Activity-based assessment of the sleep behaviors of VLBW preterm infants and full-term infants at around 12 months of age

Purpose: The aim of this study is to identify the characteristics of sleep behaviors assessed from activity data among very low-birth weight (VLBW) preterm infants in comparison to full-term infants at the age of around 12 corrected months, due to the possibility that sleep behaviors of preterm infants may be different from those of full-term infants. Method: Cross-sectional study. Infant sleep measures were obtained through actigraphs (Micro-mini RC, Ambulatory Monitoring Inc., Ardsley, NY), which were attached to the infants’ ankles during a week-long period. The subjects were 14 preterm infants and 14 full-term infants in which the mean ages were 13.3 ± 2.1 corrected months and 12.3 ± 2.4 month, respectively. Results: Preterm infants showed significantly less sleep duration during nighttime than full-term infants. The mean activity score and ACTX (Activity Index: percentage minutes with more than 0 activity score) of preterm infants during nighttime were significantly higher than those of full-term infants. No significant differences in total sleep duration, daytime sleep duration, the number of night-wakings, and sleep efficiency were found between the two groups. Conclusion: Preterm infants slept less and had a larger percentage of less restful sleep during nighttime. The results indicated that prematurity at the time of birth remained throughout the developmental course of sleep behaviors among preterm infants at around the age of 12 corrected months.     

Early vocalization of preterm infants with extremely low birth weight (ELBW), part II: from canonical babbling up to the appearance of the first word

The aim of this study was to systematically describe the preverbal development of preterm infants from canonical babbling up to the first word and to compare it with that of healthy full-term infants. In addition, the amount of vocalization between the preterm and full-term groups was compared. The sample consisted of 18 preterm infants with extremely low birth weight and 11 full-term infants. The development of preverbal vocalization before variegated babbling did not differ between the groups. Instead, the preterm infants failed to produce more different kinds of canonical syllable types than the full-term infants. However, they showed a larger variance of variegated babbling skills and remained in the babbling phase longer before reaching the first meaningful word compared with the full-term infants. Following the onset of canonical babbling, the preterm infants produced fewer vocalizations than the full-term infants and they reached the first word later than the full-term infants.     

Early vocalization of preterm infants with extremely low birth weight (ELBW), Part II: From canonical babbling up to the appearance of the first word

The aim of this study was to systematically describe the preverbal development of preterm infants from canonical babbling up to the first word and to compare it with that of healthy full-term infants. In addition, the amount of vocalization between the preterm and full-term groups was compared. The sample consisted of 18 preterm infants with extremely low birth weight and 11 full-term infants. The development of preverbal vocalization before variegated babbling did not differ between the groups. Instead, the preterm infants failed to produce more different kinds of canonical syllable types than the full-term infants. However, they showed a larger variance of variegated babbling skills and remained in the babbling phase longer before reaching the first meaningful word compared with the full-term infants. Following the onset of canonical babbling, the preterm infants produced fewer vocalizations than the full-term infants and they reached the first word later than the full-term infants.     

Development of nocturnal sleep behaviors in very low birth infants

The objective of this study is to identify the developmental changes in nocturnal sleep behaviors among preterm infants in comparison with full-term infants (control group). The subjects were 18 preterm infants and 23 full-term infants with mean gestational weeks of 26.5 +/- 2.3 and 39.1 +/- 1.3, and average weights of 879 +/- 188 g and 2,940 +/- 352 g, respectively. Sleep measures were obtained through Actigraph (Micro-mini RC, Ambulatory Monitoring Inc., Ardsley, NY) over a week-long period. Results showed that the sleep duration was significantly different depending on the corrected age of months in only the preterm group (Preterm group: 504 +/- 55 min in under 12 months group, 543 +/- 68 min in over 13 months group. Full-term group: 548 +/- 68 min in under 12 months group, 544 +/- 79 min in over 13 months group). ACTX (percentage of minutes with higher than 0 activity score) was significantly higher for the preterm infants at both age groups in months. In conclusion, the nocturnal sleep duration of preterm infants reached the same level as those of full-term infants after the age of 13 corrected months. Also preterm infants were found to have a higher percentage of less restful sleep during nighttime. Further research is needed to understand the developmental course of physical activity during night time of preterm infants.     

GRATING ACUITY AND VISUAL FIELD DEVELOPMENT OF INFANTS WITH BRONCHOPULMONARY DYSPLASIA

The grating acuity and visual fields were assessed of 48 infants with bronchopulmonary dysplasia (BPD) who had no periventricular leukomalacia or grade III or IV intraventricular hemorrhage, and no stage 3 or greater retinopathy of prematurity. Infants were tested at four, eight, 11, 17 and 24 months corrected age, and their results were compared with those of 81 healthy preterm infants and 54 with hyaline membrane disease (HMD) that did not result in BPD. The BPD group showed no significant difference in acuity development compared with the healthy preterm and HMD groups. Infants with BPD had significantly smaller visual fields than either control group at 11 months; visual field development was similar for all groups at all other test ages. The authors conclude that infants with BPD who have no significant ocular or neurological complications show normal grating acuity and visual field development during the first two years of life.     

Using the Alberta Infant Motor Scale to early identify very low-birth-weight infants with cystic periventricular leukomalacia

We examined whether the Alberta Infant Motor Scale (AIMS) is able to identify very low-birth-weight (VLBW) preterm infants with cystic periventricular leukomalacia (PVL) as early as 6 months of corrected age. Longitudinal follow-up AIMS assessments were done at 6, 12, and 18 months old for 35 VLBW infants with cystic PVL (cPVL⁺), 70 VLBW infants without cystic PVL (cPVL⁻), and 76 term infants (healthy controls: HC). Corrected age was used for the preterm infants. The cPVL⁺ group had significantly lower prone, supine and sitting subscales at age 6, 12, and 18 months than the cPVL⁻ group (all p < 0.05). The cPVL⁻ group showed significantly lower supine, prone, sitting, and standing subscales than the HC group only at age 6 months. At age 6 months, the areas under the receiver operator curve used to discriminate the cPVL⁺ infants from cPVL⁻ infants were 0.82 ± 0.04 for prone, 0.93 ± 0.02 for supine, 0.83 ± 0.05 for sitting, and 0.62 ± 0.07 for standing. The AIMS may help early identify VLBW infants with cystic PVL at age 6 months old.     

NEURODEVELOPMENTAL AND MEDICAL STATUS OF LOW-BIRTHWEIGHT SURVIVORS OF BRONCHOPULMONARY DYSPLASIA AT 10 TO 12 YEARS OF AGE

Thirty low-birthweight (less than 1500g) infants (15 with bronchopulmonary dysplasia (BPD), and 15 controls less than or equal to 5 days O2) and 15 fullterm controls were evaluated at 10 to 12 years of age. BPD children weighted less than fullterm children and had smaller head circumferences than either preterm or fullterm controls. They also had significantly more neurological abnormality than both control groups. BPD children and preterm controls had lower WISC-R arithmetic scores and lower Beery VMI scores, as well as greater need of resources and special education compared with fullterm controls. BPD survivors at 10 to 12 years of age continue to manifest sequelae related to their early pulmonary disease.     

Bronchopulmonary dysplasia predicts adverse developmental and clinical outcomes in very-low-birthweight infants

This study examined the developmental and clinical outcomes in very-low-birthweight (VLBW; < or =1500g) infants with and without bronchopulmonary dysplasia (BPD) throughout infancy, and assessed if BPD predicted poor developmental outcome beyond the effects of other risk factors. One hundred and three VLBW infants (53 males, 50 females; mean gestational age 28wks [SD 2] birthweight 1041g [SD 261]) were graded for severity of BPD according to the American National Institutes of Health (NIH) consensus definition. Neuro-development was assessed using the Neonatal Neurobehavioral Examination-Chinese version, at 36 and 39 weeks' postmenstrual age, and the 2nd edition of the Bayley Scales of Infant Development at 6 and 12 months' corrected age. Clinical outcome was measured by means of rehospitalization for pulmonary causes and treatment with pulmonary medications. Compared with infants without BPD, infants with BPD had higher rates of clinical morbidity, and those with severe BPD further exhibited higher incidences of developmental delay throughout infancy. BPD predicts poor 1-year developmental and clinical outcomes in VLBW infants for which effects are well correlated to the NIH consensus definition.     

SOMATOSENSORY EVOKED POTENTIALS PREDICT NEUROMOTOR OUTCOME AFTER PERIVENTRICULAR HEMORRHAGE

Thirty-nine very low-birthweight (VLBW) preterm infants with periventricular hemorrhage (PVH) were studied with short-latency median nerve somatosensory evoked potentials (SEP) at two, four and/or six months corrected age, and subsequently were followed to a mean age of 22 months. All 12 infants with a single SEP showing unilateral absence or prolonged latency of the early cerebral (N1) response had motor abnormalities at follow-up. A single normal SEP predicted normal motor development in 19 of 36 infants; two normal SEPs did so in 15 of 26 infants, and three normal SEPs in 12 of 14 infants. These results demonstrate that SEPs play a useful r?le in predicting neuromotor outcome for VLBW preterm infants with PVH.     

Parenting stress in families with very low birth weight preterm infants in early infancy

Taking care of a premature infant adds an extra burden to already stressed parents. Previous studies have shown that parental stress occurs during the initial hospitalization. However, there is little information on parental stress over time, and the few existing results are conflicting. In addition, many studies have focused on maternal stress but there is little information about a father's long-term adaptation to stress. The purpose of this study was to examine the degree and type of parenting stress in the families of very low birth weight (VLBW) preterm infants over the first two years of life. We compared parenting stress in families with preterm infants with control families, while also comparing the stress in mothers to that in fathers. Furthermore, we explored the relationship between parenting stress in the preterm group with identified factors that included the infant's age, medical complications, and parents’ perceived feeding issues after they had been discharged from the hospital. This was an exploratory study with a cross sectional design. Participants included a total of 505 mothers from Tainan, Taiwan; 297 with preterm children (239 mothers, 58 fathers) and 208 with full-term children (181 mothers, 27 fathers). Assessments including the Parenting Stress Index, Neonatal Medical Index and Behavior-based Feeding Questionnaire were used to measure parental distress, infants’ medical complications and parents’ perceived feeding issues, respectively. Results of the study, though not statistically significant, indicated the presence of increased parenting stress in parents of preterm infants as compared to parents of full-term infants. 13.1% of mothers with preterm infants demonstrated total stress levels that warranted clinical intervention. We also found that mothers of preterm infants presented different parenting stress patterns than fathers of preterm infants. Fathers of preterm infants tended to have overall higher stress scores than mothers. On the other hand, mothers of preterm infants tended to report more health related difficulties, more depression, higher social isolation and role restriction, and less support from their spouses, than reported by fathers. Moreover, as time went on, parents with preterm infants continued to experience greater parenting stress than those with full-term infants. Understanding the experiences of parents with preterm children is important for health care providers while interviewing parents for information regarding their children and designing intervention programs to improve children's outcomes.     

Motor development and sleep, play, and feeding positions in very-low-birthweight infants with and without white matter disease

We investigated the association of infants' sleep and awake positioning with motor milestone acquisition as measured by the Alberta Infant Motor Scale (AIMS). Participants were 30 very-low-birthweight (VLBW) infants with preterm white matter disease (PTWMD; 21 males, nine females; mean birthweight [BW] 1,129 g [SD 338]; mean gestational age [GA] 28 wks [SD 2.44]); 21 VLBW infants without preterm WMD (PT; 13 males, eight females; mean BW 1,107 g [SD 370]; mean GA 28.05 wks [SD 2.21]); and 17 term infants (Term; seven males, 10 females; mean BW 3,565 g [SD 382]; mean GA 40 wks [SD 1.31]). Testing occurred at 1, 5, and 9 months of age (corrected for prematurity). Preferred positions during sleeping, playing, and feeding were obtained through parent interview. These positions and group were the independent variables. Prone sleeping was significantly and positively associated with motor development at all ages (1 mo: p=0.005; 5 mo: p=0.011; 9 mo: p=0.040). At 5 months, prone sleeping and playing were significantly and positively associated with AIMS scores (prone sleeping, p=0.016; prone playing, p=0.047). However, group was negatively associated with preterm white matter disease, with the PTWMD group having significantly lower AIMS scores than the Term group (p=0.029). At 9 months, sitting playing and group membership were significantly associated with AIMS scores (sitting playing, p=0.005; group, p=0.012). Prone positioning should be encouraged for awake time, particularly for infants with preterm white matter disease.     

Intervention effects on emotion regulation in preterm infants with very low birth weight: A randomize controlled trial

Preterm infants are at risk for emotional difficulties and behavioral problems. This study was aimed to investigate the effects of a clinic-based intervention program (CBIP) and a home-based intervention program (HBIP) compared with a usual care program (UCP) on emotion regulation to stress in preterm infants with very low birth weight (VLBW, birth weight <1500 g). A total of 178 VLBW preterm infants had been previously randomly assigned to receive one of three interventions (57 in CBIP, 63 in HBIP and 58 in UCP). The CBIP and HBIP contained identical child-, parent- and dyad-focused interventions that were provided to infants during hospitalization and were respectively delivered at clinics and at home at PMA 36–38 and 40 weeks, and 1, 2, 4, 6, 9, 12 months of corrected age. All infants were prospectively observed for behavioral reactivity and regulation in response to experimentally evoke stress evoked by a toy-behind-barrier procedure at 12, 18, and 24 months of corrected age. Their cognitive and language abilities, and mothers’ responsiveness were also assessed at 12 months as potential covariates. Compared to the UCP-group infants, the HBIP-group infants exhibited shorter durations of visual orientation to a toy (adjusted difference [95% CI] = −1.60 [−3.07 to −0.13], p = 0.03), and the CBIP-group infants exhibited shorter durations of avoidance (adjusted difference [95% CI] = −0.84 [−1.57 to −0.10], p = 0.03) from 12 to 24 months of corrected age. The CBIP and HBIP showed no difference in the stress reactivity from the UCP, however. These results suggest that comprehensive interventions incorporating child-, parent- and dyad-focused services enhanced VLBW preterm infants’ emotion regulation in response to stress at toddler age.     

Cortisol, contingency learning, and memory in preterm and full-term infants

Cortisol plays an important role in learning and memory. An inverted-U shaped function has been proposed to account for the positive and negative effects of cortisol on cognitive performance and memory in adults, such that too little or too much impair but moderate amounts facilitate performance. Whether such relationships between cortisol and mental function apply to early infancy, when cortisol secretion, learning, and memory undergo rapid developmental changes, is unknown. We compared relationships between learning/memory and cortisol in preterm and full-term infants and examined whether a greater risk for adrenal insufficiency associated with prematurity produces differential cortisol-memory relationships. Learning in three-month old (corrected for gestational age) preterm and full-term infants was evaluated using a conjugate reinforcement mobile task. Memory was tested by repeating the same task 24h later. Salivary cortisol samples were collected before and 20 min after the presentation of the mobile. We found that preterm infants had lower cortisol levels and smaller cortisol responses than full-term infants. This is consistent with relative adrenal insufficiency reported in the neonatal period. Infants who showed increased cortisol levels from 0 to 20 min on Day 1 had significantly better memory, regardless of prematurity, than infants who showed decreased cortisol levels.     

Abnormalities in the coordination of respiration and swallow in preterm infants with bronchopulmonary dysplasia

Individual rhythms of suck, swallow, and respiration are disrupted in preterm infants with bronchopulmonary dysplasia (BPD). Integration of respiration into suck-swallow efforts is critical for establishing coordinated suckle feeding. This study quantitatively assessed the coordination of respiration and swallow in infants with and without BPD. Thirty-four preterm infants of 26 to 33 weeks' gestational age were included: 14 participants with BPD (eight males, six females)and 20 comparison participants without BDP (10 males, 10 females). Participants were studied at postmenstrual age 32 to 40 weeks and postnatal age 2 to 12 weeks using digital recordings of pharyngeal pressure, nasal thermistor flow, and thoraco-abdominal plethysmography. The coefficients of variation (COV; standard deviation/mean) of the swallow-breath (SW-BR) and breath-breath (BR-BR) intervals during swallow runs, the percentage of 'apneic swallows' (runs of >or=3 swallows without interposed breaths), and phase relationships of respiration and swallow were used to quantify rhythmic coordination and integration of respiration into feeding episodes. Apneic swallows were significantly increased after 35 weeks in infants with BPD (mean 13.4% [SE 2.4]) compared with non-BDP infants (6.7% [SE 1.8]; p<0.05), as were SW-BR phase relationships involving apnea. The BPD cohort also had significantly higher SW-BR COV and BR-BR COV than non-BPD infants, indicating less rhythmic coordination of swallowing and respiration during feeding. Results emphasize the need for frequent rests and closer monitoring when feeding infants with respiratory compromise. Quantitative assessment of the underlying rhythms involved in feeding may be predictive of longer-term feeding and neurological problems.     

Cervical accelerometry in preterm infants with and without bronchopulmonary dysplasia

Cervical accelerometry with digital signal processing (DSP) can identify signals that are consistently associated with swallowing during feeding of infants. It is shown that these signals, called initial discrete sounds (IDSs), become more uniform with advancing postmenstrual age (PMA) in healthy preterm infants. The objectives of this study were to determine if cervical accelerometry and DSP at a higher sample rate than previously used (22 kHz versus 16 kHz), in conjunction with a DSP software package that allows manipulation of the sound files, would improve the accuracy of the previously developed variance index (VI) method of analyzing accelerometric information. The modified VI method was then used to measure developmental differences in the IDS morphology of infants with and without bronchopulmonary dysplasia (BPD). VIs were calculated for 24 feeding studies of infants of between 32 and 39 weeks PMA: 12 studies on healthy preterm infants (n = 10: three males, seven females; mean gestational age [GA] 28.6 weeks, SD 0.4; mean birthweight [BW] 1080 g, SD 82; PMA mean 35.2 weeks, SD 0.6) and 12 studies on infants with BPD (n = 7: five males, two females; GA 27.1 weeks, SD 0.4; BW 911 g, SD 71; PMA 36.2 weeks, SD 0.6). There was a significant inverse correlation between VI and PMA for the healthy preterm group (r = 0.66, m = -2.31/week,p = 0.02). There was no significant correlation between VI and PMA for the BPD cohort. The VI of infants with BPD was significantly different from that of infants without BPD (p < 0.007, multiple regression analysis, interaction PMA x Group). Additionally, using our modified VI technique, 100% of swallows were found to have the expected IDS signals.     

Visual field and grating acuity development in low-risk preterm infants during the first 2 1/2 years after term.

The effect of early visual experience on visual field size and grating acuity development was studied longitudinally in 36 appropriate for gestational age (AGA) and 26 small for gestational age (SGA) low-risk preterm infants. These were selected out of 194 very low birth weight (VLBW) infants (birthweight less than 1500 g) born in 1985 and 1986. Criteria for inclusion as low-risk were the absence of neurological, respiratory, circulatory and alimentary problems in the neonatal period; no retinopathy of prematurity and no evidence of abnormality on the neonatal cranial ultrasound scans. Binocular field sizes were assessed using kinetic arc perimetry. Binocular grating acuity was tested by means of the prototype version of the acuity card procedure. Results were compared with norms obtained in control fullterms in earlier studies. Infants were tested at 6 weeks, 6, 6, 9 and 12 months of age from the expected term date. Twenty-two of these infants were retested at 2 1/2 years of corrected age. Visual field size and visual acuity estimates of (both AGA and SGA) low-risk, VLBW preterms and control fullterms overlapped at all test ages, except for a slight but significantly faster development of the upper and the lower visual field at 6 weeks corrected age in the preterm group. These results indicate that for clinical purposes visual experience before the expected term date has not only no measurable effect on the normal development of behavioural acuity, but also no accelerating effect on the development of peripheral vision.     

Sleep patterns,problems, and ecology in young children born preterm and full-term and their mothers

BackgroundPrevious studies of sleep patterns and problems in preterm infants compared to full-term infants have yielded mixed results, with little known about sleep ecology. The aims of this study were to compare sleep patterns, sleep problems, and sleep ecology across developmental stages (birth to 36 months) in preterm (3 or more weeks early) infants and toddlers to those born full-term, in addition to their mothers’ sleep.MethodsMothers of 834 young children in Brazil (ages 0–35.9 months), half preterm and half full-term (matched for sex and chronological age), completed the Brief Infant Sleep Questionnaire and the Pittsburgh Sleep Quality Index.ResultsAcross the entire sample, preterm and full-term infants were similar for most sleep parameters, including sleep onset latency, number and duration of night awakenings, and sleep duration, as well as sleep ecology parameters, including falling asleep independently and sleep location. However, preterm infants were more likely to be held to initiate sleep, given a bottle to resume sleep after waking, and less likely to be breastfed to resume sleep after waking. Mothers of preterm infants, however, were more likely to report a parent-perceived sleep problem, although maternal-perceived confidence in managing child sleep and bedtime difficulty were similar. Finally, maternal sleep parameters were similar between groups.ConclusionsOverall, these results indicate that sleep patterns, sleep problems, and sleep ecology among preterm infants and toddlers and their mothers are largely similar to those of full-term infants and toddlers and their mothers, even within the first few months.     

Integration of suck and swallow rhythms during feeding in preterm infants with and without bronchopulmonary dysplasia

The aim of this study was to define quantitative measures for assessing the integration and maturation of suck and swallow rhythms in preterm infants as they relate to each other. Fourteen preterm infants (eight males, six females; gestational age range 26 to 32 weeks) with bronchopulmonary dysplasia (BPD) and an age-matched cohort of 20 infants (10 males, 10 females; gestational age range 26 to 33 weeks) without BPD were studied weekly from time of initiation of oral feeding using simultaneous recordings of nipple and pharyngeal pressure. The integration of suck and swallow rhythms was quantified by using the coefficient of variation (COV) of the suck-swallow dyad interval. Infants without BPD had a significant correlation between increasing postmenstrual age (PMA) and decreasing COV of the dyadic interval (increasing stabilization; r=0.45; p=0.008). In the non-BPD cohort 35 weeks or less PMA, the mean dyadic COV was 0.42 (SD 0.12) versus 0.34 (SD 0.09) in those more than 35 weeks PMA (p=0.039). In contrast, dyadic stability in infants with BPD was not correlated with PMA. Infants with BPD of more than 35 weeks PMA had less dyadic stability (0.45, SD 0.10) than did age-matched controls (p<0.001). Dyadic stability was also correlated with feeding efficiency in the non-BPD group (r=0.46;p=0.007) but not in the BPD cohort. Therefore, ontogeny of rhythmic suckle feeding can be described quantitatively in preterm infants, allowing comparison with at-risk populations. Infants with BPD do not follow predicted maturational patterns of suck-swallow rhythmic integration.