The impact of sound stimulations during pregnancy on fetal learning: a systematic review.

BACKGROUND: The developing nervous system in utero is exposed to various stimuli with effects that may be carried forward to the neonatal period. This study aims to investigate the effects of sound stimulation (music and speech) on fetal memory and learning, which was assessed later in neonatal period. METHODS: The MEDLINE (pubmed), Scopus, EMBASE, and Cochrane Library were searched. Two reviewers selected the studies and extracted the data independently. The quality of eligible studies was assessed using The Joanna Briggs Institute Critical Appraisal Checklist for Randomized Controlled Trials (RCTs). RESULTS: Overall 3930 articles were retrieved and eight studies met the inclusion criteria. All of the included studies had good general quality; however, high risk of selection and detection bias was detected in most of them. Fetal learning was examined through neonatal electrocardiography (ECG), electroencephalography (EEG), habituation tests, and behavioral responses. Seven studies showed that the infants had learned the fetal sound stimulus and one study indicated that the prenatally stimulated infants performed significantly better on a neonatal behavior test. There was considerable diversity among studies in terms of sound stimulation type, characteristics (intensity and frequency), and duration, as well as outcome assessment methods. CONCLUSIONS: Prenatal sound stimulation including music and speech can form stimulus-specific memory traces during fetal period and effect neonatal neural system. Further studies with precisely designed methodologies that follow safety recommendations, are needed.

Neonatal responsiveness to the odor of amniotic fluid / Respuesta neonatal frente al olor del líquido amniótico

This study evaluated the neonatal responsiveness to the odor of amniotic fluid during the first hours of life. Twenty five newborn infants born by C-section at 36-40 weeks of gestation were evaluated with 1; 5 or 25 drops of amniotic fluid at 1 hour, 3.5 hours and 6 hours of life. A five stimuli habituation plan was used and global motor activity was recorded. Mixed-design ANOVAs for repeated measures demonstrated time differences and showed the highest reactivity at 1 hour, a reduction at 3.5 hours and a recovery at 6 hours (p < 0.0000). Maximum response was observed at the beginning, with a subsequent reduction (p < 0.0088). T tests were used to compare mean differences from baseline to the stimulation period. It was observed that one drop was enough to trigger a response, even at 6 hours of life (p = 0.045). Apparently, babies are able to detect minimum amounts of amniotic fluid and habituate the response with repeated exposure during their first hours of life.(AU)

En este trabajo se evaluó la respuesta neonatal al olor del líquido amniótico durante las primeras horas de vida. Veinticinco recién nacidos por cesárea entre las 36 y 40 semanas gestacionales fueron evaluados con 1; 5 o 25 gotas a la hora, a las tres horas y media, y a las seis horas de vida. Se utilizó un esquema habituacional de cinco estímulos y se registró la actividad motora global. Los ANOVA mixtos para medidas repetidas reflejaron las diferencias en los tiempos y mostraron la mayor reactividad en la primera hora, la disminución de ésta a las tres horas y media, y la recuperación a la sexta hora (p <0,0000). La máxima respuesta se observaba al comienzo y luego disminuía (p <0,0088). Con las pruebas T se compararon las medias entre el basal previo y el período de estimulación. Pudo observarse que una gota era suficiente para generar una respuesta, aun a la sexta hora de vida (p = 0,045). Aparentemente, durante las primeras horas los bebés pueden detectar mínimas cantidades de líquido amniótico y habitúan su respuesta con la exposición repetida.(AU)

Neonatal responsiveness to the odor of amniotic fluid / Respuesta neonatal frente al olor del líquido amniótico

This study evaluated the neonatal responsiveness to the odor of amniotic fluid during the first hours of life. Twenty five newborn infants born by C-section at 36-40 weeks of gestation were evaluated with 1; 5 or 25 drops of amniotic fluid at 1 hour, 3.5 hours and 6 hours of life. A five stimuli habituation plan was used and global motor activity was recorded. Mixed-design ANOVAs for repeated measures demonstrated time differences and showed the highest reactivity at 1 hour, a reduction at 3.5 hours and a recovery at 6 hours (p < 0.0000). Maximum response was observed at the beginning, with a subsequent reduction (p < 0.0088). T tests were used to compare mean differences from baseline to the stimulation period. It was observed that one drop was enough to trigger a response, even at 6 hours of life (p = 0.045). Apparently, babies are able to detect minimum amounts of amniotic fluid and habituate the response with repeated exposure during their first hours of life.

En este trabajo se evaluó la respuesta neonatal al olor del líquido amniótico durante las primeras horas de vida. Veinticinco recién nacidos por cesárea entre las 36 y 40 semanas gestacionales fueron evaluados con 1; 5 o 25 gotas a la hora, a las tres horas y media, y a las seis horas de vida. Se utilizó un esquema habituacional de cinco estímulos y se registró la actividad motora global. Los ANOVA mixtos para medidas repetidas reflejaron las diferencias en los tiempos y mostraron la mayor reactividad en la primera hora, la disminución de ésta a las tres horas y media, y la recuperación a la sexta hora (p <0,0000). La máxima respuesta se observaba al comienzo y luego disminuía (p <0,0088). Con las pruebas T se compararon las medias entre el basal previo y el período de estimulación. Pudo observarse que una gota era suficiente para generar una respuesta, aun a la sexta hora de vida (p = 0,045). Aparentemente, durante las primeras horas los bebés pueden detectar mínimas cantidades de líquido amniótico y habitúan su respuesta con la exposición repetida.