Oxytocin Challenge Test Research Articles

Assessment of maternal and fetal outcomes according to induction methods following negative oxytocin challenge test

Background/Aim: There is insufficient information about how long fetal well-being will last after a negative oxytocin challenge test (OCT) and the factors affecting this process. We aim to evaluate maternal and perinatal outcomes in high-risk patients who had negative OCTs and to investigate the effects of methods of induction on the development of fetal distress. Methods: The study was designed as a retrospective cohort study. Data of patients who were hospitalized in the perinatal intensive care unit due to high-risk pregnancies between January 2016 and December 2016 were reviewed retrospectively. The patient’s gestational age, gravidity, parity, and body mass index (BMI), risk factors leading to the OCT, labor induction methods used following a negative OCT, time from negative OCT to delivery, mode of delivery, and indications for cesarean section were recorded. In addition, data regarding fetal sex, birth weight, birth height, labor complications, Apgar scores at minutes 1 and 5, admission to the neonatal intensive care unit (NICU), indications for NICU admission, length of NICU stay, and stillbirth were also recorded. Results: OCT was performed on 551 patients and was negative in 447 patients. Among patients with a negative OCT, labor induction was preferred in 427 (95.5%) patients. When fetal distress development was assessed according to the induction method used following a negative OCT, fetal distress developed in 9.1% of 427 patients who underwent labor induction. Conclusion: When outcomes were considered in pregnant women with a negative OCT, it was observed that there were no fetal deaths and a limited number of newborns with low Apgar scores. Further randomized studies are needed to draw definitive conclusions.

Preeclampsia: Recent Advances in Predicting, Preventing, and Managing the Maternal and Fetal Life-Threatening Condition.

Preeclampsia accounts for one of the most common documented gestational complications, with a prevalence of approximately 2 to 15% of all pregnancies. Defined as gestational hypertension after 20 weeks of pregnancy and coexisting proteinuria or generalized edema, and certain forms of organ damage, it is life-threatening for both the mother and the fetus, in terms of increasing the rate of mortality and morbidity. Preeclamptic pregnancies are strongly associated with significantly higher medical costs. The maternal costs are related to the extra utility of the healthcare system, more resources used during hospitalization, and likely more surgical spending due to an elevated rate of cesarean deliveries. The infant costs also contribute to a large percentage of the expenses as the babies are prone to preterm deliveries and relevant or causative adverse events. Preeclampsia imposes a considerable financial burden on our societies. It is important for healthcare providers and policy-makers to recognize this phenomenon and allocate enough economic budgets and medical and social resources accordingly. The true cellular and molecular mechanisms underlying preeclampsia remain largely unexplained, which is assumed to be a two-stage process of impaired uteroplacental perfusion with or without prior defective trophoblast invasion (stage 1), followed by general endothelial dysfunction and vascular inflammation that lead to systemic organ damages (stage 2). Risk factors for preeclampsia including race, advanced maternal age, obesity, nulliparity, multi-fetal pregnancy, and co-existing medical disorders, can serve as warnings or markers that call for enhanced surveillance of maternal and fetal well-being. Doppler ultrasonography and biomarkers including the mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), and serum pregnancy-associated plasma protein A (PAPP-A) can be used for the prediction of preeclampsia. For women perceived as high-risk individuals for developing preeclampsia, the administration of low-dose aspirin on a daily basis since early pregnancy has proven to be the most effective way to prevent preeclampsia. For preeclamptic females, relevant information, counseling, and suggestions should be provided to facilitate timely intervention or specialty referral. In pregnancies complicated with preeclampsia, closer monitoring and antepartum surveillance including the Doppler ultrasound blood flow study, biophysical profile, non-stress test, and oxytocin challenge test can be arranged. If the results are unfavorable, early intervention and aggressive therapy should be considered. Affected females should have access to higher levels of obstetric units and neonatal institutes. Before, during, and after delivery, monitoring and preparation should be intensified for affected gravidas to avoid serious complications of preeclampsia. In severe cases, delivery of the fetus and the placenta is the ultimate solution to treat preeclampsia. The current review is a summary of recent advances regarding the knowledge of preeclampsia. However, the detailed etiology, pathophysiology, and effect of preeclampsia seem complicated, and further research to address the primary etiology and pathophysiology underlying the clinical manifestations and outcomes is warranted.

The Oxytocin Challenge Test: Is it Useful in the Management of Oligohydramnios?

An oxytocin challenge test (OCT) is a tool used to evaluate placental insufficiency, but it can also be time- and labor-intensive. Studies suggest that OCT may allow for early intervention before fetal acidemia in cases of fetal growth restriction (FGR), but its use for other indications is not well-defined. The objective of the study was to determine whether the use of an OCT prior to induction for oligohydramnios reduces the risk of cesarean delivery for nonreassuring fetal heart tracing.

Improving Neonatal and Maternal Outcome by Inducing Mild Labor before Elective Cesarean Section: The Lacarus Randomized Controlled Trial

Background: Newborns delivered by elective cesarean section (CS) are at higher respiratory risk than those delivered vaginally or by CS proceeded by labor (secondary CS). The oxytocin challenge test (OCT) induces uterine contractions that trigger the release of fetal hormones regulating lung fluid clearance during transition from the uterine to an air-breathing environment. Objectives: The aim is to summarize current evidence and outline the Lacarus trial protocol. Methods: Literature review informed the design of a randomized placebo-controlled multicenter trial of OCT preceding elective CS in 1,450 women with a singleton pregnancy due for CS at >35 weeks gestation, without preceding contractions, rupture of the membranes, or antenatal steroids. OCT comprises the infusion of oxytocin 5 IU/500 mL Ringer lactate at a rate of 12 mL/h, doubling every 10 min until inducing 5 uterine contractions per 15-min interval. The primary endpoint is the occurrence of neonatal respiratory morbidity within 24 h after birth. Secondary endpoints include biochemical and physiological parameters of fetal and maternal well-being, such as breastfeeding rate and fetal plasma copeptin concentrations. Conclusion: This is the first trial to test the hypothesis that oxytocin-induced contractions before elective CS is a promising application of physiologic principles gleaned from natural birth to improve neonatal and maternal outcomes.

The Present Utility of the Oxytocin Challenge Test-A Single-Center Study.

Introduction: The oxytocin challenge test (OCT) used to be one of the most important tools in assessing fetal well-being before ultrasonography became prevalent. We show that, after modifying the classification of the results and the intervention algorithm, OCT can still be a useful tool in present-day obstetrics. Material and methods: The study included 318 OCTs performed in patients admitted to our department from 2010 to 2012. A modified classification of test results was introduced, dividing the results in four groups: I-negative, II-positive, III-non-diagnostic and type IV (fetal tachycardia or increased variability). The purpose of the study was to evaluate the clinical significance of OCT in assessing intrauterinal fetal well-being and predicting the necessity for ending the pregnancy. Results: A significant difference (p < 0.001) in the delivery method and the indications for cesarean sections (CS) was found between negative and positive OCT results. CS indicated by an abnormal fetal heart rate (FHR) pattern had to be performed in 40% of cases with positive OCT results, having constituted 84.6% of all CSs in this group. After negative OCTs, 12.8% pregnancies were ended by CS from FHR indications (62.3% of all the indications). Conclusions: A positive OCT result can be a valuable predictor of an abnormal fetal heart rate pattern after the test and during the delivery, as well as a higher probability of a CS from cardiotocography (CTG) indications, with positive predictive value (PPV) 0.50 and negative predictive value (NPV) 0.85.

Different prostaglandin F2 α secretion in response to oxytocin injection between pregnant and non-pregnant cows: effect of the day of oxytocin challenge test for determining the difference.

The present study was conducted to determine the difference in plasma prostaglandin F2 α metabolite concentrations following oxytocin (OT) challenge between pregnant and non-pregnant cows. Experiment 1: cows were subjected to the OT challenge test on days 12, 14 or 16 (day of estrus=day 0) with or without prior insemination and plasma 13,14-dihydro-15-keto prostaglandin F2 α (PGFM) concentrations were measured from -30 to 180min after OT injection. On day 16, the increment of plasma PGFM concentrations in response to OT injection was significantly smaller in pregnant than that in cyclic cows. On days 12 and 14, there was little OT-induced PGFM secretion and no difference in PGFM increase between the pregnant and cyclic cows. Experiment 2: cows were inseminated on day 0 and subjected to the OT challenge test on day 16. Cows were classified into non-pregnant/early embryonic death (NP/EED), late embryonic death (LED) and pregnant (PREG) groups. The increment of PGFM concentrations in response to OT injection was less in both PREG and LED groups than that in the NP/EED group. In conclusion, plasma PGFM secretion induced by OT is suggested as the base of pregnancy diagnosis prior to returning estrus in cows.

Fetal Release of Copeptin in Response to Maternal Oxytocin Administration: A Randomized Controlled Trial.

To test whether an oxytocin challenge test raises neonatal levels of copeptin, the C-terminal portion of proarginine vasopressin, a sensitive stress marker elevated in neonates born by vaginal delivery as opposed to elective cesarean delivery. In a randomized controlled trial in women with a singleton pregnancy undergoing elective cesarean delivery at greater than 36 weeks of gestation and no contractions or rupture of membranes, we compared arterial umbilical cord plasma concentrations of copeptin between neonates exposed to an oxytocin challenge test before elective cesarean delivery and those administered saline infusion (placebo group). Women randomized to an oxytocin challenge test received 5 international units/500 mL oxytocin Ringer lactate infused at a rate of 12 mL/h and doubled every 10 minutes until it induced three uterine contractions per 10-minute interval, at which point it was discontinued. Neonatal copeptin levels were the primary endpoint. Secondary endpoints included biochemical and physiologic parameters of fetal and maternal well-being. From January 2012 to October 2012 and from September 2013 to January 2015, 78 women underwent an oxytocin challenge test and 78 placebo infusion, of whom 12 and 11, respectively, were excluded as a result of insufficient blood sample volume for analysis. Umbilical cord plasma copeptin levels [median (range)] were higher in neonates who underwent an oxytocin challenge test than those who underwent placebo infusion: 22.2 (3.22-2,319) compared with 7.39 (2.5-344.6) pmol/L (P<.001). There were no statistically significant differences between the two groups in secondary outcomes. Oxytocin challenge test-induced contractions before elective cesarean delivery trigger fetal copeptin release. ClinicalTrials.gov, https://clinicaltrials.gov, NCT01962701.

Salivary oxytocin concentrations in response to running, sexual self-stimulation, breastfeeding and the TSST: The Regensburg Oxytocin Challenge (ROC) study

Intranasal oxytocin (OXT) application is emerging as a potential treatment for socio-emotional disorders associated with abnormalities in OXT system (re-) activity. The crucial identification of patients with such abnormalities could be streamlined by the assessment of basal and stimulus-induced OXT concentrations in saliva, using a simple, stress-free sampling procedure (i.e. an OXT challenge test). We therefore established the Regensburg Oxytocin Challenge (ROC) test to further validate salivary OXT concentrations as a practical, reliable and sensitive biomarker.OXT concentrations were quantified by radioimmunoassay in samples collected at home by healthy adult male and female volunteers before and after running (“Run”) or sexual self-stimulation (“Sex”). In lactating women, salivary OXT concentrations were quantified before, during and after breastfeeding. Salivary OXT along with salivary cortisol and heart rate were monitored in healthy adult participants undergoing the Trier Social Stress Test (TSST).The home-based “Run” and “Sex” challenges as well as the laboratory-based TSST caused quantifiable, rapid, and consistent increases in salivary OXT (approximately 2.5-fold after 10–15min), which were similar for men and women. Breastfeeding did not result in measurably increased salivary OXT levels, probably because the short pulses of OXT release characteristic for lactation were missed.Taken together, ROC tests reliably assess the responsiveness of the OXT system (i.e., the increase in salivary OXT concentrations as compared to basal levels) to challenges such as “Run“ and “Sex“ at home or psychosocial stress (TSST) in the laboratory. Further studies with larger sample numbers are essentially needed in order to reveal individual differences in ROC test outcomes depending on, for example, genetic or environmental factors.

Effects of exogenous oxytocin on uterine blood flow in puerperal dairy cows: The impact of days after parturition and retained fetal membranes

The objective of this study was to examine whether an oxytocin challenge test (OCT), evaluated by measuring the changes in uterine blood flow using transrectal colour Doppler ultrasonography, is a suitable non-invasive method to determine uterine contractility in puerperal dairy cows. The changes in uterine blood flow during uterine contractions induced by oxytocin were evaluated on days 2 and 5 postpartum (pp). Twelve clinically healthy Holstein cows were randomly assigned into two groups: (1) oxytocin group (n=7), 50 IU oxytocin injected IM and (2) control group (n=5), 5 mL saline injected IM. Blood flow volume (BFV) and pulsatility index (PI) in the uterine arteries were determined before and after injection for 120 min on days 2 and 5 pp. BFV declined and PI increased rapidly after oxytocin injection on day 2 (P<0.05), whereas oxytocin on day 5 pp did not cause changes in blood flow parameters. The result confirmed that uterine responsiveness to oxytocin decreases with time postpartum in healthy cows. The same OCT was applied in cows with retained fetal membranes (n=6) on day 2 pp, however uterine blood flow showed no change after oxytocin injection. The results showed that an OCT on day 2 pp may be a useful method for investigating the uterine contractile response to oxytocin (reflected as the decrease of uterine blood flow) and the potential pathophysiology of uterine involution in cows.

System for objective assessment of fetal activity

Fetal activity is an important indicator of fetal well-being. It is proposed to assess this activity using the pulsed wave Doppler method to collect fetal activity data and dedicated software for on-line processing. The system, addressed to 3rd trimester pregnancies, provides information on presence of pseudobreathing, the heart rate trace, the fetal movement trace, the movement velocity spectrogram, histograms of the velocity and acceleration of both the body movements and pseudobreathing, parameters of these histograms (mean values, standard deviations, shape descriptors), and cumulative counts of the velocity histograms. These parameters form the feature vector of the fetal activity. The system was validated by simultaneous echographic and cardiotocographic recordings and during oxytocin challenge tests. Feature vectors obtained from 1 h recordings in 61 pregnancies were submitted to multivariate analysis of variance. Activity patterns of physiological cases and “borderline pathologies” were discriminated using reduced feature vectors, containing cumulative counts of velocity histograms.

Relations between fetal brain‐sparing circulation, oxytocin challenge test, mode of delivery and fetal outcome in growth‐restricted term fetuses

The study was designed as a prospective non-interventional, observational study to elucidate the potential value of fetal middle cerebral artery Doppler velocimetry to identify brain-sparing flow in a surveillance program for suspected intrauterine growth restriction (IUGR). The study was carried out at Skåne University Hospital, Malmö, Sweden. One hundred and twenty-six single pregnancies suspected of IUGR at ≥36 gestational weeks were assessed. The main outcome measures were positive/negative oxytocin challenge test (OCT) and cesarean/vaginal delivery. The pregnancies were managed with ultrasound fetometry, uterine and umbilical artery Doppler flow velocimetry, nonstress test, and an OCT to decide the optimal time and mode of delivery. Cases with a positive OCT were promptly delivered by cesarean section, whereas negative cases were allowed a trial of labor. Middle cerebral artery Doppler flow velocimetry results were blinded to the managing obstetricians. Brain-sparing flow was defined as a middle cerebral artery-to-umbilical artery pulsatility index ratio of <1.08. Nonparametric statistics with significance set at p < 0.05 were used, and Cohen's kappa coefficient was calculated for congruence of brain-sparing flow with OCT and mode of delivery, respectively. The positive predictive value and sensitivity figures of brain-sparing flow to indicate a positive OCT and cesarean delivery were 33-63%. The inter-rater reliability of brain-sparing flow vs. positive OCT showed a kappa coefficient of 0.19, and brain-sparing flow vs. cesarean section among OCT-negative cases a kappa coefficient of 0.23. Fetal brain-sparing flow is a poor predictor of a positive OCT, and of cesarean section in OCT-negative cases.

Uterine artery flow velocity waveforms during uterine contractions: Differences between oxytocin‐induced contractions and spontaneous labor contractions

To clarify the effects on uterine arterial flow velocity waveforms of uterine contractions following oxytocin infusion and during spontaneous labor. Uterine arterial flow velocity waveforms were obtained by pulsed Doppler methods from 22 women during an oxytocin challenge test (OCT), 26 women during oxytocin-induced labor, and 40 women during spontaneous labor. Mean resistance index (RI) for bilateral arteries was used for analyses. After the onset of labor, flow velocity waveforms were assessed according to cervical dilatation. During OCT, Doppler flow velocimetry was performed when three uterine contractions occurred per 10-min period. RI values did not differ significantly between induced and spontaneous labor during relaxations at any level of cervical dilatation. However, during contractions, RI was significantly higher for induced labor than for spontaneous labor. Absence or reversal of flow was more frequent in the OCT group than in the induced labor group (P < 0.0001). However, no significant differences were found between spontaneous and induced labor groups. Interactions between the contracting uterine body and the relaxing lower segment in oxytocin-induced labor might be associated with differences in uterine arterial flow during contraction between oxytocin-induced and spontaneous labor. However, changes in the intensity of uterine contractions during labor progression might differ between oxytocin-induced and spontaneous labor.

Umbilical cord strangulation by an amniotic band resulting in a stillbirth

Amniotic band syndrome with umbilical cord strangulation is extremely rare and is usually described during second trimester. We present a case of umbilical cord strangulation causing fetal demise in a full-term otherwise healthy fetus. A 39-year-old gravida 15 para 12 after one previous cesarean section presented with reduced fetal movements at the 41st gestational week. On admission, fetal heart tracing, biophysical profile and oxytocin challenge test were normal. Later, an intrauterine fetal demise was diagnosed. After delivery, an amniotic band causing strangulation of the umbilical cord was observed. The fetus was without apparent anomalies. Although extremely rare, constriction of the umbilical cord by an amniotic band can cause its strangulation followed by a stillbirth even in full-term otherwise healthy fetus.

Fetal ductus venosus, middle cerebral artery and umbilical artery flow responses to uterine contractions in growth‐restricted human pregnancies

To explore fetal ductus venosus (DV) flow velocity changes relative to umbilical artery (UA) blood flow and brain-sparing flow (BSF) during uterine contractions. Forty-five term fetuses suspected of having growth restriction were exposed to an oxytocin challenge test (OCT) with simultaneous Doppler velocimetry in the UA, middle cerebral artery (MCA) and DV. Basal BSF was defined as a MCA-to-UA pulsatility index (PI) ratio of < 1.08, and de novo BSF as a decrease in MCA-PI of > or = 1 SD (equivalent to a value of 0.24 units) during the OCT. Basal DV flow velocities were lower in the BSF group (n = 7) than they were in the non-BSF group (n = 38). During the OCT, DV flow velocity parameters changed in neither group but MCA-PI decreased in the non-BSF group. A crude de novo BSF was not associated with DV flow velocity changes, but when UA-PI changes were considered, a serial relationship was found between decreased UA-PI, increased DV flow velocity, and decreased MCA-PI. When UA-PI increased, the MCA-PI still decreased (though not significantly) but DV flow velocity parameters remained unchanged. Established fetal BSF is associated with low DV flow velocities, but in an acute sequence there might be two contrasting courses along which BSF develops: one with an increase and one with a decrease in the UA vascular flow resistance. In the former situation the DV flow velocity increases, while in the latter situation the role of the DV in the acute redistribution of fetal blood flow is unclear.

Intracerebral regional distribution of blood flow in response to uterine contractions in growth-restricted human fetuses

Objective To explore middle cerebral artery (MCA) and anterior cerebral artery (ACA) blood flow responses to superimposed acute hypoxemia in growth-restricted fetuses with and without established brain-sparing flow during basal conditions. Material and methods 47 term fetuses suspected of growth restriction were exposed to an oxytocin challenge test with simultaneous cardiotocography and Doppler velocimetry in the umbilical artery, MCA and ACA. The MCA-to-ACA pulsatility index (PI) ratio was calculated during basal conditions, contractions and relaxations. Basal brain-sparing flow was defined as an MCA-to-umbilical artery PI ratio of < 1.08, de novo brain-sparing flow in the MCA as an MCA PI decrease with ≥ 1 standard deviation during uterine contractions or relaxations compared with basal measurements, and de novo brain-sparing flow in the ACA as an ACA PI decrease with ≥ 1 standard deviation. Non-parametric statistical tests were used with P < 0.05 considered significant. Results MCA and ACA PI were both significantly lower in the brain-sparing flow group ( N = 8) during basal conditions ( P ≤ 0.01). During the oxytocin challenge test, MCA and ACA PI both decreased in the non-brain-sparing flow group ( N = 39) ( P ≤ 0.02) but not in the brain-sparing flow group ( P ≥ 0.4). The MCA-to-ACA PI ratio remained unchanged in both groups. de novo brain-sparing flow calculations revealed no preferential flow to any cerebral artery. Conclusion Cerebral circulatory responses to acute hypoxemia are synchronized in the middle and anterior cerebral arteries without any preferential regional flow distribution.

Acute centralization of blood flow in compromised human fetuses evoked by uterine contractions

Background 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. Aim 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). Study design Prospective comparative between imminently compromised (OCT positive) and un-compromised (OCT negative) fetuses. Subjects and methods 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. Outcome measures Sequential changes of UA and MCA PI, OCT positive vs. negative cases. Nonparametric statistics with a P < 0.05 considered significant. Results 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. Conclusions 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.

Restrained cerebral hyperperfusion in response to superimposed acute hypoxemia in growth-restricted human fetuses with established brain-sparing blood flow

Objective To investigate the cerebral circulatory response to superimposed acute hypoxemia in growth-restricted fetuses with established brain-sparing flow (BSF) during basal conditions. Material and methods 76 term fetuses suspected of growth restriction were exposed to Doppler velocimetry in the umbilical artery (UA) and middle cerebral artery (MCA), and in 38–39 cases also in Galen's vein (GV), straight sinus (SS), and transverse sinus (TS), before and during an oxytocin challenge test (OCT), and simultaneous to electronic fetal heart rate monitoring. Nonparametric statistical analyses compared presence/absence of established BSF (MCA-to-UA pulsatility index [PI] ratio < 1.08) with a two-tailed P < 0.05 considered significant. Results The OCT (positive/negative) was not different in the BSF group (BSFG, N = 16) and the normal flow group (NFG, N = 60) ( P = 0.2). During uterine contractions, the MCA PI decreased in the NFG, but not in the BSFG. De novo GV pulsations and increase of GV maximum flow velocity occurred during contractions in the NFG, but not in the BSFG. Significant SS flow velocity waveform changes were found in neither group and TS flow changes in the BSFG only. Conclusions Fetuses without established brain-sparing flow during basal conditions responded with both arterial and venous brain-sparing flow during acute hypoxemia, whereas in fetuses with established brain-sparing flow the cerebral circulatory responses were absent or equivocal. Fetuses with established brain-sparing flow may have a limited capacity of further cerebral hyperperfusion during superimposed acute hypoxic stress.

Acute changes of cerebral venous blood flow in growth-restricted human fetuses in response to uterine contractions.

The fetal cerebral venous circulation during acute hypoxic stress provoked by uterine contractions has not been studied previously. The aim of this study was to explore the cerebral venous circulation during an oxytocin challenge test (OCT) in intrauterine growth-restricted (IUGR) fetuses. Doppler recordings of blood flow in the vein of Galen (GV), straight sinus (SS) and transverse sinus (TS) before and during uterine contractions and relaxation were obtained at the same time as electronic fetal heart rate (FHR) monitoring in 44 term IUGR fetuses. The OCT was classified as negative (normal FHR) or positive (late FHR decelerations). Non-parametric statistics were used to test differences between OCT groups. In OCT-negative cases (n = 39), de novo pulsations occurred in the GV, and SS flow velocities increased during contractions compared with basal measurements. There were no significant differences in TS flow. Flow recordings were less often obtained from OCT-positive cases (n = 5), making comparisons with OCT-negative cases uncertain. In uncompromised IUGR fetuses an acute cerebral venous hyperperfusion develops in response to uterine contractions. Pulsations in the GV are detected but are unlikely to be an ominous sign in this situation. The more centrally located TS was less discriminating for acute cerebral venous blood flow changes.

Clinical significance of uterine artery blood flow velocity waveforms during provoked uterine contractions in high-risk pregnancy.

To determine whether, in a group of high-risk pregnancies undergoing an oxytocin challenge test (OCT), uterine artery Doppler velocimetry will identify fetuses at risk of distress during the provoked contractions. Bilateral uterine artery Doppler velocimetry was performed simultaneously with electronic fetal heart rate (FHR) recordings in 67 high-risk pregnancies subjected to an OCT. Flow velocity waveforms (FVWs) were classified according to pulsatility index (PI), presence of diastolic notching and a novel classification of FVW shapes. The OCT was classified as negative (normal) or positive (late FHR decelerations). Only OCT-negative cases were allowed a trial of vaginal delivery. Non-parametric statistical methods were used to test for differences between the OCT groups. There was no difference in prevalence of high PI or diastolic notching in OCT-positive (n = 10) and OCT-negative (n = 57) cases at basal (resting) measurements or between uterine contractions in either uterine artery (P > or = 0.3). During contractions the PI could not be used for assessment due to the biphasic shape of the FVWs, but there was no difference in distribution of FVW classes between the groups in either the placental side (P > or = 0.3) or contraplacental side (P > or = 0.6) uterine artery. No significant associations between PI or FVW class distribution and birth asphyxia or operative delivery for fetal distress in labor were found (P > or = 0.1). During uterine contractions there is no difference in uterine artery FVW pattern between OCT-positive and OCT-negative cases. Recording of uterine artery FVWs during the OCT seems to be of limited clinical relevance.

Prospect for Vaginal Delivery of Growth-Restricted Fetuses With Abnormal Umbilical Artery Blood Flow

Prompt operative delivery is commonly carried out when intrauterine growth restriction (IUGR) is suspected or there is absent or reversed end-diastolic blood flow velocity in the umbilical artery (UA). When resistance to UA blood flow is only slightly or moderately increased, however, there is no general agreement on when or how to deliver the fetus. The goal in this setting is to avoid exposing the fetus to hypoxia and distress when possible. A trial of vaginal delivery would be permissible only if there is a minimal risk of distress in labor. This prospective study evaluated planned vaginal delivery in 84 women with singleton term pregnancies if IUGR was suspected. UA Doppler velocimetry was carried out, as well as an oxytocin challenge test (OCT). The test was done at or after 36 weeks gestational age and, if it was negative, a trial of vaginal delivery was planned. UA Doppler velocimetry yielded normal findings in 51 cases but abnormal results in 33. In the latter cases, the pulsatility index was increased and forward-diastolic blood flow was maintained. These groups were similar in maternal age, parity, and the delay between the OCT and delivery. Mean gestational age at delivery was significant in the abnormal UA blood flow group. In addition, the OCT was positive more often (33% vs. 16%) in this group, and vaginal delivery was less frequent (40% vs. 63%). After labor had begun, 68% of women with abnormal UA blood flow and 76% of those with normal flow delivered vaginally. The vaginal delivery rate and transfer to the neonatal intensive-care unit did not differ appreciably in the 2 blood flow groups. Three infants with severely restricted growth had malformations, and 1 died as a result. One infant had meconium aspiration and pneumothorax but eventually was discharged home. Vaginal deliveries were significantly less frequent in the presence of abnormal UA Doppler velocimetry in this study, but when a trial of labor was ultimately done, the rates were similar in women with normal and those with abnormal blood flow patterns. There was no indication that any fetus was exposed to harmful hypoxia or distress. The OCT continues to be useful in some cases for assessing the status of growth-restricted fetuses and those with mild to moderate changes in UA blood flow.