Fetal responses to vibratory acoustic stimulation: influence of basal heart rate

The effect of halogen light stimulation on duration of ultrasound parameters of biophysical profile: a randomized clinical trial

INTRODUCTION

The objective is to assess if fetal halogen light stimulation can reduce the time needed to obtain a normal biophysical profile (BPP).

METHODS

Patients scheduled for a BPP and who satisfied the inclusion criteria were prospectively randomized to halogen light stimulation and no stimulation groups. The study group was exposed to handheld halogen light for 10 s whenever fetal breathing, movement, or tone was absent through the first 5 min of BPP. The time required to achieve complete BPP score was recorded. In patients with complete BPP score who had delivery within 1 week after the test, perinatal morbidity was examined.

RESULTS

A total of 598 patients were randomized (light = 302, no light = 296). There was no difference between the two groups in terms of gestational age, maternal age, body mass index, and indication for BPP except for preterm labor (light: 9%, no light: 4%, p = 0.03). Among the patients who had a normal BPP score (n = 507), the mean (light: 7.1 ± 6 min, no light: 12.3 ± 8 min, p < 0.0001) and median (light: 4.3, no light: 8, p = 0.004) time needed to complete the BPP score was significantly less in the light stimulation group than the no stimulation group. Perinatal outcomes were not different between groups who had delivery during the first week after BPP.

CONCLUSION

Fetal halogen light stimulation can be utilized to reduce the time needed to complete a BPP. However, further studies should be conducted in order to determine the effect of this method on decreasing non-reassuring test results.

CLINICAL TRIAL REGISTRATION

The study was submitted to the Registry of Clinical Trials on 04/20/2017 (IRCT2017041633470N1). After IRCT registration on 06/07/2017, we recruited patients from 06/08/2017 till 10/15/2017.

Patterns of fetal heart rate response at ∼30 weeks gestation predict size at birth

There is evidence that fetal exposure to maternal stress is associated with adverse birth outcomes. Less is known about the association between fetal responses to a stressor and indicators of fetal maturity and developmental outcomes. The purpose of the present study was to determine whether fetal heart rate (FHR) patterns in response to a startling stimulus at ∼30 weeks of gestation were associated with gestational age at birth and birth weight. FHR was measured in 156 maternal-fetal dyads following a vibroacoustic stimulus. All pregnancies were singleton intrauterine pregnancies in English-speaking women who were primarily married, middle class, White and at least 18 years of age. Group-based trajectory modeling identified five groups of fetuses displaying distinctive longitudinal trajectories of FHR response to the startling stimulus. The FHR group trajectories were significantly associated with birth weight percentile (P < 0.01) even after controlling for estimated fetal weight at the time of assessment and parity, which are the known factors influencing birth weight (P < 0.01). Post hoc analyses indicated that two groups accounted for the association between FHR patterns and birth weight. The group (n = 23) with the lowest birth weight exhibited an immediate FHR deceleration followed by an immediate acceleration that does not recover. An FHR pattern characterized by immediate and fast acceleration to the peak and a slow discovery to baseline was associated with the highest birth weight. This is the first direct evidence showing that low birth weight and the resulting neurological consequences may have their origins in early fetal development.

Maturation of the human fetal startle response: evidence for sex-specific maturation of the human fetus

Despite the evidence for early fetal experience exerting programming influences on later neurological development and health risk, very few prospective studies of human fetal behavior have been reported. In a prospective longitudinal study, fetal nervous system maturation was serially assessed by monitoring fetal heart rate (FHR) responses to vibroacoustic stimulation (VAS) in 191 maternal/fetal dyads. Responses were not detected at 26 weeks gestational age (GA). Sex-specific, age-characteristic changes in the FHR response to VAS were observed by 31 weeks' GA. Males showed larger responses and continued to exhibit maturational changes until 37 weeks' GA, females however, presented with a mature FHR startle response by 31 weeks' GA. The results indicate that there are different rates of maturation in the male and female fetuses that may have implications for sex-specific programming influences.

The development of fetal hearing

The developmental origins of the ability to hear have been the subject of much debate and speculation. Since time immemorial, there has been much anecdotal evidence that the fetus responds to sound. In contrast, until the late 19th Century, scientific evidence and opinion held that the newborn was deaf and only developed the ability to hear in the first weeks after birth. At the beginning of the 20th Century the prevailing scientific and clinical view changed and it was accepted that the newborn was able to hear at birth. This led to much speculation about, and limited experimental study of, when the individual first started to hear. Detailed study of the ontogency of auditory abilities had to wait until the 1980’s when scientific opinion regarding the abilities of the newborn changed and the ultrasound technology with which to observe the fetus in utero became widely available. Research thus commenced in earnest to investigate the response of the fetus to sound. Despite this increased interest in fetal hearing, experimental studies have concentrated upon the responsiveness to sound in late pregnancy and not on the developmental origine of auditory abilities. It is the aim of this review to examine the ontogenesis of hearing in the fetus.

Vibroacoustic stimulation in abnormal biophysical profile: verification of facilitation of fetal well-being

OBJECTIVES

To verify the effect of vibroacoustic stimulation on biophysical profile score, with a prospective randomised study.

STUDY DESIGN

All women with singleton pregnancy, gestational age >or=30 weeks, intact membranes and biophysical profile score <or=8/10 entered the study, after giving written consent, and were randomised to two groups. In group A, a 3-s stimulus with an artificial larynx was applied; if biophysical profile remained abnormal for 30 min, a second stimulus was applied and it was assessed again. In group B, the observation time was extended for 60 min to match the time periods of group A. Pregnancies were managed by final test score and patients delivering more than 24 h apart from last examination were disregarded from the study. Outcome criteria were intrauterine deaths, caesarean sections for fetal distress, Apgar score <7 at 5 min postpartum, meconium-stained amniotic fluid and neonatal intensive care unit admissions. Our null hypothesis was that application of vibroacoustic stimulation does not alter test's statistical parameters.

RESULTS

1349 patients were randomised in group A and 1484 in group B (2833 in total). When comparing group A to B, application of vibroacoustic stimulation significantly decreased the number of positive tests (4.74% vs. 6.67%, p<0.05) and increased the prevalence of outcome criteria in this subgroup (positive likelihood ratio: 24.1 95% CI: 11.12-52.46 vs. 7.52 95% CI: 4.93-11.46), without altering perinatal outcome. Furthermore, specificity, positive predictive value and test accuracy were significantly improved, as well as negative predictive value for intrauterine death.

CONCLUSION

Vibroacoustic stimulation improves the efficiency of biophysical profile score by decreasing false positive tests and improving test accuracy and should be considered as a means of a more thorough fetal evaluation when fetal compromise is suspected.

Vibroacoustic and scalp stimulation

Both VAS and scalp stimulation are useful in the evaluation of fetal compromise by decreasing the number of falsely abnormal FHR tests and limiting the number of unnecessary interventions, thus improving the efficiency of antepartum and intrapartum FHR monitoring. As is true for all types of fetal assessment using FHR monitoring, VAS and scalp stimulation have limitations, and a lack of response to these methodologies does not necessarily indicate fetal acidemia. When either VAS or scalp stimulation is employed, one must take into consideration their respective predictive values (see Table 1). Fetal VAS or scalp stimulation should be considered as one facet of comprehensive fetal evaluation. When these techniques are used in this manner, the clinician evaluating the fetus in the antepartum or intrapartum period may prevent unnecessary intervention and improve maternal and neonatal outcome.

Nonstress testing and contraction stress testing

Antepartum fetal heart rate (FHR) testing, including the nonstress test and contraction stress test, has evolved in clinical usage over the past 3 decades. Although the nonstress test has become a standard of care in high-risk pregnancy, it has been modified by the use of fetal stimulation (vibroacoustic stimulation) and the addition of automated fetal movement recording (actocardiotocography). In all of its formats, antepartum FHR testing has been associated with reduction of preventable fetal loss. More recently, there have been attempts to improve test efficacy by computer-enhanced approaches.

Acoustic stimulation in hypoxic-ischemic encephalopathy: heart rate analysis

Two groups of 30 term newborns (normal and anoxic) were analyzed to study the influence of anoxia in the heart rate. The experiment consisted in a polygraphic EEG register before, during and after an acoustic stimulus. In basal conditions of active sleep, the heart rate in the asphyctic newborn was higher than in the normal group. The acoustic stimulation caused a transitional tachycardia. The variability of the heart rate was smaller in the asphyctic group. The basal heart rate varied in relation to the grade of Hypoxic-Ischemic Encephalopathy (HIE) and there was also a difference in the capacity of response to acoustic stimulation between the moderate HIE group and the normal group.

Evaluation of a simple method to assess fetal well-being in antenatal clinic

To study the feasibility of assessing fetal heart rate (FHR) acceleration by a fetal doptone and fetal movements (FM) as perceived by the mother and observed by the attendant in response to a vibroacoustic stimulus. Baseline FHR and it's response during the first minute after vibroacoustic stimulation was observed by a fetal doptone with a digital display on 317 occasions in 201 pregnancies (81.4% of whom were high risk) during antenatal visits in the third trimester. Fetal movements in response to the stimulus were recorded by the mother and the examiner. FHR increased 15 beats greater than the baseline rate for > 15 secs in 269 of the tests (83.4%), and fetal movements were observed by the mother in 301 (94.9%) of the tests. A FHR increase in > or = 15 bpm together with maternal and examiner perceived fetal movements were observed in 250 tests (81.7%). Good correlation was seen between the mother and the examiner (97.8%) of the observation of presence or absence of fetal movements to the vibroacoustic stimulus. One of the three parameters i.e. increase in FHR > or = 15 beats > or = 15 secs or perception of fetal movement either by the mother or the observer were present in 98.1% of the tests. If it could be considered that one of these three signs are indicative of good fetal health further investigations of fetal well-being would be needed in only 1.9%. The fetal outcome was uneventful in all pregnancies studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Computerised cardiotocography following vibro-acoustic stimulation

To study the effect of vibro-acoustic stimulation (VAS) to the mean fetal heart rate (FHR), period of high and low FHR variation, overall variation (msec and bpm) and short term variation (msec). In a prospective study 17 pregnant women between 34-42 weeks gestation admitted to antenatal ward for obstetric complications two 60 min FHR recording was carried out with an interval of 30 min in between recordings. On a random basis the fetus was stimulated by a vibro-acoustic stimulator for 5 sec at the beginning of one of the two 60 min FHR recordings. Automated analysis of the FHR, tocodynamometry, and maternal perception of fetal movements was done by a commercially available computerized programme (System 8000). It was possible to obtain the two 60 min recordings with signal loss of < 10% in 12 out of 17 patients. No changes were observed when the FHR parameters for 60 min after VAS was compared with the control period. When analyzed in segments of 0 to 10, 11 to 20, 20 to 40 and 41 to 60 min the mean baseline FHR was significantly higher after VAS during the first 10 minutes compared with any 10 or 20 min segment of the control period or any such segments 10 min after VAS. Concomitantly the overall variation and short-term variation was significantly lower during the first 10 minutes following VAS (p < 0.05) compared with the parameters in the corresponding periods during the control period.(ABSTRACT TRUNCATED AT 250 WORDS)

Vibro-acoustic stimulation does not alter the duration of high and low fetal heart rate variability episodes

To study the effect of vibro-acoustic stimulation on high and low fetal heart rate (FHR) variability episodes. Prospective control study, in 21 high risk pregnancies between 32 to 39 weeks gestation. FHR pattern was recorded with cardiotocograph (CTG). After 5 min low FHR variability a vibro-acoustic stimulator was activated in contact with or above the maternal abdomen (sham) on a random basis on two consecutive days, and CTG was continued to obtain a complete high and low FHR variability cycle. Complete high and low FHR variability cycles were obtained in 12 patients with mean recording time of 129.5 minutes (range 69-185 min). The mean baseline FHR increased by 32.5 +/- 9.4 bpm after contact vibro-acoustic stimulation, but remained unchanged after sham stimulation. Mean duration of high FHR variability was 56.6 +/- 32.9 min and 47.3 +/- 23.7 min, respectively, and mean duration of the consecutive low FHR variability episode was similar after contact and sham stimulation. The complete cycles were 71.1 +/- 34.7 min and 66.2 +/- 21.2 min, respectively. Vibro-acoustic stimulation induced an abrupt change from low to high FHR variability, but the complete cycle of high and low FHR variability was not altered, when compared with the corresponding cycle following sham stimulation on the same fetus.