Evaluation of fetal heart monitoring in the first stage of labor

OBJECTIVE: To evaluate the usefulness of continuous electronic fetal heart rate (FHR) monitoring in the first stage of labor. METHODS: A total of 814 pregnant women in labor without identifiable risk factors was divided into two groups. In group A (468 cases), continuous FHR monitoring began in the earliest phase of the first stage of labor (cervical dilatation < or = 4 cm), while in group B (346 cases) it began when the cervical dilatation was > 4 cm. Initial FHR tracings were normal in all 814 cases. The fetal monitoring findings were analyzed at 10-min intervals, and comparisons were made between the two groups concerning FHR findings and their correlation with the state of the newborns. RESULTS: No significant difference was found between the two groups in the incidence of repetitive variable decelerations (1.9% and 1.7%, respectively); sporadic variable decelerations (9.2% and 8.7%, respectively); persistent repetitive late decelerations that resulted in Cesarean section (1.1% and 1.4%, respectively); or sporadic late decelerations (8.3% and 8.1%, respectively). One newborn from each group required intensive neonatal care. CONCLUSIONS: The same tracing sufficiency of fetal stress was observed in the two groups. However, the manner of labor supervision in group B seemed to be more beneficial, because of greater maternal comfort, a lower necessity for personnel, lower consumption of cardiotocographic materials and the possibility of labor induction for more women. Since fetal monitoring is widely used, it is preferable to start continuous FHR monitoring when the dilatation of the cervix approximates 4-5 cm (second phase of the first stage of labor) without risk of fetal loss.     

Is intrapartum vibroacoustic stimulation an effective predictor of fetal acidosis?

OBJECTIVE: The hypothesis of this prospective study is that intrapartum vibroacoustic stimulation (VAS) is an effective predictor of fetal acidosis during labor. Various clinical conditions, such as term versus preterm gestation, first stage versus second stage of labor, and fetal heart rate (FHR) variable decelerations versus late decelerations will be tested. METHODS: During the study period, 113 patients were studied prospectively in either active phase of first stage (n = 53) or during the second stage of labor (n = 60). They were selected from cases exhibiting moderate to severe FHR variable decelerations or late decelerations. The fetuses of study subjects received a VAS for three seconds and FHR changes were recorded. Fetal scalp blood pH or umbilical arterial blood pH was obtained within 15 minutes of VAS. The relationship between FHR responses to VAS and fetal blood pH in term and preterm gestations, the relationship of two tests (VAS and fetal blood pH) to type of FHR decelerations, and the predictability of neonatal morbidity by two tests were analyzed. Where appropriate, Fisher's exact test (p < 0.05 was considered statistically different) and the odd ratio with 95% confidence intervals were used for statistical analyses. RESULTS: Excellent association between acceleration response to VAS and pH > or = 7.20, and between a negative response to VAS (no acceleration or decelerations) and pH < 7.20 were found in the first stage of labor, the second stage of labor, and the combination of both stages together (p = 0.0001, OR = 10.6 [3.3-34.0]). It was observed that negative VAS responses for predicting fetal acidosis (pH < 7.20) were comparable between term (> or = 37 weeks) and preterm (< 37 weeks, > or = 34 weeks) fetuses. Since the preterm fetuses enrolled in the study were limited in number, it is difficult to draw adequate conclusions. The positive predictive value (PPV) of fetal acidosis was 67% in both groups of FHR variable decelerations and late decelerations, but the false negative rate of acceleration VAS response for predicting no acidosis was significantly higher in the group of late decelerations (29% vs 8%, p = 0.034). Finally, both a negative VAS response and fetal acidosis (pH < 7.20) have equal predictability for neonatal morbidity. The PPV of NICU admission by a negative VAS response was two times higher than that of fetal acidosis (PPV = 61% vs 29%, p = 0.038). CONCLUSION: We found that intrapartum VAS was an effective predictor of fetal acidosis in cases of FHR variable decelerations, but its predictability for fetal acidosis in cases of FHR late decelerations was limited. Both VAS and fetal blood pH are good predictors of neonatal morbidity.     

脐血乳酸水平及胎心监护图形预测胎儿窘迫的价值

目的　探讨新生儿脐动脉血乳酸水平及胎心监护图形预测胎儿窘迫的价值。方法　测定 73例胎心监护图形为不良图形 (胎心基线异常、重度变异减速、轻度变异减速、心动过速 )的新生儿(病例组 )和 118例产前无胎儿窘迫征象 ,出生后 1分钟Apgar评分≥ 9分的新生儿 (对照组 )出生后脐动脉血乳酸水平。结果　病例组中产钳助产率明显高于对照组 (P <0 0 1) ,顺产率低于对照组 (P<0 0 1)。病例组中 ,胎心重度变异减速多发于第二产程 ;胎心基线异常的新生儿Apgar评分≤ 7分的发生率高于重度变异减速、轻度变异减速、心动过速的新生儿 (P <0 0 5 )。病例组中 ,胎心基线异常者脐动脉血乳酸水平为 (4 5 5± 0 2 3 )mmol/L ;重度变异减速者为 (3 84± 0 40 )mmol/L ,出现以上两种图形的新生儿脐动脉血乳酸水平均明显高于对照组 (P <0 0 1)。轻度变异减速者脐动脉血乳酸水平为 (2 63± 0 3 2 )mmol/L ;心动过速者脐动脉血乳酸水平为 (2 5 5± 0 46)mmol/L。并且轻度变异减速与心动过速者脐动脉血乳酸水平与对照组比较 ,差异无显著性 (P >0 0 5 )。结论　测定新生儿脐动脉血乳酸水平是一种有效、准确的诊断胎儿窘迫的方法。胎心基线异常、重度变异减速与胎儿窘迫的发生密切相关 ;轻度变异减速、心动过速与胎     

Sporadic fetal heart rate decelerations associated with electrocortical changes in fetal lambs

AIM: The purpose of this study was to determine a relationship between sporadic fetal heart rate (FHR) decelerations and fetal electrocortical changes in physiologically normal sheep fetuses. MATERIALS AND METHODS: A total of 20 experimental observations were conducted on eight chronically instrumented fetal lambs. For electrocorticogram (ECoG) recording, two stainless steel electrodes were implanted bilaterally on the fetal parietal skull. Classifications of ECoG tracings were visually divided into periods of low, high, intermediate and transitional voltage. During day and night observations, sporadic FHR decelerations related to fetal ECoG changes were counted. RESULTS: We found that 65% of the total sporadic FHR decelerations occurred in relation to fetal ECoG changes. The largest number of sporadic FHR decelerations was associated with a switch from low voltage to high voltage ECoG (37%). However, the greatest frequency of sporadic FHR decelerations occurred during intermediate ECoG periods (34%). CONCLUSION: The majority of sporadic FHR decelerations observed in physiologically normal sheep fetuses were associated with fetal ECoG changes.     

第一产程异常胎心监护图形与新生儿结局的关系

目的　探讨第一产程异常胎心监护图形与新生儿结局的关系。方法　回顾分析 2 0 0 2年 8月至 2 0 0 3年 6月在我院足月单胎头位分娩产妇 ,第一产程中胎心率 (FHR)异常图形 2 1 7例 (观察组 )和FHR正常图形的2 6 9例 (对照组 )的临床资料。结果　第一产程异常FHR图形的发生率为 4 4 7% ,常见类型为轻度变异减速(6 4 5 % )、基线变异减弱 (2 1 6 % )和轻度心动过速 (1 2 0 % )。晚期减速、基线变异减弱和重度变异减速是导致新生儿窒息的危险因素。观察组羊水过少 (5 1 % )、脐带缠绕 (2 2 6 % )、羊水粪染 (1 0 6 % )、新生儿窒息 (6 5 % )、新生儿转入NICU(1 0 1 % )的发生率和剖宫产率 (31 8% )明显高于对照组 (P <0 0 5 )。结论　第一产程异常FHR图形的发生率较高 ,其中晚期减速、基线变异减弱、重度变异减速与新生儿窒息的发生相关 ,其他图形可在严密监护下继续试产     

Analysis of umbilical artery flow parameters during fetal variable decelerations using computerized Doppler waveforms

Umbilical artery velocity waves were obtained by Doppler ultrasonography before, during, and after 20 episodes of fetal heart rate (FHR) variable decelerations (VD) during the active stage of labor in 8 women. During 50% of the VD periods, the umbilical artery resistance flow parameters increased significantly (p < 0.01). The increase in resistance preceded the decrease in FHR in six episodes (30%) of VD (AR-VD group; arterial resistance VD) and did not precede the change in FHR in another ten episodes (50%) of VD (VR-VD group; venous resistance VD). In the AR-VD group the FHR accelerations occurred before the decelerations in only 1 case (17%), while in the VR-VD group FHR accelerations preceded the decelerations in 8 out of the 10 episodes (80%). Using these Doppler studies, it may be possible to differentiate between two groups of VD: AR-VD - which are caused by umbilical artery occlusion and thus preceded by a measurable increase in umbilical artery resistance - and VR-VD - which are not preceded by a measurable increase in umbilical artery resistance and may be caused by fetal hypoxia.     

Fetal heart rate monitoring category 3 during the 2nd stage of labor is an independent predictor of fetal acidosis

Objective: To determine whether fetal heart rate (FHR) monitoring categories during the 1st and 2nd stage of labor can predict arterial cord pH?<7.2.

Materials and methods: A case control study was conducted including 653 consecutive term deliveries (37 weeks gestation and above) that were divided according to fetal pH?≤?7.2 (n?=?315) and fetal pH?>?7.2 (n?=?338). Deliveries occurred during the year 2013 in tertiary medical center, where arterial cord pH is routinely taken after birth. Intrapartum FHR monitoring categorization was defined according to the ACOG committee guidelines by two obstetricians. Multivariable models were constructed to control for confounders.

Results: Variable decelerations, late decelerations and bradycardia during the 1st and 2nd stages of labor were significantly higher in group of deliveries ended in cord pH??7.2. A significant association was observed between category 2 and 3 during the 1st stage of labor and pH?≤?7.2. However, while controlling for FHR category 3 at the 2nd stage of labor, 1st stage categorization lost its association with pH?<7.2, and only category 3 during the 2nd stage were noted as an independent risk factor for acidosis.

Conclusion: FHR monitoring category 3 during the 2nd stage of labor is an independent predictor of fetal acidosis as expressed by arterial cord pH?相似文献   

Fetal pulse oximetry: correlation with intrapartum fetal heart rate patterns and neonatal outcome

AIM: To determine how fetal pulse oximetry behaves in various cardiotocographic (CTG) tracings and correlates with neonatal outcome. PATIENTS AND METHODS: Pregnant women undergoing active labor with singleton pregnancies of 32-42 weeks were enrolled. CTG recordings were reassuring or nonreassuring (namely variable or persisting late decelerations). Pulse oximetry values during labor and changing throughout deceleration and recovery phases, duration and frequency of pulse oximetry recordings <30%, and neonatal outcome were determined. One-way anova, Tukey test, chi(2)-test and multiple logistic regression model were used for statistical analysis where appropriate. RESULTS: A total of 156 pregnant subjects were divided into three groups: reassuring fetal heart rate (FHR) patterns (group 1, n=78 [50%]), late decelerations (group 2, n=16 [10.3%]) and variable decelerations (group 3, n=62 [39.7%]). The initial and final pulse oximetry readings, pulse values in first stage of labor, the duration and the frequency of pulse oximetry recordings <30% were significantly different between groups (P<0.001, P<0.001, P<0.001, P=0.001, P<0.001). Fetal acidosis was significantly more frequent with late decelerations (23.1%, P=0.004). A multiple logistic regression model demonstrated that the initial pulse oximetry value during active labor was the most predictive variable of neonatal well-being (P<0.001). CONCLUSION: Decreased fetal pulse oximetry values, especially prolonged and recurrent recordings <30% are well-correlated with abnormal FHR patterns, indicating an association with fetal compromise and metabolic acidosis. Going through active labor with a lower initial value of FSpO(2) more frequently leads to an altered FHR pattern and subsequent adverse fetal outcome.     

Clinical significance of fetal heart rate patterns during labor. II. Late decelerations.

Among a population of high-risk patients in labor who had continuous "direct" electronic monitoring, 147 presented late decelerations and 598 had no decelerations at the time the first stage was completed, or a cesarean section decided upon. A variety of clinical aspects of mother and fetus were analyzed, considering some alterations observed in the FHR pattern. Apgar scores were lower among decelerations, and there was a negative correlation between these two. Maternal pathology, other than PRM, was higher among decelerations and these required enhancement more often. There was very high association with tachycardia, saltatory, and fixed baseline among decelerations, and these infants were very often distressed and born depressed. Within the group of decelerations, small fetuses had lower Apgar scores. There was a negative correlation between number of decelerations and Apgar score. The small fetuses had a high incidence of tachycardia and fixed baseline, saltatory being almost absent. Their neonatal outcome was poor. A comparison of fetal response to distress was done considering age of gestation (premature, term, and postmature) and found to be different. The mechanisms involved in late deceleration are discussed, reviewing the published experimental work. When interpreting FHR patterns, age of gestation should be one of the most important considerations.     

Acute fetal distress

Three different clinical patterns of acute fetal distress may be observed during labor: an ante-partum hypoxia with a persistent nonreactive and "fixed" fetal heart rate (FHR) on admission to the hospital, a progressive intra-partum asphyxia manifested, as the labor continues, by a substantial rise in baseline heart rate, a loss of variability and repetitive severe variable or late decelerations, and finally, as a result of a catastrophic event, a sudden prolonged FHR deceleration to approximately 60 beats per minute lasting until delivery. However the majority of fetuses with nonreassuring tracings of FHR are neurologically intact, as evidenced by the high false-positive rate of electronic fetal monitoring (EFM). Therefore the diagnosis of fetal distress must be corroborated by complementary methods, such as continuous recording of the fetal electrocardiogram or computed-assisted EFM, fetal pulse oximetry or fetal scalp sampling with immediate determination of blood gases or lactates. Defavorable outcome of an acute fetal distress leading to neonatal encephalopathy or death is best predicted by a persisting low Apgar score (<3) for more than 5 minutes and by a severe metabolic acidosis (umbilical artery pH<7,00 and base-excess>-12mmol/l).     

Saline amnioinfusion for relief of repetitive variable decelerations: a prospective randomized study

A prospective randomized study was undertaken in order to further investigate the effect of intrauterine saline amnioinfusion for the relief of repetitive variable decelerations in the first stage of labor. Intrauterine saline amnioinfusion corrects the oligohydramnios that makes the cord more vulnerable to compression during uterine contractions. Included in this study were 96 patients who had repetitive variable decelerations not relieved either by changes in position or by oxygen. Randomization resulted in 49 patients in the infusion group and 47 patients in the noninfusion group. Relief of variable decelerations was 51% in the infusion group, as compared to 4.2% in the noninfusion group. Relief of variable decelerations was more dramatic in the nulliparous infusion group (66.7%) than in the noninfusion group (0%). In the nulliparous patients there was a significant decrease in the rate of cesarean sections for fetal distress, being 14.8% in the infusion group as compared to 47.6% in the noninfusion group. This study clearly showed that saline amnioinfusion is a logical, simple, safe, and effective therapy for the relief of repetitive variable decelerations in the first stage of labor and can lower the incidence of cesarean sections for fetal distress in nulliparous patients. Furthermore, amnioinfusion was much superior to changes in position in treating repetitive variable decelerations.     

第二产程胎心监护异常的处理及临床意义

目的 探讨第二产程胎心监护异常者的分娩方式,及其与产妇并发症和围产儿结局的关系。方法 回顾性分析我院足月单胎头位分娩产妇第二产程中胎心率（FHR）正常的111例（对照组）和胎心率异常的121例（观察组）的资料。结果 FHR异常的发生率为52.2%（121／232）,异常胎心率类型包知中、重度变异减速（VD）81例,占66.9%;晚期减速（LD）27例,占22.3%,其中仅1例发生连续LD;延长减速（PD）4例,占3.3%;VD合并LD2例,占1.7%;VD合并PD3例,占2.5%;基线变异减弱4例,占3.3%。对照组中,阴道助产13例（11.7%）,顺产98例（88.3%）;观察组中,顺产86例（71.1%）,阴道助产35例（28.9%）,其中29例（82.9%）为FHR异常而施术者,两组间比较,差异有显著性（P＜0.05）。观察组、对照组新生儿窒息的发生率（分别为5.0%、1.8%）及产伤的发生率（14.3%、15.4%）比较,差异均无显著性（P＞0.05）;观察组中有1例产妇会阴Ⅲ度撕伤。结论 第二产程中FHR异常的发生率高,多为产程中胎头受压或脐带受压而引起的迷走神经反射或暂时性子宫胎盘血流减少,并非缺氧所致,不必急于干预,以免造成母、儿损伤。     

An active management approach to the postdate fetus with a reactive nonstress test and fetal heart rate decelerations

Reports have shown that a reactive nonstress test (NST) with decelerations in the postdate patient is associated with an increase in perinatal morbidity. Based on these observations, patients who exhibited this fetal heart rate (FHR) pattern during NST had labor induced. The purpose of this report was to determine what impact, if any, this approach had on subsequent maternal and fetal outcome. The pregnancy outcome of 470 patients who delivered during 1984 within seven days of their last NST was compared with data from this institution in 1980. The last NST was reactive in 420 patients (89.4%) and nonreactive in 50 (10.6%). Fetal heart rate decelerations occurred in 130 patients (27.7%); of these, 96 (73.9%) were reactive and 34 (26.1%) nonreactive. Postdate patients whose last NST was reactive with decelerations had similar outcomes to patients with a nonreactive NST on their last test, but less favorable outcomes than patients with reactive tests alone. Comparison with data from our institution in 1980 shows that prompt induction of labor in the postdate patient with a reactive NST and decelerations resulted in significantly lower perinatal morbidity, with no corresponding increase in maternal morbidity. These results lead us to conclude that a reactive NST without FHR decelerations is a reliable indicator of fetal well-being in the postdate pregnancy. However, in the postdate pregnancy with a reactive NST with FHR decelerations, induction of labor is indicated.     

Significance of meconium during labor.

Continuous fetal heart rate (FHR) monitoring and routine fetal scalp blood sampling was utilized in the evaluations of 366 fetuses during labor. One hundred and six patients had meconium in the amniotic fluid at some time during labor. A total of 26,110 uterine contractions were monitored during these 366 labors. The incidence of FHR patterns as a percentage of uterine contractions was calculated for the meconium and nonmeconium groups. Although there was a 3 1/2-fold increase in the incidence of low five-minute Apgar scores (less than 7) in the meconium group, signs of fetal distress were, with rare esception, not significantly different from those in the nonmeconium group. The presence of meconium in the amniotic fluid without signs of fetal asphyxia (late decelerations and acidosis) is not a sign of fetal distress and need not be an indication for active intervention. The combination of fetal asphyxia and meconium staining of the amniotic fluid, however, does enhance the potential for meconium aspiration and a poor neonatal outcome. Universal fetal heart rate monitoring and appropriate fetal acid-base evaluation is recommended for following patients with meconium in the amniotic fluid during labor.     

Severe variable decelerations and fetal pulse oximetry during the second stage of labor

OBJECTIVES: The aim of the study was to investigate the usefulness of fetal pulse oximetry in cases of severe variable decelerations in the second stage of labor. METHODS: It is a prospective study including 58 patients. Thirty-eight patients (group A) had a normal uncomplicated labor and 20 patients (group B) developed severe variable decelerations during the second stage of labor. All patients were primiparous with normal pregnancies and had electronic fetal monitoring of labor in conjunction with fetal pulse oximetry. An estimation of fetal pH and base deficit was performed at delivery in all patients. RESULTS: There was no statistically significant difference in relation to maternal age and gestational age between the two groups. Group A patients did not delivered neonates with metabolic acidosis. Six out of 20 (group B) patients delivered neonates with a pH <7.10 despite a fetal pulse oximetry reading of >30%. CONCLUSIONS: It appears that fetal pulse oximetry is not capable of detecting pre-acidotic or acidotic fetuses during the second stage of labor in patients with severe variable decelerations and the management of such patients should be supported by fetal scalp pH when indicated or otherwise the obstetrician should expedite delivery either with assisted operative delivery or cesarean section. Fetal heart rate monitoring was introduced into clinical practice over 30 years ago. It continues to be the predominant method of intrapartum fetal surveillance despite worries about its accuracy and efficacy.     

Deceleration/contraction ratios as an index of fetal health during labor.

Internal FHR tracings of 259 patients with variable decelerations and 49 with late decelerations were analyzed for frequency and severity of the pattern in an attempt to correlate with fetal pH or Apgar score at 1 minute. A significant increase in the risk of fetal acidosis was associated with a frequency of greater than 30% variable decelerations and 20% late decelerations. It also increased with the increase of severity of the pattern. Variable decelerations are not good predictors of Apgar scores less than or equal to 6 at 1 minute, but late decelerations are predictive when they occur more than 20% of the time. The fetus with variable decelerations a normal pH can be observed through the first stage of labor with a high degree of confidence. However, when a 20% or more moderate-to-severe late deceleration/contraction ratio is present, intervention is necessary even if scalp blood pH is normal. The FHR deceleration/uterine contraction (UC) ratio is a simple bedside technique for assessing fetal outcome.     

Amniotic fluid index and prolonged antepartum fetal heart rate decelerations.

Both prolonged fetal heart rate (FHR) decelerations and decreased amounts of amniotic fluid (AF) have been associated with adverse fetal outcome. To determine whether adverse outcome could be predicted by a quantitative assessment of AF in patients with prolonged FHR decelerations, we identified 97 consecutive pregnancies found during antepartum testing to have prolonged FHR decelerations. A four-quadrant AF index was measured concurrently in 92 of these 97 patients. Women with an AF index less than 2 cm had operative intervention for fetal distress in seven of 11 cases (64%), compared with 17 of 81 (21%) who had an index of 2 cm or more (P = .005). We conclude that in patients with a prolonged FHR deceleration during antepartum testing, the need for operative intervention for fetal distress is increased when oligohydramnios is present.     

小于胎龄早产儿产时胎心电子监护图形特征及其临床意义

目的探讨小于胎龄早产儿胎心电子监护图形(CTG)特征及其临床意义。方法回顾性分析303例32~36孕周、无妊娠合并症的单纯胎膜早破和原因不明早产孕妇的全产程CTG。其中,小于胎龄早产儿78例(PSGA组),适于胎龄早产儿225例(PAGA组)。比较宫缩时两组CTG特征,合并症情况及分娩结局。结果PSGA组及PAGA组出现单纯U型变异减速的胎儿分别为24例(308%)和10例(44%),两组比较,差异有统计学意义(P<001);U型变异减速合并其他异常CTG的胎儿分别为10例(128%)和1例(04%),两组比较,差异也有统计学意义(P<001)。PSGA组,出现单纯U型变异减速者的难产率(208%)与胎心电子监护无异常者的难产率(227%)比较,差异无统计学意义(P>005),但与U型变异减速合并其他异常CTG者的难产率(600%)比较,差异有统计学意义(P<005)。PSGA组中,34例出现U形变异减速,其中合并脐带异常15例(绕颈、绕身14例、脐带过短1例),PSGA组44例无U形变异减速者中,合并脐带异常9例(绕颈、绕身),两组比较,差异有统计学意义(P<005)。结论U形变异减速是小于胎龄早产儿分娩过程中的特征性胎儿监护图形,但不是胎儿缺氧的征象,如不合并其他异常CTG,不需特殊处理。     

Characteristics of maternal heart rate patterns during labor and delivery

OBJECTIVE: To find patterns characteristic of maternal heart rates recorded by an electronic fetal monitor and compare them with concomitant fetal heart rate (FHR) patterns. METHODS: Maternal heart rates and FHRs during active labor and delivery were simultaneously recorded in 26 parturients with singleton pregnancies in vertex presentation. The FHRs were obtained by an external ultrasound transducer or via a spiral scalp electrode and maternal heart rates by a triple-wire cable with electrocardiographic electrodes attached to the chest. Representative tracings of 30-60 minutes duration were selected from all stages of labor and after delivery of the placenta. Quantitative assessments were carried out under guidelines from the National Institute of Child Health and Human Development after blinding the source of these tracings. Patterns were compared by appropriate statistical analyses. RESULTS: Baseline maternal heart rates were significantly lower and their variability significantly higher than FHRs during all stages of labor. Maternal heart rates showed no decelerations; the proportion of tracings with accelerations increased as labor advanced, most of them coinciding with uterine contractions or bearing down efforts. The FHRs had both decelerations and accelerations. However, tracings with only accelerations (and no decelerations) were observed in decreasing frequency as labor advanced. Maternal accelerations had higher amplitudes and longer durations than fetal accelerations, especially in the second stage of labor. CONCLUSION: Maternal heart rate patterns recorded by electronic fetal monitors closely resemble fetal patterns. Baseline "fetal bradycardia," the absence of decelerations in the second stage of labor, and marked accelerations coinciding with uterine contractions may suggest a maternal heart rate rather than an FHR recording.     

Maternal heart rate patterns in the first and second stages of labor

Objective. To analyze typical maternal heart rate (MHR) patterns in the first and second stages of labor. Design. Observational study. Setting. Tertiary care community hospital. Population. Normal term parturients with epidural anesthesia. Methods. Confirmed MHR and uterine activity were simultaneously recorded. The average MHR was analyzed 10 seconds before, as well as at the peak of, each contraction and/or pushing effort. Each woman contributed one datapoint at each time point to the analysis. Main outcome measure. Change in MHR during contractions. Results. First stage: 7.6±2.1 contractions per woman (n=18) were analyzed. Average MHR decreased during contractions: from 83±13 to 74±10bpm; p<0.001). In 56% (10/18) of the women, 'early' type decelerations were seen in at least 50% of contractions. Second stage: 3.5±1.5 contractions per woman. All women (n=15) showed MHR accelerations during every pushing effort (ΔMHR: +35±13bpm; 88±14 to 123±17bpm; p<0.001). MHR was persistently >100bpm in three women (17%) in the first stage, and in four women (27%) in the second stage. Peak MHR >140bpm occurred during pushing in 20%. Conclusion. Decreases in MHR during contractions in the first stage of labor can mimic fetal heart rate (FHR) accelerations as well as early type decelerations. Thus, first stage tracings with a low baseline and early type decelerations may be maternal in origin and FHR should be independently confirmed in such tracings. Because second stage MHR accelerations generally show greater amplitude than FHR accelerations, tracings with repetitive accelerations during contractions (especially when Δ >20bpm) should be considered MHR until proven otherwise.