1 The Journal of Maternal-Fetal and Neonatal Medicine, 2012; 1–4, Early Online Copyright © 2012 Informa UK, Ltd. ISSN 1476-7058 print/ISSN 1476-4954 online DOI: 10.3109/14767058.2011.648237 Objective: Preterm infants experience frequent cardiorespira- tory events (CREs) including multiple episodes of apnea and bradycardia per day. This physiological instability is due to their immature autonomic nervous system and limited capacity for self-regulation. This study examined whether systematic expo- sure to maternal sounds can reduce the frequency of CREs in NICU infants. Methods: Fourteen preterm infants (26–32 weeks gestation) served as their own controls as we measured the frequency of adverse CREs during exposure to either Maternal Sound Stimulation (MSS) or Routine Hospital Sounds (RHS). MSS consisted of maternal voice and heartbeat sounds recorded indi- vidually for each infant. MSS was provided four times per 24-h period via a micro audio system installed in the infant’s bed. Frequency of adverse CREs was determined based on monitor data and bedside documentation. Results: There was an overall decreasing trend in CREs with age. Lower frequency of CREs was observed during exposure to MSS versus RHS. This effect was significantly evident in infants ≥33 weeks gestation (p = 0.03), suggesting an effective therapeutic window for MSS when the infant’s auditory brain development is most intact. Conclusion: This study provides preliminary evidence for short-term improvements in the physiological stability of NICU infants using MSS. Future studies are needed to investigate the potential of this non-pharmacological approach and its clinical relevance to the treatment of apnea of prematurity. Keywords: Apnea of prematurity, maternal sounds, neonatal care Introduction Episodes of apnea in the preterm infant are thought to be secondary to physiologic immaturity of the autonomic nervous system and are oten associated with oxygen desaturation and/or bradycardia [1–4]. Associated episodes of apnea and bradycardia are oten collectively referred to as cardiorespiratory events (CREs [2,5,6]). he underlying mechanisms responsible for disturbances in cardiorespiratory regulation in the preterm infant are unclear. Histologically, the respiratory centers of the preterm brainstem are characterized by a decreased number of synaptic connec- tions and poor myelination [7]. In addition to these anatomical factors, the preterm brain is especially sensitive to inhibitory neurotransmitters [8]. When mild, CREs are not thought to have detrimental efects. However, more severe CREs have been shown to cause a decrease in cerebral blood low, putting the infant at risk of hypoxic-ischemic brain injury [9]. Due to this risk, the common medical impression is that preventing frequent CREs during NICU hospitalization is better for the long-term health of the infant. CREs can be treated pharmacologically with methylxanthines, most commonly cafeine, which act as central nervous system stimulants [10]. Although cafeine therapy is regarded as a safe and efective treatment of central apnea [1,3,4], it is not 100% efective in preventing CREs and can have adverse outcomes, such as mild tachycardia, vomiting, and restlessness [11]. Complete resolution of CREs requires maturation of central and peripheral responses to changes in arterial blood gas concentrations, a heightened ventilitory drive, and efective activation of upper airway muscles during respiration [8]. As these and other aspects of maturation progress with increasing gestational age, the incidence of apnea decreases [12]. Growing evidence suggests that postnatal cardiorespiratory regulation can be afected by environmental factors. Noise in particular, has been shown to impact cardiorespiratory regulation in newborns and to have greater efects on preterm infants with younger gestational age [13,14]. It is evident that low frequency maternal sounds, such as the mother’s voice and heartbeat, are audible inside the womb early in gestation [15]. Exposure to maternal sounds may therefore be crucial for healthy fetal development [16]. However, the speciic efects of maternal audi- tory stimulation on short-term physiological outcomes are still unclear. he purpose of this study was to examine the efects of biological maternal sounds on the cardiorespiratory stability of extremely preterm infants. We hypothesized that infants will have signiicantly less CREs during exposure to Maternal Sound Stimulation (MSS) than during exposure to Routine Hospital Sounds (RHS). Methods Patient population his study used a within-subject design paradigm to examine the exposure efects of MSS vs RHS on frequency of adverse CREs. Fourteen preterm infants admitted to the NICU at Brigham and Women’s Hospital participated in this study. Parents gave written ORIGINAL ARTICLE Exposure to biological maternal sounds improves cardiorespiratory regulation in extremely preterm infants Laura Doheny 1 , Shelley Hurwitz 2 , Robert Insoft 1 , Steven Ringer 1 & Amir Lahav 1,3 1 Department of Newborn Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA, 2 Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA, and 3 Department of Pediatrics, Mass General Hospital for Children, Boston, MA, USA Correspondence: Dr. Amir Lahav, ScD PhD, he Neonatal Research Lab, Department of Newborn Medicine, 75 Francis Street, Boston, Massachusetts 02115, USA. Tel: +1-617-732-5997. Fax: +1-617-278-6983. E-mail: amir@hms.harvard.edu (Received 01 August 2011; revised 22 November 2011; accepted 05 December 2011) J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Yale University on 02/08/12 For personal use only.