Internal Fetal Heart Rate Monitoring Research Articles

Safety of Internal Electronic Fetal Heart Rate Monitoring During Labor

Abstract Objective: To investigate the safety and efficacy of internal electronic fetal heart rate (FHR) monitoring during labor. Methods: This was a retrospective case-control study, which was an analysis of monitoring FHR with a fetal scalp electrode or a Doppler probe (94 pregnant women per group). In the internal monitoring group, when the opening of the uterine orifice was ≥3 cm, the fetal scalp electrode was placed after natural or artificial rupture of the membrane. FHR was simultaneously monitored using a Doppler probe. In the external monitoring group, continuous FHR monitoring was performed using an ultrasound Doppler transducer fixed on the maternal abdomen. The toco transducer was used to record uterine contractions. Pathological examination of the placenta was performed prospectively in 49 and 48 cases in the internal electronic FHR monitoring group and control group, respectively. Maternal-infant outcomes (e.g. fever, puerperal infection, puerperal morbidity, delivery mode, Apgar score, and scalp injury) were recorded. Umbilical artery blood was extracted for blood gas analysis. Differences between the two groups were compared using the paired t-test, χ 2 test, Yates corrected χ 2 test or Fisher exact test. Results: Non-statistically significant differences between the internal and external monitoring groups were observed in the incidence of neonatal acidosis (1/94 (1.06%) vs. 3/94 (3.19%), respectively; χ 2 = 0.255, P = 0.613), cesarean section/operative vaginal delivery (8/94 (8.51%) vs. 15/94 (15.96%), respectively; χ 2 = 2.427, P = 0.181), fever during labor (18/94 (19.15%) vs. 15/94 (15.96%), respectively; χ 2 = 0.331, P = 0.565), puerperal morbidity (2/94 (2.13%) vs. 3/94 (3.19%), respectively; χ 2 = 0.000, P = 1.000), chorioamnionitis (9/49 (18.37%) vs. 7/48 (14.58%), respectively; χ 2 = 0.252, P = 0.616), and neonatal asphyxia (0/94 (0.00%) vs. 1/94 (1.06%), respectively; χ 2 = 0.000, P = 1.000). There were no puerperal infections, neonatal scalp injuries, or scalp abscesses found in either group. Using the internal monitoring value as reference, the incidence of FHR false deceleration in external FHR monitoring was 20.21% (19/94 women). Conclusion: Internal FHR monitoring during labor does not increase the incidence of adverse perinatal outcomes. External monitoring was associated with FHR false decelerations.

The Efficacy of In-Phase and Quadrature Demodulation in Electronic Fetal Heart Rate Monitoring During Labor

Abstract Objective: To investigate the efficacy of in-phase and quadrature (IQ) demodulation in electronic fetal heart rate monitoring (EFM) to reduce false reports of fetal heart rate (FHR) doubling or halving. Methods: This is a prospective cohort study. A total of 263 full-term pregnant women who delivered at Peking University Shenzhen Hospital between August 2019 and July 2020 were prospectively enrolled in the study. FHR monitoring began when the cervix was dilated to 2–3 cm and continued until delivery. Raw fetal Doppler audio signals and internal and external cardiotocography curves from internal electrode monitoring, EFM with conventional demodulation (external), and EFM with IQ demodulation (external) were acquired to compare FHR doubling and halving time. In cohort 1, FHR was compared between IQ demodulation and conventional demodulation. In cohort 2, FHR was compared between IQ demodulation, conventional demodulation, and internal FHR monitoring. Count data were statistically analyzed using the Chi-squared test, and measurement data were statistically analyzed using t-test for correlation coefficients, and Bland-Altman analysis for concordance ranges. Results: To compare IQ demodulation and conventional demodulation, 225 pregnant women were monitored for a total of 835,870 seconds. The beat-to-beat interval of FHRs in raw fetal Doppler audio signals was used as the reference. The results showed a doubling time of 3401 seconds (0.407%, 3401/835,870) and a halving time of 2918 seconds (0.349%, 2918/835,870) with conventional demodulation, compared to 241 seconds (0.029%, 241/835,870) and 589 seconds (0.070%, 589/835,870), respectively, with IQ demodulation. IQ demodulation reduced FHR doubling by approximately 93% (3160/3401) and FHR halving by approximately 80% (2329/2918) compared to conventional demodulation (P < 0.01). To compare IQ demodulation, conventional demodulation, and internal FHR monitoring, 38 pregnant women were monitored for a total of 98,561 seconds. FHR from internal electrode monitoring was used as the reference. The results showed a doubling time of 238 seconds (0.241%, 238/98,561) and a halving time of 235 seconds 0.238%, 235/98,561) with conventional demodulation, compared with 30 seconds (0.030%, 30/98,561) and 81 seconds (0.082%, 81/98,561), respectively, with IQ demodulation (P < 0.05). No significant difference was observed in doubling or halving time between IQ demodulation and internal FHR monitoring (P > 0.05). IQ demodulation was more closely correlated with internal FHR monitoring than conventional demodulation (0.986 vs. 0.947). The Bland-Altman analysis showed that the concordance range of IQ demodulation vs. internal FHR monitoring was significantly narrower than that of conventional demodulation vs. internal FHR monitoring ((−5.32,6.01) vs. (−10.87,11.46)). Conclusion: EFM with IQ demodulation significantly reduces false FHR doubling and halving, with an efficacy similar to that of internal FHR monitoring.

Differences between external and internal fetal heart rate monitoring during the second stage of labor: a prospective observational study

To compare fetal heart rate (FHR) signals acquired simultaneously by an external ultrasound probe and a scalp electrode during the second stage of labor. This was a prospective observational study in a labor ward of a tertiary care university hospital. The population was women in labor with uneventful singleton pregnancies at term. Simultaneous external and internal FHR monitoring was performed in 67 consecutively recruited women during the second stage of labor. Cases were subsequently excluded if the trace length was under 40 min, cesarean birth occurred, or the interval between trace-end and birth exceeded 5 min, leaving a total of 33 traces for analysis. The last 40-60 min of these traces were analyzed by a computer system (Omniview-SisPorto 3.5; Speculum, Lisbon, Portugal) to quantify cardiotocographic parameters. Paired sample t-test and Bland-Altman limits of agreement (LoA) were used for statistical analysis, setting significance at 0.05. The main outcome measures were signal loss, FHR baseline, periodic events, and percentage of periodic events coinciding with contractions. A higher signal loss was observed with external monitoring [10% vs. 4%; P<0.001, LoA=(-6, 18)]. No differences were found in mean FHR baseline [129 bpm vs. 130 bpm, P=0.245, LoA=(-15, 12)], but more accelerations [12 vs. 8, P<0.001, LoA=(-5, 13)] and less decelerations [8 vs. 10, P<0.001, LoA=(-8, 4)] were detected with external monitoring. With this method there were also more accelerations (66% vs. 55%, P=0.036) and less decelerations (68% vs. 81%, P=0.017) coinciding with contractions. External FHR monitoring during the second stage of labor results in higher signal loss, increased number of accelerations, and decreased number of decelerations when compared with internal monitoring.

Oxytocin for prelabour rupture of membranes at or near term.

Induction of labour after prelabour rupture of membranes may reduce the risk of neonatal infection. The objective of this review was to assess the effects of induction of labour with oxytocin versus expectant management for prelabour rupture of membranes at or near term (34 weeks or more). We searched the Cochrane Pregnancy and Childbirth Group trials register. Randomised and quasi-randomised trials of early use of oxytocin versus no early use of oxytocin for spontaneous rupture of membranes, before labour (34 weeks gestation or more). Trials were assessed for quality and data were abstracted. Eighteen studies were included. The trials were of variable quality with potential for significant bias. Compared to expectant management, induction of labour by oxytocin was associated with a decreased risk of maternal infection (odds ratio for chorioamnionitis of 0.63, 95% confidence interval 0.51 to 0.78, endometritis 0.72, 95% confidence interval 0.52 to 0.99). There was also a decreased risk of neonatal infection (odds ratio 0.64, 95% confidence interval 0.44 to 0.93). The size of this effect may have been biased in favour of oxytocin. Based on one trial, women were more likely to view their care positively if labour was induced with oxytocin. Caesarean section rates were not statistically different between groups, although the trend was towards fewer interventions with expectant management. Oxytocin was associated with more frequent use of pain relief and internal fetal heart rate monitoring. Perinatal mortality rates were low and not significantly different between groups, although the trend was towards fewer deaths with induction of labour by oxytocin. Induction of labour by oxytocin may decrease the risk of maternal and neonatal infection compared to expectant management. Induction of labour with oxytocin does not appear to increase the rate of caesarean section, although it may increase use of pain relief and internal fetal heart rate monitoring.

Prostaglandins versus oxytocin for prelabour rupture of membranes at term.

The conventional method of induction of labour is with intravenous oxytocin. More recently, induction with prostaglandins, followed by an infusion of oxytocin if necessary, has been used. The objective of this review was to assess the effects of induction of labour with prostaglandins versus oxytocin for prelabour rupture of membranes at term. We searched the Cochrane Pregnancy and Childbirth Group trials register. Randomised and quasi-randomised trials of early stimulation of uterine contractions with prostaglandins (with or without oxytocin) versus with oxytocin alone (not combined with prostaglandins) in women with spontaneous rupture of membranes at term (37 weeks or more gestation). Two reviewers assessed trial quality and extracted data. Eight trials were included. Based on three trials, prostaglandins compared to oxytocin were associated with increased chorioamnionitis (odds ratio of 1.51, 95% confidence interval 1.07 to 2.12) and neonatal infections (odds ratio 1.63, 95% confidence interval 1.00 to 2.66). Based on four trials, prostaglandins were associated with a decrease in epidural analgesia (odds ratio of 0.86, 95% confidence interval 0.73 to 1.00) and internal fetal heart rate monitoring (based on one trial). Caesarean section, endometritis and perinatal mortality were not significantly different between the groups. Women with prelabour rupture of membranes at term having their labour induced with prostaglandins appear to have a lower risk of epidural analgesia and fetal heart rate monitoring. However there appears to be an increased risk of chorioamnionitis and neonatal infections after prostaglandin induction compared to oxytocin.

Prostaglandins versus oxytocin for prelabour rupture of membranes at or near term.

The conventional method of induction of labour is with intravenous oxytocin. More recently, induction with prostaglandins, followed by an infusion of oxytocin if necessary, has been used. The objective of this review was to assess the effects of induction of labour with prostaglandins compared with oxytocin, at or near term. We searched the Cochrane Pregnancy and Childbirth Group trials register. Randomised and quasi-randomised trials of early stimulation of uterine contractions with prostaglandins (with or without oxytocin) versus with oxytocin alone (not combined with prostaglandins) in women with spontaneous rupture of membranes before labour (34 weeks or more gestation). Two reviewers assessed trial quality and extracted data. Seventeen trials were included. Most of the trials were of moderate to good quality. Based on six trials, prostaglandins compared with oxytocin were associated with increased chorioamnionitis (odds ratio of 1.49, 95% confidence interval 1.07 to 2.09) and maternal nausea/vomiting. Based on eight trials, prostaglandins were associated with a decrease in epidural analgesia, odds ratio of 0.85, 95% confidence interval 0.73 to 0.98 and internal fetal heart rate monitoring (based on one trial). Caesarean section, endometritis and perinatal mortality were not significantly different between the groups. Women with prelabour rupture of membranes at or near term having their labour induced with prostaglandins appear to have a lower risk of epidural analgesia and fetal heart rate monitoring. However there appears to be an increased risk of chorioamnionitis and nausea/vomiting with prostaglandins compared to oxytocin.

Perinatal factors influencing survival at twenty-four weeks' gestation

Our objective was to identify those obstetric and neonatal factors associated with survival in infants delivered at 24 weeks' gestation. The obstetric and pediatric data bases from the two hospitals in our perinatal center were examined to ascertain all infants delivered between 1987 and 1989 whose gestational age was 24 weeks to 24 weeks 6 days. This time interval was chosen to coincide with the introduction of prophylactic exogenous surfactant. Data were abstracted from the maternal antepartum and intrapartum records and the neonatal records, with specific attention to objective risk factors related to survival. Forty-five pregnant patients were identified and delivered of 52 infants. Seventeen newborn infants survived (33%). Univariate comparisons between survivors and nonsurvivors revealed more aggressive intrapartum care in the former cohort as represented by the frequencies of internal fetal heart rate monitoring (p = 0.005), maternal oxygen therpay (p = 0.003), and maternal position change to remediate decelerations (p = 0.001). Planned exclusion of cesarean delivery was more common in those pregnancies that ended in fetal or neonatal death (29/35 vs 7/17; p = 0.006). Although a greater proportion of infants delivered by cesarean section survived (6/11 vs 11/41), this difference was not significant (p = 0.17). With the use of logistic regression, the best predictor of survival was gestational age at delivery. Neonatal care was more aggressive among survivors, as measured by the relative frequencies of resuscitation and surfactant administration. Respiratory distress syndrome was either absent (n = 6) or mild (n = 6) in a majority of the survivors, and respiratory insufficiency was the major cause of neonatal death. Perinatal outcome at 24 weeks' gestation appears most dependent on gestational age at delivery. The intensity of intrapartum care and neonatal support, as well as clinical biases regarding survivability, may also influence outcome.