Computerized analysis of fetal heart rate parameters by gestational age

Effect of maternal cortisol levels on fetal heart rate patterns in primiparous pregnant women in the third trimester

OBJECTIVE

This study aimed to determine whether maternal cortisol levels affect fetal heart rate patterns in primiparous pregnant women in the third trimester.

METHODS

This cross-sectional descriptive study included 400 primiparous pregnant women with uncomplicated pregnancies between November and December 2022. The study included primiparous pregnant women over 18 years old in the third trimester who had not exercised for at least 2 h before the fetal heart rate monitoring and had a healthy pregnancy without consuming any food or drink. Fetuses with decelerating heartbeats and pregnant women who showed uterine contraction and cervical dilation during the fetal heart rate monitoring were excluded from the study. Research data were collected with the data collection form. The fetal heart rate data were collected using a cardiotocograph. At least two accelerations during the 20-min nonstress test period were the basis for diagnosing a reactive nonstress test. About 5 mL of maternal saliva for cortisol measurements was collected before fetal heart rate monitoring. Research data were analyzed with IBM SPSS Statistics for Macintosh, Version 28.0. A p-value of <0.05 was considered significant.

RESULTS

There were no significant differences in the comparison of the groups in terms of education and income status, family type, fetal gender, pregnancy planning status, BMI and age averages, or gestational week averages (p>0.05). The number of at least two accelerations required for the diagnosis of reactive NST was also higher in Group 1 (maternal salivary cortisol level ≤24.20). A moderately positive relationship between fetal heart rate and maternal salivary cortisol was observed (r=0.448, p=0.000). In total, 11.9% of the total change in fetal heart rate level is explained by maternal cortisol (R2=0.119). Maternal cortisol increases fetal heart rate level (ß=0.349).

CONCLUSION

These findings suggest that stress in primiparous pregnant women with high cortisol levels may influence fetal heart rate patterns. It was revealed that the increase in cortisol level, considered a stress hormone, may be a harbinger of fetal tachycardia.

Characteristics of Heart Rate Tracings in Preterm Fetus

Background and Objectives: Prematurity is currently a serious public health issue worldwide, because of its high associated morbidity and mortality. Optimizing the management of these pregnancies is of high priority to improve perinatal outcomes. One tool frequently used to determine the degree of fetal wellbeing is cardiotocography (CTG). A review of the available literature on fetal heart rate (FHR) monitoring in preterm fetuses shows that studies are scarce, and the evidence thus far is unclear. The lack of reference standards for CTG patterns in preterm fetuses can lead to misinterpretation of the changes observed in electronic fetal monitoring (EFM). The aims of this narrative review were to summarize the most relevant concepts in the field of CTG interpretation in preterm fetuses, and to provide a practical approach that can be useful in clinical practice. Materials and Methods: A MEDLINE search was carried out, and the published articles thus identified were reviewed. Results: Compared to term fetuses, preterm fetuses have a slightly higher baseline FHR. Heart rate is faster in more immature fetuses, and variability is lower and increases in more mature fetuses. Transitory, low-amplitude decelerations are more frequent during the second trimester. Transitory increases in FHR are less frequent and become more frequent and increase in amplitude as gestational age increases. Conclusions: The main characteristics of FHR tracings changes as gestation proceeds, and it is of fundamental importance to be aware of these changes in order to correctly interpret CTG patterns in preterm fetuses.

Maternal Serotonin Reuptake Inhibitor Antidepressants Have Acute Effects on Fetal Heart Rate Variability in Late Gestation

Background: Prenatal exposure to serotonin reuptake inhibitor (SRI) antidepressants increases risk for adverse neurodevelopmental outcomes, yet little is known about whether effects are present before birth. In relation to maternal SRI pharmacokinetics, this study investigated chronic and acute effects of prenatal SRI exposure on third-trimester fetal heart rate variability (HRV), while evaluating confounding effects of maternal depressed mood. Methods: At 36-weeks' gestation, cardiotocograph measures of fetal HR and HRV were obtained from 148 pregnant women [four groups: SRI-Depressed (n = 31), SRI-Non-Depressed (n = 18), Depressed (unmedicated; n = 42), and Control (n = 57)] before, and ~5-h after, typical SRI dose. Maternal plasma drug concentrations were quantified at baseline (pre-dose) and four time-points post-dose. Mixed effects modeling investigated group differences between baseline/pre-dose and post-dose fetal HR outcomes. Post hoc analyses investigated sex differences and dose-dependent SRI effects. Results: Maternal SRI plasma concentrations were lowest during the baseline/pre-dose fetal assessment (trough) and increased to a peak at the post-dose assessment; concentration-time curves varied widely between individuals. No group differences in fetal HR or HRV were observed at baseline/pre-dose; however, following maternal SRI dose, short-term HRV decreased in both SRI-exposed fetal groups. In the SRI-Depressed group, these post-dose decreases were displayed by male fetuses, but not females. Further, episodes of high HRV decreased post-dose relative to baseline, but only among SRI-Non-Depressed group fetuses. Higher maternal SRI doses also predicted a greater number of fetal HR decelerations. Fetuses exposed to unmedicated maternal depressed mood did not differ from Controls. Conclusions: Prenatal SRI exposure had acute post-dose effects on fetal HRV in late gestation, which differed depending on maternal mood response to SRI pharmacotherapy. Importantly, fetal SRI effects were sex-specific among mothers with persistent depressive symptoms, as only male fetuses displayed acute HRV decreases. At trough (pre-dose), chronic fetal SRI effects were not identified; however, concurrent changes in maternal SRI plasma levels suggest that fetal drug exposure is inconsistent. Acute SRI-related changes in fetal HRV may reflect a pharmacologic mechanism, a transient impairment in autonomic functioning, or an early adaption to altered serotonergic signaling, which may differ between males and females. Replication is needed to determine significance with postnatal development.

Intrapartum fetal heart rate between 150 and 160 bpm at or after 40 weeks and labor outcome

INTRODUCTION

A baseline fetal heart rate between 110 and 160 bpm is considered normal. However, among normal fetuses the average baseline heart rate has been shown to diminish progressively and the 90th centile of the fetal heart rate at 40 weeks of gestation has been consistently found at around 150 bpm. The aim of our study was to assess the labor and neonatal outcome of fetuses at 40 gestational weeks or beyond, whose intrapartum baseline fetal heart rate was between 150 and 160 bpm.

MATERIAL AND METHODS

Retrospective cohort study including singleton pregnancies with spontaneous onset of labor, gestational age between 40⁺⁰ and 42⁺⁰ weeks, category I CTG trace according to the FIGO guidelines 2015 with baseline fetal heart rate between 110 and 160 bpm during the first 60 minutes of active labor. Exclusion criteria were maternal hyperpyrexia at admission, fetal arrhythmias, maternal tachycardia (>110 bpm) and uterine tachysystole (>5 contractions/10 minutes). The following outcomes were compared between fetuses with a baseline ranging between 110 and 149 bpm and those with a baseline ranging between 150 and 160 bpm: incidence of meconium-stained amniotic fluid, intrapartum hyperpyrexia, mode of delivery, Apgar at 5 minutes <7, arterial pH <7.1 and Neonatal Intensive Care Unit admission, incidence of a composite adverse neonatal outcome.

RESULTS

In all, 1004 CTG traces were included in the analysis, 860 in Group 110-149 bpm and 144 in Group 150-160 bpm. Group 150-160 bpm had a significantly higher incidence of meconium-stained amniotic fluid (odds ratio [OR] 2.6; 95% CI 1.8-3.8), maternal intrapartum hyperpyrexia (OR 4.7; 95% CI 1.1-14.6), urgent/emergent cesarean section for suspected fetal distress (OR 13.4; 95% CI 3.3-54.3), Apgar <7 at 5th min (OR 9.13; 95% CI 1.5-55.1) and neonatal acidemia (OR 3.5; 95% CI 1.5-55.1). Logistic regression including adjustiing for potential confounders showed that fetal heart rate between 150 and 160 bpm is an independent predictor of meconium-stained amniotic fluid (adjusted odds ratio [aOR] 2.2; 95% CI 1.5-3.3), cesarean section during labor for fetal distress (aOR 10.7; 95% CI 2.9-44.6), neonatal acidemia (aOR 2.6; 95% CI 1.1-6.7) and adverse composite neonatal outcome (aOR 2.6; 95% CI 1.2-5.6).

CONCLUSIONS

In fetuses at 40 weeks or beyond, an intrapartum fetal heart rate baseline ranging between 150 and 160 bpm seems associated with a higher incidence of labor complications.

Fetal heart rate, heart rate variability, and heart rate/movement coupling in the Safe Passage Study

OBJECTIVE

To determine normative values for heart rate patterns in healthy fetuses.

METHODS

This research is from the Safe Passage Study conducted by the Prenatal Alcohol and SIDS and Stillbirth (PASS) Network. A standardized protocol assessed fetal heart rate (FHR), heart rate variability (HRV), and movement from 1655 fetuses at three-time points during gestation (20-24 weeks, 28-32 weeks, 34-38 weeks gestation).

RESULTS

FHR decreased while HRV increased over gestation. At the latter two ages, males had significantly lower FHR than females while there were no sex differences in FHR at 20-24 weeks. When accounting for the fetal state during late gestation (34-28 weeks), we found that males had significantly lower FHR than females in the active fetal state only.

CONCLUSION

Results demonstrate significant state, gestational age, and sex-related changes in cardiac activity, somatic activity, and autonomic function as the fetus approaches birth.

Longitudinal changes of cardiotocographic parameters throughout pregnancy: a prospective cohort study comparing small-for-gestational-age and normal fetuses from 24 to 40 weeks

OBJECTIVE

To compare longitudinal trends of cardiotocographic (CTG) parameters between small-for-gestational-age (SGA) and normal fetuses, from 24 to 41 weeks of pregnancy.

METHODS

A prospective cohort study was carried out in singleton pregnancies without fetal malformations. At least one CTG was performed in each of the following intervals: 24-26 weeks+6 days, 27-29 weeks+6 days, 30-32 weeks+6 days, 33-35 weeks+6 days, 36-38 weeks+6 days and ≥39 weeks. Tracings were analyzed using the Omniview-SisPorto® 3.6 system. Cases with a normal pregnancy outcome, including a birthweight ≥10th percentile for gestational age, were compared with two groups of SGA fetuses: with birthweight <10th percentile (SGA<p10) and <3rd percentile (SGA<p3; a subgroup of the latter). Generalized linear mixed-effects models were used for analysis.

RESULTS

A total of 176 fetuses (31 SGA) and 1256 tracings (207 from SGA fetuses) were evaluated. All CTG parameters changed significantly throughout pregnancy in the three groups, with a decreasing baseline and probability of decelerations, and an increasing average long-term variability (LTV), average short-term variability (STV) and accelerations. Baseline showed a more pronounced decrease (steeper slope) in SGA fetuses, being higher in these cases at earlier gestational ages and lower later in pregnancy. Average LTV was significantly lower in SGA<p3 fetuses, but a parallel increase occurred in all groups. There was a considerable inter-fetal variability within each group.

CONCLUSION

A unique characterization of CTG trends throughout gestation in SGA fetuses was provided. A steeper descent of the baseline was reported for the first time. The findings raise the possibility of clinical application of computerized CTG analysis in screening and management of fetal growth restriction.

Cardiotocographic parameters in small-for-gestational-age fetuses: How do they vary from normal at different gestational ages? A study of 11687 fetuses from 25 to 40 weeks of pregnancy

AIM

The aim of this study was to assess how cardiotocographic (CTG) parameters differ between small-for-gestational-age (SGA) and normal fetuses at different gestational ages.

METHODS

This was a retrospective cross-sectional study using the first antepartum tracing of singleton pregnancies with no malformations. Fetuses with birthweight ≥10th percentile for gestational age and other normal pregnancy outcome criteria (term birth, normal umbilical artery pH and Apgar scores, no intensive care unit admission) were compared with fetuses with birthweight <10th and <3rd percentiles for gestational age (SGA < p10 and SGA < p3, a subgroup of the latter). Each CTG parameter was compared, by gestational age, using both statistical tests and percentile curves derived from normal outcome cases. Tracings were analyzed with the OmniviewSisPorto® 3.7 system.

RESULTS

A total of 11 687 tracings (from the same number of fetuses) were analyzed: 9701 normal, 1986 SGA < p10, and 543 SGA < p3. SGA fetuses had lower long- and short-term variability, and number of accelerations, with more pronounced differences between around 28 and 35 weeks. In contrast, baseline was lower in SGA fetuses from 34 weeks onwards. All differences were more pronounced for SGA < p3 fetuses. Similar trends throughout gestation occurred in all groups: decrease in baseline, and increase in long- and short-term variability, and accelerations.

CONCLUSIONS

This study represents an important step for accurate CTG interpretation in SGA fetuses and, consequently, management of fetal growth restriction (FGR), as it contributes to differentiate between maturational CTG changes that occur physiologically throughout pregnancy, and possible signs of fetal compromise in FGR.

Computerised analysis of antepartum foetal heart parameters: New reference ranges

We selected 4012 cCTG records (one trace for each patient) performed in healthy pregnancies from 30th to 42nd gestational week using foetal heart rate (FHR), short-term variability (STV), long-term irregularity (LTI), Delta, approximate entropy (ApEn), spectral components as low frequency (LF), median frequency (MF), high frequency (HF) and LF/(HF + MF) ratio were analysed. Reference nomograms were created and sensitivity and specificity for the prediction of foetal compromise were calculated which were 90% and 89%, respectively. Changes of cCTG parameters according to gestational week were evaluated: FHR (r = -.65) and LF (r = -.87) showed a statistically significant reduction (p < .05) with gestational age. STV (r = .59), LTI (r = .69), Delta (r = .67), and MF (r = .88) showed a statistically significant increase (p < .05) with gestational age. In contrast, for ApEn (r = -.098), HF (r = .14) and LF/(HF + MF) ratio (r = -.47) a non-statistically significant change was found (p > .05). The identification of reference ranges for cCTG indexes in according to gestational age could provide a more objective examination of cCTG trace.

Values of T/QRS ratio in pregnancies complicated by intrauterine growth restriction

AIMS

To evaluate values of T/QRS ratio in normal pregnancies and those complicated by intrauterine growth restriction (IUGR) using non-invasive method with transabdominal electrodes. Assessment of fetal well-being in IUGR pregnancies.

METHODS

Fetal electrocardiograms were recorded and analyzed by KOMPOREL software from ITAM (Zabrze, Poland) and T/QRS ratios were automatically calculated. Doppler velocimetry of the middle cerebral artery and umbilical artery was carried out. The study group consisted of IUGR pregnancies with normal cerebroplacental ratios (CPRs) (n=110), IUGR pregnancies with decreased CPRs (n=29), and healthy controls (n=549). Analyses were performed between the study groups and by gestational age. T/QRS ratio variables and CPRs were calculated. Analysis of variance and linear regression were performed.

RESULTS

Maximum values, maximum minimal value differences, and standard deviations of T/QRS ratio were significantly different between the IUGR group with reduced CPRs and normal CPRs (P=0.0009, P=0.0000, P=0.0034, respectively) as well as between the IUGR group with reduced CPRs and healthy controls (P=0.0000, P=0.0001, P=0.0009, respectively). Mean maximum values in the IUGR group with reduced CPRs exceeded normal values.

CONCLUSIONS

T/QRS ratio may be useful in assessing fetal well-being in IUGR pregnancies; however, future studies are needed to determine typical ranges of T/QRS ratio in pregnancies complicated by IUGR.

Longitudinal evaluation of computerized cardiotocographic parameters throughout pregnancy in normal fetuses: a prospective cohort study

INTRODUCTION

The longitudinal cardiotocographic (CTG) changes throughout pregnancy in normal fetuses have never been fully described. We aimed at characterizing the evolution of CTG parameters in healthy fetuses, from 24 to 41 weeks of gestation.

MATERIAL AND METHODS

A prospective cohort study was conducted in singleton fetuses without structural abnormalities on second-trimester ultrasound. At least one CTG was performed in each of the following intervals: 24-26 weeks(+6d) , 27-29 weeks(+6d) , 30-32 weeks(+6d) , 33-35 weeks(+6d) , 36-38 weeks(+6d) and ≥39 weeks; tracings were analyzed by the OMNIVIEW-SISPORTO 3.6 system. Cases of preterm delivery, fetal death, birthweight under the 10th percentile, low five-minute Apgar, umbilical artery acidemia or neonatal intensive care unit admission were subsequently excluded.

RESULTS

A total of 1049 eligible tracings were obtained from 145 fetuses. There was a significant increase over time in average long-term variability (LTV), average short-term variability (STV), number of accelerations and uterine contractions. Conversely, fetal heart rate (FHR) baseline and number of decelerations decreased. A high inter-fetal variability was observed, but there was considerable intra-fetal consistency. Fetuses showing a marked decrease in FHR baseline and those with a marked increase in average LTV had a significantly lower birthweight. Cesarean section rate was significantly higher in cases with a decrease in average STV throughout gestation.

CONCLUSIONS

This prospective longitudinal study shows an evolution in computerized CTG parameters during pregnancy, indicating the need to adapt interpretation criteria based on gestational age. The high inter-fetal variability and considerable intra-fetal consistency suggests the possible value of using each fetus as its own reference in serial assessments.

Sex-related differences in the development of fetal heart rate dynamics

BACKGROUND

Despite previous efforts to explain the general advantages of female fetuses over males regarding health, sex-related differences in the dynamics or complexity of fetal heart rate (FHR) variability and FHR maturation patterns have not yet been identified.

AIM

To make linear and nonlinear comparisons of antepartum FHR indices, dynamics, complexity, and reactivity to the non-stress test (NST) and vibroacoustic-stimulation test (VAST) in male and female fetuses.

STUDY DESIGN

A total of 3835 singleton term deliveries without maternal and fetal complications were divided into female (n=1849) and male (n=1986) groups, and subjected to comparison and analyses.

SUBJECTS

Linear FHR indices, approximate entropy (ApEn), sample entropy (SampEn), short-term/long-term exponents (α1/α2), correlation dimension (CD), NST and VAST criteria, and modified nonlinear reactive criteria (MNRC) were used to evaluate outcomes.

RESULTS

ApEn was consistently higher in female fetuses than in male ones. ApEn in female fetuses was maximal at 29-30 gestational weeks, while the increase in ApEn was delayed in male fetuses but more rapid, reaching its peak at 31-32 gestational weeks. In both sexes, CD increased up to term, and α2 rapidly decreased up to 31-32weeks in an analogous manner. The two sexes differed significantly in response to VAST at <31 gestational weeks and there was a structural difference in reactive patterns under MNRC.

CONCLUSIONS

Female fetuses exhibit greater heart rate dynamics in early gestational periods, suggesting that their cardiovascular system matures earlier than that of males. Male fetuses undergo a compensatory period of rapid change to catch up with females at term.

Complex and irregular heart rate dynamics in fetuses compromised by maternal anemia as a high-risk pregnancy

AIM

To examine how complex and irregular fetal heart rate (FHR) dynamics differ between fetuses of normal pregnancies and those of pregnancies complicated by maternal anemia (MA), and to place this in the context of high-risk pregnancies.

METHODS

Our study population consisted of 97 pregnant women affected by MA, 118 affected by pregnancy-induced hypertension (PIH), 88 affected by gestational diabetes mellitus (GDM), 53 with preterm premature rupture of membranes (pPROM), and 356 normal pregnancies as controls. We calculated approximate entropy (ApEn), sample entropy (SampEn), and correlation dimension (CD) to quantify irregularity and the chaotic dynamics of each FHR time series.

RESULTS

The ApEn in the fetuses of the MA and PIH groups was significantly lower than that of the normal controls (P<0.05). The SampEn was significantly lower in the high-risk groups, except for the pPROM group, than in the normal controls (P<0.05). The CD in the PIH and severe MA groups was significantly lower than that of the normal controls (P<0.05, respectively). In the MA group, the dynamic indices showed a highly significant positive correlation with hemoglobin (Hb) levels (P<0.0001).

CONCLUSION

The decreased complexity and/or irregularity in the FHR from pregnancies with MA may reflect abnormalities in the complex, integrated cardiovascular control. The irregularity and complexity of the FHR increased together with Hb levels in pregnancies with MA. Our data suggest that the integrity of the nervous system in the fetuses compromised by severe MA might result directly in adverse outcomes.

Nonlinear analysis of fetal heart rate dynamics in fetuses compromised by asymptomatic partial placental abruption

INTRODUCTION

We analyzed fetal heart rate (FHR) parameters, dynamics, and outcomes in pregnancies with asymptomatic partial placental abruption (PPA) compared with those in normal pregnancies.

METHODS

We examined nonstress test (NST) data acquired from 2003 to 2012 at our institution. Normal pregnancies (N = 170) and PPA cases (N = 17) were matched for gestational age, fetal sex, and mean FHR. NSTs were performed at 33-42 weeks of gestation. FHR parameters obtained from the NST and perinatal outcomes were analyzed using linear methods. Nonlinear indices, including approximate entropy (ApEn), sample entropy (SampEn), short-term and long-term scaling exponents (α1 and α2), and correlation dimension (CD), were used to interpret FHR dynamics and system complexity. The area under a receiver operating characteristic curve (AUC) was used to evaluate the nonlinear indices.

RESULTS

There were no significant differences in general characteristics and FHR parameters between the PPA and control groups. However, gestational age at delivery, birth weight, 5-min Apgar scores, ApEn, SampEn, and CD were significantly lower in the PPA group than in the control group (P < 0.05). The long-term scaling exponent (α2) and crossover index (α2/α1) of the PPA fetuses were significantly higher than those of the controls (P < 0.01). A multiple regression model showed better performance in predicting PPA (AUC, 0.92; sensitivity 82.35%; specificity, 94.12%).

DISCUSSION

Nonlinear dynamic indices of FHR in asymptomatic PPA were qualitatively different from those in normal pregnancies, whereas the conventional FHR parameters were not significantly different.

Transient accelerations of fetal heart rate analyzed by computerized cardiotocography in the third trimester of pregnancy

OBJECTIVE

The aim of this study was to investigate the patterns of transient FHR accelerations (10 bpm and 15 bpm) in the third trimester of pregnancy, comparing the occurrence of this event before and after the 32nd gestational week.

METHODS

This is a prospective study comparing the results of the computerized cardiotocography of 46 low-risk women with singleton pregnancies, maternal age between 18 and 40 years, gestational age between 28 and 40 weeks, absence of maternal morbidity and adequate fetal growth according to ultrasound. Computed Cardiotocography (8002 Sonicaid System and Fetal Care System) was performed for 30 minutes to analyze the variables of FHR.

RESULTS

Twenty-three pregnant women underwent cardiotocography before 32 weeks (mean = 29.9 weeks, SD = 1.4 weeks) and were compared with 23 pregnant women who were examined after 32 weeks (mean = 36.3 weeks, SD = 2.5 weeks). Regarding the characteristics of FHR, fetuses evaluated between 32 1/7 weeks and 40 weeks showed a significantly greater number of accelerations above 15 bpm (median = 5, variation 0-18) than the group of pregnant women from 28 to 32 weeks (median = 4, variation 0 to 10; P = 0.048). There was a significant positive correlation between the number of accelerations above 15 bpm and the gestational age at examination (rho = 0.33; P = 0.026).

CONCLUSION

Computerized cardiotocography showed an association regarding the number of transient accelerations greater than 15 bpm in the assessment of both periods before and after 32 weeks of gestational age, suggesting the influence of the maturation of the fetal autonomic nervous system with pregnancy progression.

Open access intrapartum CTG database

Background

Cardiotocography (CTG) is a monitoring of fetal heart rate and uterine contractions. Since 1960 it is routinely used by obstetricians to assess fetal well-being. Many attempts to introduce methods of automatic signal processing and evaluation have appeared during the last 20 years, however still no significant progress similar to that in the domain of adult heart rate variability, where open access databases are available (e.g. MIT-BIH), is visible. Based on a thorough review of the relevant publications, presented in this paper, the shortcomings of the current state are obvious. A lack of common ground for clinicians and technicians in the field hinders clinically usable progress. Our open access database of digital intrapartum cardiotocographic recordings aims to change that.

Description

The intrapartum CTG database consists in total of 552 intrapartum recordings, which were acquired between April 2010 and August 2012 at the obstetrics ward of the University Hospital in Brno, Czech Republic. All recordings were stored in electronic form in the OB TraceVue®;system. The recordings were selected from 9164 intrapartum recordings with clinical as well as technical considerations in mind. All recordings are at most 90 minutes long and start a maximum of 90 minutes before delivery. The time relation of CTG to delivery is known as well as the length of the second stage of labor which does not exceed 30 minutes. The majority of recordings (all but 46 cesarean sections) is – on purpose – from vaginal deliveries. All recordings have available biochemical markers as well as some more general clinical features. Full description of the database and reasoning behind selection of the parameters is presented in the paper.

Conclusion

A new open-access CTG database is introduced which should give the research community common ground for comparison of results on reasonably large database. We anticipate that after reading the paper, the reader will understand the context of the field from clinical and technical perspectives which will enable him/her to use the database and also understand its limitations.

Comparison of fetal heart rate patterns using nonlinear dynamics in breech versus cephalic presentation at term

BACKGROUND

It has been reported that breech fetuses have inferior neurological outcomes regardless of mode of delivery, raising the possibility that in utero neurological impairment is more frequent in breech fetuses, possibly contributing to malpresentation.

AIMS

To assess differences between the cardiovascular autonomic nervous systems (ANSs) of breech and cephalic fetuses using nonlinear dynamic indices of fetal heart rate (FHR) variability.

STUDY DESIGN AND SUBJECTS

This study included 86 fetuses with breech presentation and 173 fetuses with cephalic presentation, with no other maternal or fetal problems. We analyzed FHR variability and spectral indices as markers of ANS behavior. We used nonlinear dynamic indices to represent the complexity of heart rate regulation, as well as correlation dimension as a chaotic index of the cardiovascular control system.

RESULTS

One of FHR parameters (Mean minute range) was significantly lower in breech than cephalic fetuses (p=0.0294). However, there were no other significant differences in any linear or nonlinear indices, nor in clinical outcomes, between breech and cephalic fetuses.

CONCLUSION

Our data suggest that breech fetuses have neither more active ANS nor less active complexity control systems than do cephalic fetuses. This indicates that the neurologic maturation of breech fetuses is not inferior to cephalic ones. The practical implication of these findings is that the nervous system integrity of breech fetuses may not result directly in neonatal complications.

The significance of amplitude and duration of fetal heart rate acceleration in non-stress test analysis

OBJECTIVE

This study was conducted to assess the relative significance of the amplitude versus the duration of accelerations in non-stress test (NST) analysis.

MATERIALS AND METHODS

A total of 3055 normal fetal heart rate (FHR) tracings at 30-42 weeks' gestation were analyzed by automated FHR analyzing software. Accelerations were classified as one of four combinations of amplitude and duration: 15 bpm-15 seconds (Acc15-15), 15 bpm-10 seconds (Acc15-10), 10 bpm-15 seconds (Acc10-15) and 10 bpm-10 seconds (Acc10-10). We estimated the correlation among the FHR acceleration combinations using correlation analysis based on linear regression models.

RESULTS

Linear regression models demonstrated statistically significant linear associations between Acc15-15 and Acc15-10 (r(2) = 0.998, p < 0.0001) and between Acc10-10 and Acc10-15 (r(2) = 0.989, p < 0.0001). There was significant association based on amplitude and relatively low correlation based on duration (Pearson correlation coefficient = 0.99 between Acc10-10 and Acc10-15, and 0.99 between Acc15-15 and Acc15-10). In the relationships of the FHR-work values, amplitude was a more important component of FHR acceleration than duration [Acc10-10 (1.67 beat) < Acc10-15 (2.50 beats) = Acc15-10 (2.50 beats) < Acc15-15 (3.75 beats)].

CONCLUSION

Amplitude was a more significant component of FHR acceleration than duration in the computerized analysis of NST.

Fetal heart rate regresses toward the mean in the third trimester

The purpose of this study was to investigate the feasibility of different fetal heart rate (FHR) ranges in the nonstress test (NST) and to better understand the meaning of mild bradycardia and/or tachycardia without non-reassuring patterns. We employed the heredity to show that mild bradycardia (100-119 beats per minute, bpm) and mild tachycardia (161-180 bpm) regressed to the normal FHR range (120-160 bpm). We used linear regression to analyze FHR data from FHR tracings recorded 10 min before (NST, as the predictor) and 10 min after vibroacoustic stimulation testing (as the dependent variable). Acceleration for 15 bpm-15 seconds (Acc1515) and deceleration for 15 bpm-15 seconds (Dec1515) in the NST were also analyzed for each group. The slope of the best-fit line was the largest in the mild bradycardia group and the smallest in the normal range group. Dec1515 was most prominent in mild tachycardia and both the mild bradycardia and tachycardia groups regressed towards the mean FHR range. Therefore, we propose that both mild bradycardia and tachycardia of FHR in non-acute situations (range between 100 and 180 bpm) are not regarded a pathologic signal for clinical use.

Fetal heart rate parameters and perinatal outcomes in fetuses with nuchal cords

AIM

The purpose of the present study was to compare and analyze differences in antepartal fetal heart rate (FHR) parameters during pregnancy and pregnancy outcomes in normal fetuses and fetuses with nuchal cord (NC).

MATERIAL AND METHODS

We surveyed all non-stress test (NST) data acquired using a computerized FHR analysis system at Hanyang University Hospital between 2005 and 2008, and selected 150 cases that had NC. NSTs were performed between 37 and 42 weeks of gestation. Subjects were divided into three groups by the number of NCs: no NC and normal (n = 300), single (n = 124) and multiple NCs (n = 26). Neonatal outcomes were compared, and FHR parameters analyzed using computerized fetal monitoring system.

RESULTS

FHR variability, with respect to amplitude (AMP) and mean minute range (MMR), was lower in the multiple NCs group than in the normal group (18.04 ± 0.38 vs 14.54 ± 1.10 bpm, P = 0.0207; 55.69 ± 1.22 vs 44.35 ± 3.41 ms, P = 0.0145, respectively). There were no other statistically significant differences of FHR parameters between the three groups. Baby weight was significantly lower in the multiple NCs group than in the normal group (3317 ± 24 vs 3054 ± 55; P = 0.0008), and there were no other significant differences between the groups.

CONCLUSION

Computerized analysis of FHR would be helpful to assess fetal status, especially in cases of multiple NCs. Multiple NCs may be a subliminal risk factor for the babies even though they present no complications at delivery.

Computerized fetal heart rate monitoring after vibroacoustic stimulation in the anencephalic fetus

BACKGROUND

To quantify changes in fetal heart rate (FHR) parameters after vibroacoustic stimulation (VAS) and to evaluate the usefulness of VAS testing (VAST) in anencephalic fetuses. Our findings may also help to clarify the route(s) of vibration and sound transmission during VAST.

STUDY DESIGN AND SUBJECTS

We obtained the antepartum FHR tracings of 16 anencephalic fetuses, including both the nonstress test (NST) and VAST. Using a computerized monitoring system, HYFM, we determined all FHR parameters from data collected for 10 min before and 10 min after VAS, at successive gestational stages.

RESULTS

We observed three false reactive responses at term. The false reactive rate for VAST (3/16) was higher than that for NST (1/16). No FHR parameters increased significantly after VAS except for the number of fetal movements (FM), which increased significantly in all gestational groups (25th-32nd and 33rd-40th weeks).

CONCLUSIONS

These findings call attention to an increased probability of a false reactive response in VAST analysis, when the fetus is affected by a CNS disorder. Increased numbers of FM after VAS suggest that the vibratory pathway is more likely to elicit fetal response than the auditory pathway in this setting, and that the vibratory stimulation travels by subcortical rather than by cortical pathways.

Computerized analysis of fetal heart rate in pregnancies complicated by gestational diabetes mellitus, gestational hypertension, intrauterine growth restriction and premature rupture of membranes

OBJECTIVE

We aimed to compare individual fetal heart rate (FHR) indices, as determined by computer analysis of the tracing, in pregnancies complicated by gestational diabetes mellitus (GDM), gestational hypertension (PIH), intrauterine growth restriction (IUGR) and premature rupture of membranes (pPROM).

METHODS

The study population consisted of 100 pregnant women affected by GDM on diet therapy, 100 pregnant women affected by GDM on insulin therapy, 100 pregnant women affected by PIH, 100 pregnant women affected by IUGR, 100 with premature rupture of membranes far from the term (pPROM) and 100 normal pregnancies matched for age, parity and gestation as controls. The 30-min FHR tracing was analyzed by computer.

RESULTS

Baseline FHR, the duration of episodes of low variation and short-term variation was significantly higher in pregnancies complicated by gestational diseases than in controls; only in PIH, IUGR and pPROM were a significant reduction of the numbers of fetal movements.

CONCLUSIONS

Our study demonstrates that pregnancies complicated by gestational diseases do an impact on FHR. The alteration is slight but evident; it reflects fetal well-being. Computerized FHR tracing analysis may improve the clinical care and the timing of delivery.

Determination of fetal heart rate reactivity from a single 20-min window of non-stress testing in compromised fetuses

AIMS

To shorten the analysis time needed for non-stress testing (NST) without decreasing efficacy in compromised fetuses.

METHODS

We selected 80 cases with a 5-min Apgar score <7 as a study group and 259 cases with a 5-min Apgar score >/=9 as a control group. We applied four different criteria (A, B, C, and D) to each study and control group for the first 20-min window of NST data to evaluate reactivity. Criteria A, B, and C consisted of conventional reactivity criteria according to amplitude (15 or 10 beats per minute), duration (15 or 10 s) and weeks of gestation (</=31, >/=32), and criteria D combined criteria C with approximate entropy (ApEn).

RESULTS

The sensitivity of criteria D (91.25%) was greater than the other three criteria (P<0.0001). The specificities of criteria C (96.14%) and D (99.23%) were also higher than criteria A and B (P<0.0001). The positive and negative predictive value of criteria D were better than that of criteria C (97.33 vs. 83.87, P=0.0066) and (97.35 vs. 89.89, P=0.0004), respectively.

CONCLUSION

Adding ApEn to the conventional criteria for reactivity shortened NST analysis time without decreasing efficacy, facilitating a decision of reactivity within a single 20-min NST window.

Computerized analysis of normal fetal heart rate pattern throughout gestation

OBJECTIVE

To analyze the evolution of computerized cardiotocography (cCTG) parameters throughout gestation in a large archive of traces from healthy fetuses.

METHODS

This was a cross-sectional study of the first cCTG record from 4412 singleton fetuses with good pregnancy outcome. Normal ranges of cCTG parameters for 25 to 42 weeks were derived from analysis of only one cCTG record per fetus, and the relationship between the parameters and gestational age was investigated.

RESULTS

Fetal heart rate (FHR) accelerations, short- and long-term variation overall, duration of episodes of high and low variation and variation in high episodes increased with advancing gestation. In contrast, maternal perception of fetal movements, basal FHR, variation in low episodes and the time until criteria for normality were met decreased with advancing gestation. Gestational age-related changes in FHR variation were less evident at the lowest percentiles. Episodes of high FHR variation were detected in most fetuses, even at 25 weeks. Opposite trends of basal FHR and variation were observed at 42 weeks. Large decelerations and the frequency and duration of low episodes were also higher at 42 weeks.

CONCLUSIONS

The characteristics of the normal FHR pattern are quite defined from early on in gestation, follow a continuous trend with advancing gestation and change abruptly at 42 weeks. Gestational age-related changes are less obvious at the lowest percentiles.

Fetal heart rate after vibroacoustic stimulation

OBJECTIVE

To define reference ranges for fetal heart rate (FHR) parameters after vibroacoustic stimulation (VAS) according to gestational age by determining the relationship between FHR and gestational age using a computerized analysis system.

METHODS

Data were analyzed from 3453 women using 10-minute observational recordings during nonstress testing (NST) and VAS testing. FHR parameters were analyzed according to gestational age.

RESULTS

All FHR parameters were related to gestational age except for mean baseline FHR, which did not vary significantly with gestational age. All other parameters followed trends similar to the NST results, except for decelerations.

CONCLUSION

FHR parameters after VAS differed significantly according to gestational age. The results suggest that the gestational age of the fetus should be considered when interpreting FHR patterns after VAS.

Changes in physiological and behavioural pain indicators over time in preterm and term infants at risk for neurologic impairment

BACKGROUND

Approximately 10% of infants admitted to a Neonatal Intensive Care Unit (NICU) are at risk for Neurological Impairment (NI). While we have limited knowledge on the influence of NI risk on pain responses, we have no knowledge of how these responses change over time.

OBJECTIVE

To compare physiological and behavioural pain responses of infants at three levels of NI risk during the NICU neonatal period (Session 1) and at 6 months of age (Session 2).

DESIGN/METHODS

Prospective observational design with 149 preterm and term infants at high (Cohort A, n=54), moderate (Cohort B, n=45) and mild (Cohort C, n=50) risks for NI from 3 Canadian tertiary level NICUs. Infants were observed in the NICU during 3 standardized phases of a heel lance: baseline, stick and return-to-baseline. At 6 months, infants were observed during the same three phases during an intramuscular immunization injection. Physiological (heart rate, oxygen saturation) and behavioural (9 facial actions, cry) responses were continuously recorded.

RESULTS

A significant interaction of Phase by Session was found with less total facial activity observed during Session 2 (all p values<0.04). A significant interaction for Session by Cohort was found, showing that infants in Cohort A had significantly more change from baseline-to-stick phase for brow bulge, eye squeeze, nasolabial furrow and open lips between sessions with less facial actions demonstrated at Session 2 (all p<0.02). There were significantly lower mean and minimum heart rate (all p<0.02) and higher minimum and maximum oxygen saturation (p<0.04) at Session 2. Significantly higher mean and minimum fundamental cry frequencies (pitch) in Cohort B (p<0.04) were found in Session 1. Cohort A had significantly longer cry durations, but no significant differences in cry dysphonation.

CONCLUSIONS

Behavioural and physiological infant pain responses were generally diminished at 6 months of age compared to those in the neonatal period with some differences between NI risk groups in cry responses. Future exploration into the explanation for these differences between sessions and cohorts is warranted.

Chaotic indices and canonical ensemble of heart rate patterns in small-for-gestational age fetuses

AIMS

We studied how linear and nonlinear heart rate dynamics differ between normal fetuses (n=135) and uncomplicated small-for-gestational age (SGA) fetuses (n=65), aged 32-40 weeks' gestation.

METHODS

We analyzed each fetal heart rate time series for 20 min. We quantified the complexity (nonlinear dynamics) of each fetal heart rate (FHR) time series by approximate entropy (ApEn) and correlation dimension (CD). The linear dynamics were analyzed by canonical correlation analysis (CCA).

RESULTS

The ApEn and CD of the uncomplicated SGA fetuses were significantly lower than that of the normal fetuses in all three gestational periods (32-34, 35-37, 38-40 weeks). Canonical correlation ensemble in SGA fetuses is slightly higher than normal ones in all three gestational periods, especially at 35-37 weeks.

CONCLUSIONS

Irregularity and complexity of the heart rate dynamics of SGA fetuses are lower than that of normal ones. Also, canonical ensemble in SGA fetuses is higher than in normal ones, suggesting that the FHR control system has multiple complex interactions. Along with the clear difference between the two groups' non-linear chaotic dynamics in FHR patterns, we clarified the hidden subtle differences in linearity (e.g., canonical ensemble). The decrease in non-linear dynamics may contribute to the increase in linear dynamics. The present statistical methodology can be readily and routinely utilized in obstetrics and gynecologic fields.

Intrapartum fetal monitoring today

The literature on intrapartum fetal monitoring is reviewed emphasizing the pathophysiology, and current practice guidelines are discussed. FHR monitoring, ancillary tests, and investigational modalities are considered.

Computerized analysis of the fetal heart rate in pregnancies complicated by preterm premature rupture of membranes (pPROM)

OBJECTIVE

We aimed to show that in pregnancies complicated by preterm premature rupture of membranes (pPROM), there are alterations to the fetal heart rate pattern that can be detected by computerized analysis.

METHODS

The study population consisted of 27 pregnant women with pPROM at 29-34 weeks of gestation and 33 normal pregnancies matched according to age, parity and gestation. A 30-minute fetal heart rate (FHR) tracing was analyzed by computer and umbilical artery cord blood was collected at birth.

RESULTS

The baseline heart rate, the number of decelerations exceeding 20 beats per minute and the duration of episodes of low variation were higher in the pPROM group versus the controls. The number of decelerations exceeding 20 beats per minute had an independent, statistically significant association with umbilical artery pH at birth.

CONCLUSIONS

Even if our data require a prospective validation involving a larger number of pathological cases, a computerized FHR tracing analysis may improve the clinical care and the timing of delivery during pPROM by definition of the risk of acidemia and pre-acidemia.