Sex differences in prenatal oral-motor function and development

Lung ultrasound supports clinical evaluation of feeding competence development in preterm neonates

Introduction

The achievement of alimentary competencies is a milestone in the development of preterm neonates. Ten percent of neonates <37 weeks of gestational age and 25% of those VLBW experience swallowing disorders, with an increased risk of problems in the early phase of life (failure to thrive, growth retardation, inhalation, and consequent risk of pulmonary infection) and later in life due to delayed development of oromotor skills.The main diagnostic tools for swallowing disorders are endoscopic (fiber-optic endoscopic examination of swallowing, FEES) or radiographic (videofluoroscopic swallowing study, VFSS) exams. Given the invasiveness of these methods and the bias due to rheologic differences between bolus and contrast medium, FEES and VFSS are poorly reproducible. Moreover, neither of the technique is capable of detecting post-meal inhalations, especially microinhalations or those consequent to a whole meal rather than to a single swallowing.Lung ultrasound (LUS) is a widespread, repeatable, safe, fast point-of-care tool and we reported previous encouraging results in detecting silent and overt inhalation related to the meal in children with dysphagia/gastroesophageal reflux disease (GERD) risk factors.

Methods

We report a pilot study, that investigated LUS approach (performing imaging before and after meals) to assess feeding competence development in a cohort of n. 19 newborns <32 weeks of age.

Results

Meal monitoring by LUS did not show any significant difference in scoring before/after eating. The achievement of full enteral feeding correlates with GA at birth (p < 0.001) but not with LUS scoring. The introduction of the first meal by bottle correlates both with gestational age (p < 0.001) and ultrasound scores (p = 0.004). LUS score at 7 days of life resulted predictive for length of invasive/non-invasive respiratory support (p = 0.002) and length of oxygen supply (p = 0.001), while LUS score at 48 h of life did not (p n.s.).

Discussion

Our study suggests that the development of oral feeding skills is not strictly dependent on gestational age. Moreover, our research suggests the predominant role of LUS in predicting the time of readiness to oral feeding, as the LUS score can be a marker of respiratory and lung wellness, and consequently a predictor of neonate stability during deglutitory apnea.

Neural Indices of Vowel Discrimination in Monolingual and Bilingual Infants and Children

OBJECTIVES

To examine maturation of neural discriminative responses to an English vowel contrast from infancy to 4 years of age and to determine how biological factors (age and sex) and an experiential factor (amount of Spanish versus English input) modulate neural discrimination of speech.

DESIGN

Event-related potential (ERP) mismatch responses (MMRs) were used as indices of discrimination of the American English vowels [ε] versus [I] in infants and children between 3 months and 47 months of age. A total of 168 longitudinal and cross-sectional data sets were collected from 98 children (Bilingual Spanish-English: 47 male and 31 female sessions; Monolingual English: 48 male and 42 female sessions). Language exposure and other language measures were collected. ERP responses were examined in an early time window (160 to 360 msec, early MMR [eMMR]) and late time window (400 to 600 msec, late MMR).

RESULTS

The eMMR became more negative with increasing age. Language experience and sex also influenced the amplitude of the eMMR. Specifically, bilingual children, especially bilingual females, showed more negative eMMR compared with monolingual children and with males. However, the subset of bilingual children with more exposure to English than Spanish compared with those with more exposure to Spanish than English (as reported by caretakers) showed similar amplitude of the eMMR to their monolingual peers. Age was the only factor that influenced the amplitude of the late MMR. More negative late MMR was observed in older children with no difference found between bilingual and monolingual groups.

CONCLUSIONS

Consistent with previous studies, our findings revealed that biological factors (age and sex) and language experience modulated the amplitude of the eMMR in young children. The early negative MMR is likely to be the mismatch negativity found in older children and adults. In contrast, the late MMR amplitude was influenced only by age and may be equivalent to the Nc in infants and to the late negativity observed in some auditory passive oddball designs.

Transcutaneous Auricular Vagus Nerve Stimulation-Paired Rehabilitation for Oromotor Feeding Problems in Newborns: An Open-Label Pilot Study

Neonates born premature or who suffer brain injury at birth often have oral feeding dysfunction and do not meet oral intake requirements needed for discharge. Low oral intake volumes result in extended stays in the hospital (>2 months) and can lead to surgical implant and explant of a gastrostomy tube (G-tube). Prior work suggests pairing vagus nerve stimulation (VNS) with motor activity accelerates functional improvements after stroke, and transcutaneous auricular VNS (taVNS) has emerged as promising noninvasive form of VNS. Pairing taVNS with bottle-feeding rehabilitation may improve oromotor coordination and lead to improved oral intake volumes, ultimately avoiding the need for G-tube placement. We investigated whether taVNS paired with oromotor rehabilitation is tolerable and safe and facilitates motor learning in infants who have failed oral feeding. We enrolled 14 infants [11 premature and 3 hypoxic-ischemic encephalopathy (HIE)] who were slated for G-tube placement in a prospective, open-label study of taVNS-paired rehabilitation to increase feeding volumes. Once-daily taVNS was delivered to the left tragus during bottle feeding for 2 weeks, with optional extension. The primary outcome was attainment of oral feeding volumes and weight gain adequate for discharge without G-tube while also monitoring discomfort and heart rate (HR) as safety outcomes. We observed no adverse events related to stimulation, and stimulation-induced HR reductions were transient and safe and likely confirmed vagal engagement. Eight of 14 participants (57%) achieved adequate feeding volumes for discharge without G-tube (mean treatment length: 16 ± 6 days). We observed significant increases in feeding volume trajectories in responders compared with pre-stimulation (p < 0.05). taVNS-paired feeding rehabilitation appears safe and may improve oral feeding in infants with oromotor dyscoordination, increasing the rate of discharge without G-tube, warranting larger controlled trials.

Investigating Tongue Strength and Endurance in Children Aged 6 to 11 Years

Objective measures of tongue strength and endurance are used to assess lingual weakness and fatigue, and may have significant clinical value for dysphagia management. Recent studies investigating age and gender effects on tongue strength in children are limited by small sample sizes. The current study investigated age and gender effects on tongue strength with a larger sample size, and collected preliminary normative data for a paediatric population. This study also investigated the reliability of tongue endurance measures in children using a modified method, which has not previously been investigated. Using a cross-sectional design, this study examined tongue strength and endurance in 119 children aged 6 to 11 years, with no history of speech sound disorders, oro-motor deficits, dysphagia or cognitive impairment. Measures were collected using the Iowa Oral Performance Instrument. Children participated in two sessions, 45 min and 10 min in duration. Tongue strength was found to significantly increase with age (p < 0.001), while no gender effects were found. Modified tongue endurance measures involved using only one measure of maximal tongue strength to set parameters for tongue endurance scores. Despite this modification, data did not reach acceptable test-retest reliability, ICC = 0.68, p < 0.001; however, reliability improved from previous studies. These findings provide normative data for tongue strength, as a basis to compare individuals, and highlights the need for more reliable protocols for measuring tongue endurance. Normative data was collected from city-dwelling Australian children.

Assessment of autonomic function in the late term fetus: The effects of sex and state

Researchers have reported associations between fetal sex and heart rate (FHR) and heart rate variability (FHRV) but rarely in the context of fetal behavioral sleep state. We examined differences in measures of fetal autonomic function by sex and sleep state. Fetal abdominal ECG monitoring technology was used to measure FHR and two measures of FHRV-standard deviation of FHR (SD) and beat-to-beat variability (RMSSD). FHR and movement patterns were also recorded with standard Doppler ultrasound monitor technology employed to code sleep states. Data were collected from 82 healthy fetuses ranging from 36 to 39 weeks gestation. A one-way MANOVA showed that FHR was significantly lower and SD was significantly higher for males than females. Independent samples t tests found that these sex differences were only in the active sleep state. There were no significant differences in RMSSD by sex. Repeated measures MANOVA for a subset that exhibited more than one state (N = 22) showed that SD was significantly different by state. RMSSD showed a marginally significant sleep state difference. In conclusion, fetal sex differences in HR and HRV may indicate more mature autonomic functioning in near-term males than females and fetal sleep state can influence abdominal fECG derived measures of FHR and FHRV.

A key developmental step for preterm babies: achievement of full oral feeding

Aims: To investigate timing of oral feeding (OF) introduction and full oral feeding (FOF) achievement in preterm infants and to explore factors associated with feeding progression.Methods: Retrospective review of 100 medical records of preterms ≤32 weeks of gestation (GA) without major complications. Outcome measures were timing of OF introduction, transition time from nasogastric tube to FOF and FOF achievement. Variables such as sex, twins, GA, birthweight, respiratory supports used and duration of tube feeding, were also considered.Results: Post menstrual age (PMA) for OF introduction was 33.6 ± 1.1 weeks. FOF was achieved at 35.1 ± 1.5 weeks. PMA at OF introduction and PMA at FOF correlated with: birthweight (p = .0001, p = .001); duration of respiratory supports (p = 0.01, p = .0001); PMA at which respiratory supports were stopped (p = .0001, p = .0001); age of introduction of gavage (p = .0001, p = .003) and time of utilization of tube feeding (p = .02, p = .0001). Transition time was 1.5 ± 8.5 days. PMA at OF introduction significantly influenced PMA at FOF (p = .0001, r = .61). OF introduction, transition time and FOF were correlated with duration of hospitalization (p = .004, p = .0001, p = .008).Conclusions: The achievement of feeding skills is confirmed to affect length of hospitalization, but the earlier you introduce OF, the earlier you reach FOF, so introduction should be anticipated. There is a clear trend to favor higher birthweight classes in FOF achievement. Feeding tube placement and need for respiratory supports may represent a nociceptive experience delaying feeding skills' achievement. This highlights the importance of prospective studies investigating the role of preventative interventions.

Aspiration and Dysphagia in the Neonatal Patient

Dysphagia and aspiration are commonly encountered problems in the neonatal population. It is often multifactorial in nature and management should be tailored to the individual patient. Multiple causes should be considered, including anatomic abnormalities, neurologic/developmental delay, cardiopulmonary disease/infection, and gastroesophageal reflux disease, in addition to those cases where a definitive reason may not be identified. Management should be multidisciplinary in nature and surgical intervention may be indicated in certain populations of patients. Here, we discuss the presentation, workup, and management of the neonatal patient with dysphagia and aspiration.

Dissociations among linguistic, cognitive, and auditory-motor neuroanatomical domains in children who stutter

The onset of developmental stuttering typically occurs between 2 to 4 years of age, coinciding with a period of rapid development in speech, language, motor and cognitive domains. Previous studies have reported generally poorer performance and uneven, or "dissociated" development across speech and language domains in children who stutter (CWS) relative to children who do not stutter (CWNS) (Anderson, Pellowski, & Conture, 2005). The aim of this study was to replicate and expand previous findings by examining whether CWS exhibit dissociated development across speech-language, cognitive, and motor domains that are also reflected in measures of neuroanatomical development. Participants were 66CWS (23 females) and 53CWNS (26 females) ranging from 3 to 10 years. Standardized speech, language, cognitive, and motor skills measures, and fractional anisotropy (FA) values derived from diffusion tensor imaging from speech relevant "dorsal auditory" left perisylvian areas (Hickok & Poeppel, 2007) were analyzed using a correlation-based statistical procedure (Coulter, Anderson, & Conture, 2009) that quantified dissociations across domains. Overall, CWS scored consistently lower on speech, language, cognitive and motor measures, and exhibited dissociated development involving these same measures and white matter neuroanatomical indices relative to CWNS. Boys who stutter exhibited a greater number of dissociations compared to girls who stutter. Results suggest a subgroup of CWS may have incongruent development across multiple domains, and the resolution of this imbalance may be a factor in recovery from stuttering.

Predictors of the time to attain full oral feeding in late preterm infants

AIM

The aim of this study was to determine the factors that predict the timing and age at which preterm infants (born 32-36 weeks gestation) commenced and attained full oral feeding.

METHODS

We conducted a retrospective review of medical records of 647 preterm infants born 2005-2011. Infants were from six neonatal intensive care units in New Zealand, all World Health Organisation Baby-friendly Hospital Initiative accredited.

RESULTS

Median time to the first oral feed offered was one day, and median time to the time of full oral feeding was 12 days. No infants attained full oral feeding before 33(+3) weeks postmenstrual age. Gestational age, birthweight, medical conditions and location of the neonatal unit were significantly associated with the time taken to commence and attain full oral feeding.

CONCLUSION

This study highlights the factors that are associated with the rate at which late preterm infants commence oral feeding and progress to full oral feeding. These findings offer important considerations not only for clinical practice but also discharge planning given the preference for preterm infants reaching full oral feeds before discharge from hospital. Prospective experimental research is required to confirm infant, maternal and environmental factors that influence feeding milestones in late preterm infants.

STUDIES IN FETAL BEHAVIOR: REVISITED, RENEWED, AND REIMAGINED

Among the earliest volumes of this monograph series was a report by Lester Sontag and colleagues, of the esteemed Fels Institute, on the heart rate of the human fetus as an expression of the developing nervous system. Here, some 75 years later, we commemorate this work and provide historical and contemporary context on knowledge regarding fetal development, as well as results from our own research. These are based on synchronized monitoring of maternal and fetal parameters assessed between 24 and 36 weeks gestation on 740 maternal-fetal pairs compiled from eight separate longitudinal studies, which commenced in the early 1990s. Data include maternal heart rate, respiratory sinus arrhythmia, and electrodrmal activity and fetal heartrate, motor activity, and their integration. Hierarchical linear modeling of developmental trajectories reveals that the fetus develops in predictable ways consistent with advancing parasympathetic regulation. Findings also include:within-fetus stability (i.e., preservation of rank ordering over time) for heart rate, motor, and coupling measures; a transitional period of decelerating development near 30 weeks gestation; sex differences in fetal heart rate measures but not in most fetal motor activity measures; modest correspondence in fetal neurodevelopment among siblings as compared to unrelated fetuses; and deviations from normative fetal development in fetuses affected by intrauterine growth restriction and other conditions. Maternal parameters also change during this period of gestation and there is evidence that fetal sex and individual variation in fetal neurobehavior influence maternal physio-logical processes and the local intrauterine context. Results are discussed within the framework of neuromaturation, the emergence of individual differences, and the bidirectional nature of the maternal-fetal relationship.We pose a number of open questions for future research. Although the human fetus remains just out of reach, new technologies portend an era of accelerated discovery of the earliest period of development

The gestational foundation of sex differences in development and vulnerability

Despite long-standing interest in the role of sex on human development, the functional consequences of fetal sex on early development are not well-understood. Here we explore the gestational origins of sex as a moderator of development. In accordance with the focus of this special issue, we examine evidence for a sex differential in vulnerability to prenatal and perinatal risks. Exposures evaluated include those present in the external environment (e.g., lead, pesticides), those introduced by maternal behaviors (e.g., alcohol, opioid use), and those resulting from an adverse intrauterine environment (e.g., preterm birth). We also provide current knowledge on the degree to which sex differences in fetal neurobehavioral development (i.e., cardiac and motor patterns) are present prior to birth. Also considered are contemporaneous and persistent sex of fetus effects on the pregnant woman. Converging evidence confirms that infant and early childhood developmental outcomes of male fetuses exposed to prenatal and perinatal adversities are more highly impaired than those of female fetuses. In certain circumstances, male fetuses are both more frequently exposed to early adversities and more affected by them when exposed than are female fetuses. The mechanisms through which biological sex imparts vulnerability or protection on the developing nervous system are largely unknown. We consider models that implicate variation in maturation, placental functioning, and the neuroendocrine milieu as potential contributors. Many studies use sex as a control variable, some analyze and report main effects for sex, but those that report interaction terms for sex are scarce. As a result, the true scope of sex differences in vulnerability is unknown.

Can healthy fetuses show facial expressions of "pain" or "distress"?

BACKGROUND

With advances of research on fetal behavioural development, the question of whether we can identify fetal facial expressions and determine their developmental progression, takes on greater importance. In this study we investigate longitudinally the increasing complexity of combinations of facial movements from 24 to 36 weeks gestation in a sample of healthy fetuses using frame-by-frame coding of 4-D ultrasound scans. The primary aim was to examine whether these complex facial movements coalesce into a recognisable facial expression of pain/distress.

METHODOLOGY/FINDINGS

Fifteen fetuses (8 girls, 7 boys) were observed four times in the second and third trimester of pregnancy. Fetuses showed significant progress towards more complex facial expressions as gestational age increased. Statistical analysis of the facial movements making up a specific facial configuration namely "pain/distress" also demonstrates that this facial expression becomes significantly more complete as the fetus matures.

CONCLUSIONS/SIGNIFICANCE

The study shows that one can determine the normal progression of fetal facial movements. Furthermore, our results suggest that healthy fetuses progress towards an increasingly complete pain/distress expression as they mature. We argue that this is an adaptive process which is beneficial to the fetus postnatally and has the potential to identify normal versus abnormal developmental pathways.

Neonatal factors associated with alteration of palatal morphology in very preterm children: the EPIPAGE cohort study

BACKGROUND

Altered palatal morphology has been observed among some preterm children, with possible consequences on chewing, speaking and esthetics, but determinants remain unknown.

AIM

To explore the role of neonatal characteristics and neuromotor dysfunction in alteration of palatal morphology at 5 years of age in very preterm children.

STUDY DESIGN

Prospective population-based cohort study.

SUBJECTS

1711 children born between 22 and 32 weeks of gestation in 1997 or born between 22 and 26 weeks of gestation in 1998 were included in the study. They all had a medical examination at 5 years of age.

OUTCOME MEASURES

Alteration of palatal morphology.

RESULTS

The prevalence of altered palatal morphology was 3.7% in the overall sample, 5.1% among boys and 2.2% among girls (adj OR: 2.52; 95%CI: 1.44-4.42). The risk for altered palatal morphology was higher for lower gestational age (adj OR: 0.85; 95%CI: 0.74-0.97 per week), small-for-gestational age children (adj OR: 2.11; 95%CI: 1.20-3.72) or children intubated for more than 28 days (adj OR: 3.16; 95%CI: 1.11-8.98). Altered palatal morphology was more common in case of cerebral palsy or moderate neuromotor dysfunction assessed at 5 years. Results were basically the same when neuromotor dysfunction was taken into account, except for intubation.

CONCLUSION

Male sex, low gestational age, small-for-gestational age and long intubation have been identified as probable neonatal risk factors for alteration of palatal morphology at 5 years of age in very preterm children. Further studies are needed to confirm these results.

Sexual dimorphism of the human mandible and its association with dental development

The present study investigates whether the human mandible is sexually dimorphic during early postnatal development and whether early dimorphic features persist during subsequent ontogeny. We also examine whether mandibular dimorphism is linked to dimorphism of dental development. Dense CT-derived mandibular meshes of 84 females and 75 males, ranging from birth to adulthood, were analyzed using geometric morphometric methods. On the basis of the specimen's chronological ages and mineralization stages of the deciduous and permanent teeth, we compute dental age as proxy for dental development by the additive conjoint measurement method. By birth, males have, on average, more advanced age-specific shapes than females. However, sex differences decrease quickly as females catch up via a different association between shape and size. This leads to an almost complete reduction of sexual dimorphism between the ages of 4 and 14. From puberty to adulthood, males are characterized by allometric shape changes while the shape of the female mandible continues to change even after size has ceased to increase. Dimorphism of dental maturation becomes visible only at puberty. Sexual dimorphism, concentrated at the ramus and the mental region during the earliest ontogenetic stages and again at adulthood, is not associated with the development of the teeth. At puberty there is a simultaneous peak in size increase, shape development, and dental maturation likely controlled by the surge of sex hormones with a dimorphic onset age. We argue that the infant and adult dimorphism of the mental region may be associated with the development of supralaryngeal structures.

Sonographically measured hyoid bone displacement during swallow in preschool children: a preliminary study

PURPOSE

This study explored normative parameters regarding maximum displacement of hyoid bone movement during spontaneous swallows using ultrasound (US) in a sample of healthy preschool children. We hypothesized that consistency and bolus size would influence hyoid movement, but gender would not be a factor.

METHODS

Parental questionnaire responses and sensorimotor examinations were utilized to determine subject eligibility. Subjects were presented randomized bolus volumes of thin liquids/puree via a spoon while the US probe was placed submentally in the midsagittal plane. Maximum hyoid bone displacement was determined following a frame-by-frame analysis of the US recording during spontaneous swallowing of discrete bolus sizes.

RESULTS

Twenty-nine subjects produced 346 swallows that were subsequently analyzed. Significant findings (p < 0.05) included a gender effect with the smallest bolus of liquids presented. Bootstrap estimates based on our sample revealed that 99% of preschool children would present with hyoid bone displacement within 0.3 cm of our sample.

CONCLUSIONS

Based on our early experience, we were able to observe and measure changes in hyoid bone position during swallowing in preschoolers, which may be gender related. More studies are needed to corroborate our findings. In addition, comparisons of maximum hyoid displacement are warranted in subjects that present with feeding delays.

Neonatal neurobehavioral organization after exposure to maternal epidural analgesia in labor

OBJECTIVE

To explore relationships between maternal epidural analgesia and two measures of neurobehavioral organization in infants at the initial feeding 1 hour after birth.

DESIGN

Prospective comparative design.

SETTING

Inner-city community hospital, Chicago, Illinois.

PARTICIPANTS

Convenience sample of 52 low-risk, mainly Black and Latino, mother/infant dyads.

METHODS

Mothers self-selected to labor with epidural or no labor pain medication. Neonatal neurobehavioral organization was measured in term infants at the initial feeding 1 hour after birth. A nutritive sucking apparatus generated data on total number of sucks and sucking pressure. Video recordings of infants (before and after the initial feeding) were coded for behavioral states, with analysis on frequency of alertness.

RESULTS

Total number of sucks and sucking pressure were not related to epidural exposure, although an epidural drug dosage effect on total number of sucks was evident when gender was a factor. Unmedicated girls demonstrated more sucks than girls in the high-dosage epidural group (p=.027). Overall, girls exhibited stronger sucking pressure than boys (p=.042). Frequency of alertness was not related to epidural exposure, although longer labor was related to greater alertness (p=.003), and Latino infants were more alert than Black infants (p=.002).

CONCLUSIONS

Results suggest attenuated neonatal nutritive sucking organization in girls after exposure to high maternal epidural dosages. In comparison to boys, girls may have enhanced neurobehavioral organization at birth. Race/ethnicity and alertness may have spurious associations in which hidden factors drive the relationship.

A socio-relational framework of sex differences in the expression of emotion

Despite a staggering body of research demonstrating sex differences in expressed emotion, very few theoretical models (evolutionary or non-evolutionary) offer a critical examination of the adaptive nature of such differences. From the perspective of a socio-relational framework, emotive behaviors evolved to promote the attraction and aversion of different types of relationships by advertising the two most parsimonious properties of reciprocity potential, or perceived attractiveness as a prospective social partner. These are the individual's (a) perceived capacity or ability to provide expedient resources, or to inflict immediate harm onto others, and their (b) perceived trustworthiness or probability of actually reciprocating altruism (Vigil 2007). Depending on the unique social demands and relational constraints that each sex evolved, individuals should be sensitive to advertise "capacity" and "trustworthiness" cues through selective displays of dominant versus submissive and masculine versus feminine emotive behaviors, respectively. In this article, I introduce the basic theoretical assumptions and hypotheses of the framework, and show how the models provide a solid scaffold with which to begin to interpret common sex differences in the emotional development literature. I conclude by describing how the framework can be used to predict condition-based and situation-based variation in affect and other forms of expressive behaviors.

Preliminary Ultrasound Observation of Lingual Movement Patterns During Nutritive versus Non-nutritive Sucking in a Premature Infant

Term neonates must suck, swallow, and respire in a coordinated manner during successful oral feeding. When infants are born prematurely, these skills may not be fully mature. To stimulate sucking responses, premature infants are offered pacifiers under the premise that non-nutritive sucking experiences facilitate oral feeding readiness. This case reported examined the lingual-hyoid mechanics of non-nutritive suck (NNS) patterns with a pacifier versus nutritive suck (NS) during a bottle feed in a premature infant using a noninvasive ultrasound imaging technique as a pilot to discern aspects of oral feeding candidacy. Lingual patterns during NS resulted in significantly greater displacements and excursions than NNS (p < 0.0001) in both anterior and posterior regions of the tongue (p < 0.0001). In addition, the angle of hyoid movement during NNS was significantly smaller (p < 0.05) than the angle recorded during NS tasks. Unlike an expected neonatal sucking pattern of horizontal anterior-posterior movements of the tongue body, vertical tongue body excursions occurred as described in the literature of representing a 6-9-month developmental skill level. Through the integration of semiautomatic computerized analyses of tongue surface configurations and hyoid activity, these data may enhance knowledge of oral swallowing function in developing preterm neonates.