that the modifications observed were not due to changes in position of the fetus during recording. It is thought that the acute redistribution of the fetal blood volume due to oxytocin overstimulation in fetal hearts with hypoxic signs may lead to compensatory mechanisms such as tachycardia, increased contractile activity (higher QRS) and functional predominance of one side of the fetal heart (deviation of the electrical axis) subjected to sudden load.

Topics: Adult; Electrocardiography; Female; Fetal Hypoxia; Fetal Monitoring; Heart Rate, Fetal; Humans; Labor, Obstetric; Oxytocin; Pregnancy

Topics: Administration, Intranasal; Adult; Cardiotocography; Cesarean Section; Female; Fetal Distress; Fetal Hypoxia; Heart Rate, Fetal; Humans; Infant, Newborn; Oxytocin; Pregnancy; Risk Factors; Uterine Contraction

The effect of hypoxemia on arginine vasopressin (AVP) and oxytocin (OT) release was investigated in the chronically catheterized fetus and ewe. During 30 min of 10% maternal oxygen delivery, mean (+/- SEM) arterial PO2 decreased from 105 +/- 10.6 to 48 +/- 3.5 mm Hg in the ewe and from 21 +/- 1.3 to 12 +/- 0.8 mm Hg in the fetus (each P less than 0.001). Arterial PCO2 decreased from 35 +/- 4.4 to 29 +/- 1.0 mm Hg in the ewe, whereas fetal PCO2 decreased from 43 +/- 2.3 to 35 +/- 3.5 mm Hg (P less than 0.05). Blood pH increased from 7.44 +/- 0.03 to 7.56 +/- 0.04 in the ewe (P less than 0.01) and from 7.36 +/- 0.004 to 7.40 +/- 0.006 in the fetuses (P less than 0.01). Baseline mean AVP levels were identical in ewes and fetuses (0.7 +/- 0.1 microU/ml). After 30 min of hypoxia, plasma AVP levels remained unchanged in the ewes (0.9 +/- 0.1), but increased dramatically in the fetuses (47 +/- 21 microU/ml) (P less than 0.001). There was a highly significant correlation between the duration of hypoxia and log fetal AVP concentrations (r = 0.85). The log fetal plasma AVP also was inversely correlated to the log fetal PO2 values (r = 0.83). Mean baseline fetal and maternal plasma OT levels were 2.6 +/- 0.5 microU/ml and 2.2 +/- 0.5 microU/ml, respectively. After 30 min of hypoxia fetal and maternal OT values were 2.9 +/- 0.8 microU/ml (not significant).

Topics: Animals; Arginine Vasopressin; Carbon Dioxide; Female; Fetal Hypoxia; Hydrogen-Ion Concentration; Hypercapnia; Hypoxia; Maternal-Fetal Exchange; Oxygen; Oxytocin; Pituitary Gland, Posterior; Pregnancy; Pregnancy Complications; Sheep

Topics: Cervix Uteri; Dinoprostone; Female; Fetal Growth Retardation; Fetal Hypoxia; Fetal Monitoring; Humans; Infant, Newborn; Labor, Induced; Oxytocin; Pregnancy; Prostaglandins E; Risk; Uterine Contraction

Topics: Bilirubin; Female; Fetal Blood; Fetal Hypoxia; Humans; Infant, Newborn; Jaundice, Neonatal; Labor, Induced; Oxytocin; Pregnancy; Risk

Topics: Female; Fetal Hypoxia; Fetal Monitoring; Humans; Oxytocin; Placenta Diseases; Placental Insufficiency; Pregnancy; Pregnancy, Prolonged; Uterine Contraction; Uterine Inertia

Epidural block for vaginal delivery was given to 242 women during a 6-month period. Of these, 178 with a spontaneous start of labour and vaginal delivery were studied with respect to the effect of epidural block with bupivacaine-adrenaline on the course of labour and the condition of the infant in women with normal uterine activity and women with primary uterine inertia treated with oxytocin infusion. On average, the 178 women had already had a longer course of labour before the block was applied than women in control groups. The block per se had only a slight effect on the first stage of labour, but the effect on the second stage was more obvious, leading to outlet extraction in 50% of the primiparous women, compared to 12% of the controls. Transitory asphyxia at birth was observed in 4.5% of the infants of mothers with epidural block, but after 5 min, only 1% had an Apgar score of less than 7. Infants of mothers with epidural block were more often placed under observation or treated in the neonatal ward than infants in control groups.

Topics: Anesthesia, Epidural; Anesthesia, Obstetrical; Apgar Score; Asphyxia Neonatorum; Bupivacaine; Epinephrine; Female; Fetal Hypoxia; Humans; Infant, Newborn; Labor, Induced; Labor, Obstetric; Oxytocin; Parity; Pregnancy; Retrospective Studies

A prospective study of primiparous English women and their newborns failed to replicate previous findings that greater irritability was related to higher maternal blood pressure during pregnancy and labour. This apparent lack of replication prompted a search for fetal variables capable of mediating the blood pressure--irritability relationships. Relative fetal growth retardation was found in newborns of women whose peak antenatal blood pressure occurred from 20 to 32 wk gestation. Prenatal growth retardation and exposure to either oxytocin-stimulated labour or higher maternal blood pressure during spontaneous labour were associated with lower intrapartum fetal heart rate. Lower heart rate, in turn, was associated with greater crying and more frequent changes of state during behavioural assessments on the first and fifth days. It is suggested that intrapartum hypoxia is an immediate antecedent of newborn irritability. The blood pressure--irritability relationships may therefore reflect the influence of growth retardation, attributable to increased pregnancy blood pressure, and higher labour blood pressure, respectively, on the ability of the fetus to withstand hypoxia and the degree of hypoxia encountered during labour.

Topics: Anesthesia, Obstetrical; Behavior; Crying; Female; Fetal Hypoxia; Fetus; Heart Rate; Humans; Hypertension; Infant, Newborn; Infant, Small for Gestational Age; Meperidine; Obstetric Labor Complications; Oxytocin; Pregnancy; Pregnancy Complications, Cardiovascular; Prospective Studies

Topics: Dystocia; Female; Fetal Hypoxia; Humans; Oxytocin; Pregnancy; Uterine Contraction

Topics: Acute Disease; Chronic Disease; Estriol; Female; Fetal Distress; Fetal Heart; Fetal Hypoxia; Heart Rate; Humans; Maternal-Fetal Exchange; Oxygen Consumption; Oxytocin; Placenta Diseases; Pregnancy; Prenatal Diagnosis; Ultrasonography; Umbilical Cord