Abstract  In 1994, Stanford University's Exposure Research Group (ERG) conducted its first pilot study to collect micro-level activity time series (MLATS) data for young children. The pilot study involved videotaping four children of farm workers in the Salinas Valley of California and converting their videotaped activities to valuable text files of contact behavior using video-translation techniques. These MLATS are especially useful for describing intermittent dermal (i.e., second-by-second account of surfaces and objects contacted) and non-dietary ingestion (second-by-second account of objects or hands placed in the mouth) contact behavior. Second-by-second records of children contact behavior are amenable to quantitative and statistical analysis and allow for more accurate model estimates of human exposure and dose to environmental contaminants. Activity patterns data for modeling inhalation exposure (i.e., accounts of microenvironments visited) can also be extracted from the MLATS data. Since the pilot study, ERG has collected an immense MLATS data set for 92 children using more developed and refined videotaping and video-translation methodologies. This paper describes all aspects required for the collection of MLATS including: subject recruitment techniques, videotaping and video-translation processes, and potential data analysis. This paper also describes the quality assurance steps employed for these new MLATS projects, including: training, data management, and the application of interobserver and intraobserver agreement during video translation. The discussion of these issues and ERG's experiences in dealing with them can assist other groups in the conduct of research that employs these more quantitative techniques.

Abstract  Thirty-three hours of videotape collected in a 1993 pilot study were quantified, via a video translation software application, to obtain left and right hand activity data of four children of farmworkers. Reported here are the children's contact duration and frequency for each object in their environment, duration spent in each location and activity exertion level, and frequency distributions of object contact durations. The pilot study provided valuable information for evaluating and improving videotaping and videotape translation methodologies as a means of gathering activity information that can be used to refine dermal exposure estimates. Although a larger database of children's videotaped activities for different ages and populations is needed before generalizations can be made, the data presented here are the most detailed information to date for children's micro-level dermal activities.

Abstract  Questionnaires and diaries, the current methods of human activity data collection, do not accurately capture the detail necessary to quantify exposure incurred through the dermal and non-dietary ingestion routes. Stanford University's Environmental Engineering and Science Program has developed methodologies and software (VideoTraq) for training video translators, determining inter-observer reliability, and translating videotaped micro-activity patterns into computer text files. VideoTraq output files contain duration, in seconds, for each combination of location, activity, and object contacted corresponding to the sequential micro-activities of a videotaped subject's contact boundary (e.g., left hand, right hand, mouth). Such output allows for detailed analyses of micro-activity data, including contact frequency and duration. When coupled with environmental concentrations, these data will allow for more accurate exposure assessments, particularly for the dermal and non-dietary ingestion exposure routes.

Abstract  Because of their mouthing behaviors, children have a higher potential for exposure to available chemicals through the nondietary ingestion route; thus, frequency of hand-to-mouth activity is an important variable for exposure assessments. Such data are limited and difficult to collect. Few published studies report such information, and the studies that have been conducted used different data collection approaches (e.g., videography versus real-time observation), data analysis and reporting methods, ages of children, locations, and even definitions of "mouthing." For this article, hand-to-mouth frequency data were gathered from 9 available studies representing 429 subjects and more than 2,000 hours of behavior observation. A meta-analysis was conducted to study differences in hand-to-mouth frequency based on study, age group, gender, and location (indoor vs. outdoor), to fit variability and uncertainty distributions that can be used in probabilistic exposure assessments, and to identify any data gaps. Results of this analysis indicate that age and location are important for hand-to-mouth frequency, but study and gender are not. As age increases, both indoor and outdoor hand-to-mouth frequencies decrease. Hand-to-mouth behavior is significantly greater indoors than outdoors. For both indoor and outdoor hand-to-mouth frequencies, interpersonal, and intra-personal variability are approximately 60% and approximately 30%, respectively. The variance difference among different studies is much bigger than its mean, indicating that different studies with different methodologies have similar central values. Weibull distributions best fit the observed data for the different variables considered and are presented in this article by study, age group, and location. Average indoor hand-to-mouth behavior ranged from 6.7 to 28.0 contacts/hour, with the lowest value corresponding to the 6 to <11 year olds and the highest value corresponding to the 3 to <6 month olds. Average outdoor hand-to-mouth frequency ranged from 2.9 to 14.5 contacts/hour, with the lowest value corresponding to the 6 to <11 year olds and the highest value corresponding to the 6 to <12 month olds. The analysis highlights the need for additional hand-to-mouth data for the <3 months, 3 to <6 months, and 3 to <6 year age groups using standardized collection and analysis because of lack of data or high uncertainty in available data. This is the first publication to report Weibull distributions as the best fitting distribution for hand-to-mouth frequency; using the best fitting exposure factor distribution will help improve estimates of exposure. The analyses also represent a first comprehensive effort to fit hand-to-mouth frequency variability and uncertainty distributions by indoor/outdoor location and by age groups, using the new standard set of age groups recommended by the U.S. Environmental Protection Agency for assessing childhood exposures. Thus, the data presented in this article can be used to update the U.S. EPA's Child-Specific Exposure Factors Handbook and to improve estimates of nondietary ingestion in probabilistic exposure modeling.

Abstract  To improve estimates of non-dietary ingestion in probabilistic exposure modeling, a meta-analysis of children's object-to-mouth frequency was conducted using data from seven available studies representing 438 participants and approximately 1500 h of behavior observation. The analysis represents the first comprehensive effort to fit object-to-mouth frequency variability and uncertainty distributions by indoor/outdoor location and by age groups recommended by the US Environmental Protection Agency for assessing childhood exposures. Weibull distributions best fit the observed data from studies with no statistical differences, and are presented by study, age group, and location. As age increases, both indoor and outdoor object-to-mouth frequencies decrease. Object-to-mouth frequency is significantly greater indoors (2-32 contacts/h) than outdoors (average 1-9 contacts/h). This paper compares results to a similar hand-to-mouth frequency meta-analysis. Children who tend to mouth hands indoors also tend to mouth hands outdoors; children who tend to mouth objects indoors tend to mouth objects outdoors. However, children who tend to mouth objects do not necessarily have a tendency to mouth hands. Unlike for hand-to-mouth frequency, a statistical difference was found among the various studies for object-to-mouth frequency. This could be due to different definitions for object mouthing across the studies considered. The analysis highlights the need for additional object-to-mouth data (indoors and especially outdoors) for various age groups using standardized collection and analysis.

Abstract  OBJECTIVE: Mouthing behavior in infants and young children <3 years old is a poorly quantified yet normal part of early childhood development. Increasingly, safety and risk assessments involving materials that may be mouthed depend on accurate estimates of oral contact time. This study reports the results of an observational study performed to investigate and obtain data on mouthing behavior of objects for children up to 3 years old.

METHODOLOGY: The study used a standard diary form with instructions for participating parents to observe their child in a normal environment (primarily home), and to document both the type and duration of each item mouthed. Phase I (pilot) consisted of 30 children each observed for 1 day, divided equally between the ages of 0 to 18 months (n = 15) and 19 to 36 months (n = 15), whereas Phase II included more participants (n = 92 aged 0-18 months; n = 95 aged 19-36 months). Phase III included observations for 5 nonconsecutive days over a 2-month period on 168 children between the ages of 3 to 18 months (at study initiation), and focused on total mouthing time of objects, exclusive of pacifiers.

RESULTS: The data collected during the first 2 phases were pooled and analyzed together. For all participants between the ages of 0 and 18 months (n = 107), the average daily duration of mouthing objects included: pacifiers (108 minutes), plastic toys (17 minutes), teethers (6 minutes), and other objects (9 minutes). The results for children 19 to 36 months old (n = 110) included: pacifiers (126 minutes), plastic toys (2 minutes), teethers (0 minutes), and other objects (2 minutes). Although no significant difference existed between the 2 age ranges for pacifier mouthing duration, a statistically significant difference was observed for nonpacifier objects. For Phase III, the average daily mouthing time for all objects (excluding pacifiers), based on 5 nonconsecutive days of observation for 168 children, was 36 minutes (n = 793 valid child observation days).

CONCLUSIONS: Results of this study indicate that mouthing behavior is dependent on age and the types of items that are mouthed. Duration of mouthing varies among children, with some consistently not mouthing any objects and with a very small number mouthing objects for >2 hours a day. The study also revealed wide variability in the types of objects mouthed, including many nontoy objects. Children mouth pacifiers significantly longer than other objects, regardless of age. Significantly increased mouthing time of all nonpacifier objects is reported for children in the 0- to 18-month range compared with the 19- to 36-month range.

Abstract  Ingestion of non-food items/mouthing behavior results in exposure of children to contaminants in soil/dust. We characterize the prevalence of such behaviors in healthy children. The relative frequency of such behaviors was assessed by parent interviews for 533 children age 1 to 6. Thirty-eight percent of children put soil in their mouths at least monthly, 24% at least weekly, and 11% daily. High-risk behavior decreased quickly for children aged 2 or more, but was still reported at least monthly by 3 to 9% of parents of children up through age 6. Highest outdoor object mouthing rates occur among 1-year-old children, who are reported to play daily in sand/dirt and have generally high levels of mouthing. Such children may have higher soil/dust ingestion and higher exposure to contaminants when soil/dust contains lead or other agents. These high-risk groups may help focus educational interventions and/or risk assessments.

Abstract  Hand-mouth coordination was studied in 1–3-day-old human infants by delivering 0.2 ml of sterile 12% sucrose solution intraorally once every 2 min. Sucrose was extraordinarily calming and caused sustained hand-in-mouth contact. The calm state persisted well beyond sucrose termination. Hand-in-mouth behavior, however, stopped upon sucrose termination, demonstrating stimulus control over this integrated behavior. In subsequent studies we demonstrated that hand-in-mouth behavior was not attributable to calming per se. Moreover, hand activity could be prevented by placing a pacifier in the mouth. This demonstrates that the behavior was under intraoral somesthetic control and was not necessarily the expression of a motor pattern triggered by the sweet taste. These findings are interpreted within the contexts of sucrose (a) calming through an endogenous opioid system and (b) activating suckling-feeding mechanisms, causing the expression of integrated hand, mouth, and head motor patterns.

Abstract  Non-dietary ingestion exposure, defined as contact between the inside of the mouth and non-food items such as fingers, toys, dirt, and other objects, may be a significant route of exposure and source of subsequent health risk for young children. Questionnaires and diaries, the current conventional methods for collecting activity data, cannot capture the detail necessary to quantify mouthing behavior relevant to non-dietary ingestion exposure. New video translation methodologies and computer software have been applied to 31 hours of video tapes (6.0, 6.6, 8.4, and 10.1 waking hours of four children), yielding detailed object-to-mouth contact duration and frequency information for children aged two to four. The collected data reveal that the four children inserted non-dietary items into their mouth between 1 and 7% of the time they were videotaped on the study day: the median mouth contact duration over all non-dietary object categories ranged from 2 to 4 seconds; the total percentage of contacts that lasted for less than or equal to ten seconds ranged from 73% to 87%; and the median frequencies of mouth contact with non-dietary objects for the four children ranged from 2 to 20 contacts per hour. Non-dietary objects mouthed most frequently by the children were skin, hard toys, hard surfaces, and photographs. The mean ratio for the four children of the total percent time that the children placed non-dietary objects in the mouth to total percent time that food and other diet-related objects were placed inside the mouth was 0.24.

Abstract  The National Human Exposure Assessment Survey (NHEXAS)/Minnesota Children's Pesticide Exposure Study (MNCPES) was a population-based study designed to characterize children's exposure to residential pesticides and to evaluate the contribution of residential and children's activities to children's exposure. Families of 168 children were surveyed for residential use of pesticides and children's activities. From these homes, families of 102 children between the ages of 3 and 13 years participated in a week-long intensive exposure study. Of the 102 children, 19 children were videotaped for four consecutive hours in their normal daily activities. The survey responses indicated that the youngest children were more likely to exhibit behaviors that would foster exposure to environmental contaminants. Comparison of questionnaire responses indicated that the videotaped subsample was representative of the exposure study population. The microactivities of the videotaped children that might contribute to their exposure via ingestion or dermal routes were quantified. Hand-to-mouth and object-to-mouth activities were observed most frequently among the youngest children. The youngest children were also most likely to be barefoot both indoors and outside. Gender differences were found in mouthing behavior and the proportion of observed time spent outdoors.

Abstract  Childrens' touching and mouthing behaviors during outdoor play in urban residential yards were measured using video observations. Descriptions were made of childrens' outdoor residential play environments. Behaviors assessed were used to examine (1) validity of parental responses to questions on childrens' oral behaviors and outdoor play and (2) relationships of mouthing behaviors to blood lead levels (BLLs). Thirty-seven children aged 1-5 years were recruited for 2 h of video recording in their yard and blood lead measurement. Video assessments included hourly rates of hand touches to ground/ walking-level surfaces (cement/stone/steel, porch floor/steps, grass, and bare soil) and oral behaviors. Parental questionnaires assessed their child's outdoor activities, behaviors, and home environment. The children were: mean 39 months; 51% male; 89% Hispanic; and 78% Medicaid or uninsured. Twenty-two children had a blood lead measured (mean 6 m mu/dl). During taping, all children had access to cement, 92% to grass, 73% to bare soil, and 59% to an open porch. Children had frequent touching and mouthing behaviors observed (median touches/h: touches to surfaces 81; hand-to-mouth area (with and without food) 26; hand-in-mouth 7; and object-in-mouth 17). Blood lead was directly correlated with log-transformed rates of hand-in-mouth (Pearson's correlation, r = 0.564, n = 22, P = 0.006) and object-in-mouth (Pearson's correlation, r = 0.482, n = 22, P = 0.023) behaviors. Parental questionnaire responses did not accurately reflect childrens' observed oral behaviors, play habits, or play environment. These data confirm the direct relationship between hand-to-mouth activities and BLLs and fail to validate parental perceptions of their child's mouthing behaviors or outdoor play environment.

Abstract  This paper reviews studies investigating the assessment and treatment of hand mouthing in individuals with severe to profound developmental disabilities. A literature search identified 101 studies carried out between 1969 and 2004. The trend in the studies indicated a shift away from aversive interventions in the last 10 years, so this review included studies conducted from 1995. Twenty-three studies were identified within this period and were included in this review. The 23 studies were sorted into seven intervention categories and one assessment category. The seven intervention categories included (a) antecedent interventions, (b) multicomponent interventions (e.g., differential reinforcement and response effort), (c) pharmacological interventions, (d) interventions that utilized reinforcement, (e) response blocking interventions, (f) response effort interventions, and (g) sensory stimulation interventions. The one assessment category included studies that investigated the function of hand mouthing. One main finding in these studies was that the various intervention strategies led to decreases in hand mouthing in individuals with severe to profound developmental disabilities. This finding is discussed in relation to its effect on issues of health, adaptive behavior, and social functioning. A second finding indicated that hand mouthing is often maintained by automatic reinforcement (i.e., non-social contingencies). The implications of this finding are discussed in terms of how assessments and treatments associated with automatically maintained challenging behavior might be more effectively linked. Potential issues for future research are also examined.

Abstract  A substantial portion of human respiratory tract infection is thought to be transmitted via contaminated hand contact with the mouth, eyes, and/or nostrils. Thus, a key risk factor for infection transmission should be the rate of hand contact with these areas termed target facial membranes. A study was conducted in which 10 subjects were each videotaped for 3 hr while performing office-type work in isolation from other persons. The number of contacts to the eyes, nostrils, and lips was scored during subsequent viewing of the tapes. The total contacts per subject had sample mean x = 47 and sample standard deviation s = 34. The average total contact rate per hour was 15.7. The authors developed a relatively simple algebraic model for estimating the dose of pathogens transferred to target facial membranes during a defined exposure period. The model considers the rate of pathogen transfer to the hands via contact with contaminated environmental surfaces, and the rate of pathogen loss from the hands due to pathogen die-off and transfer from the hands to environmental surfaces and to target facial membranes during touching. The estimation of infection risk due to this dose also is discussed. A hypothetical but plausible example involving influenza A virus transmission is presented to illustrate the model.

Abstract  Young children have a natural tendency to mouth items to explore their environment. Mouthing carries mechanical and chemical hazard potential for injury to the child, for example if they swallow an item they may choke, they may cut themselves on sharp items, and certain chemicals are present in plastic items which may pose a risk to children. Few data are available on the time that young children mouth items, how they mouth, and what they mouth. This study gathered data on 236 children aged between 1 month and 5 years to supplement and extend existing data. Findings are presented of estimated average and maximum daily mouthing times for children, how they mouth, what they mouth, and whether the items mouthed were intended to be. A validation study was carried out to determine the accuracy of the parental observation method used to gather the data. The implications of the findings of this study are discussed with respect to reducing the potential for mechanical accidents in the home.

Abstract  A videotaping methodology has been developed for use in quantifying the types and frequencies of children's hand and mouthing activities that could lead to exposure to environmental pollutants via dermal and ingestion pathways. Twenty children in day care, ages 3-6 years and 10 children in residences, ages 2-5 years, were videotaped during their waking hours for 1 day. Parents of each child completed questionnaires for the purpose of evaluating the accuracy of parental reports of hand-to-mouth rates. Videotapes were translated as quantifiable activities by two trained observers whose reporting reliability was checked throughout the investigation. Results determined that reliability of the videotaping method was very good, even over a year post-training. From videotape data, the average hand-to-mouth frequency rate was determined to be 9.5 contacts/h. These values are considerably higher than the current default value of 1.56 contacts/h under consideration by the EPA.

Abstract  Young children may be more likely than adults to be exposed to pesticides following a residential application as a result of hand- and object-to-mouth contacts in contaminated areas. However, relatively few studies have specifically evaluated mouthing behavior in children less than 5 years of age. Previously unpublished data collected by the Fred Hutchinson Cancer Research Center (FHCRC) were analyzed to assess the mouthing behavior of 72 children (37 males/35 females). Total mouthing behavior data included the daily frequency of both mouth and tongue contacts with hands, other body parts, surfaces, natural objects, and toys. Eating events were excluded. Children ranged in age from 11 to 60 months. Observations for more than 1 day were available for 78% of the children. The total data set was disaggregated by gender into five age groups (10-20, 20-30, 30-40, 40-50, 50-60 months). Statistical analyses of the data were then undertaken to determine if significant differences existed among the age/gender subgroups in the sample. A mixed effects linear model was used to test the associations among age, gender, and mouthing frequencies. Subjects were treated as random and independent, and intrasubject variability was accounted for with an autocorrelation function. Results indicated that there was no association between mouthing frequency and gender. However, a clear relationship was observed between mouthing frequency and age. Using a tree analysis, two distinct groups could be identified: children < or = 24 and children >24 months of age. Children < or = 24 months exhibited the highest frequency of mouthing behavior with 81+/-7 events/h (mean+/-SE) (n=28 subjects, 69 observations). Children >24 months exhibited the lowest frequency of mouthing behavior with 42+/-4 events/h (n=44 subjects, 117 observations). These results suggest that children are less likely to place objects into their mouths as they age. These changes in mouthing behavior as a child ages should be accounted for when assessing aggregate exposure to pesticides in the residential environment.

Abstract  A pesticide exposure assessment pilot study was conducted in Salinas Valley, California during September, 1993. The pilot study had two main purposes: 1) to develop general methodologies for videotaping micro-activities of a population, and 2) to collect an initial database of activity patterns of two- to four-year-old farm labor children. Tools to accurately determine exposure and dose through all three pathways (dermal, ingestion, and inhalation) are needed to effectively assess and manage health risks posed by pesticides and other environmental pollutants. Eight to ten hours of videotape data were collected for each of four Mexican-American farm labor children. In addition, the researchers administered a day-after recall questionnaire to the caregivers of the children to test (for the study sample) the hypothesis that recall questionnaires are inadequate for collecting detailed information regarding dermal and hand-to-mouth exposures. The results of this study provide the first detailed set of videotape data on farm labor children, a population at high risk to pesticide exposures. In addition, this is the first project in the exposure assessment field to use direct observation videotaping for collecting micro-activity data in order to quantify dermal and ingestion exposure. The comparison of caregivers' recall of children's activities to actual videotapes from the pilot study supports the hypothesis that videotaping may greatly improve the accuracy of activity information used to compute dermal and ingestion exposures. However, as it was clear that the researchers' presence in some cases altered the activities of the subjects, further experiments need to be conducted to minimize interference of videotaping on exposure-related activities. This paper explains the selection of the study population, the methods used to implement the pilot study, and the lessons learned. While the discussion focuses on four case studies in the Mexican-American farm labor population, the data collection methods developed and the lessons learned can be applied to other populations.

Abstract  This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2-6 h. Video footage was translated into micro-level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/h. The median hand-to-mouth frequency was 15.2 events/h and the median object-to-mouth frequency was 27.2 events/h. The hourly mouthing duration was 1.2 and 2.2 min/h with the hands and objects, respectively. The median mouthing duration with hands and objects was 2 s. The median contact frequency for both hands combined was 689.4 events/h with an hourly contact duration of 100.5 min/h and a median contact duration of 3s. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current US EPA recommendations, questioning their protective value for infants and toddlers.

Abstract  The lead content of air, house dust, dirt, dirt on hands, food, and water was investigated in order to ascertain the cause of the chronically elevated blood lead levels in ten 2–6 year old Hartford children. Recent ingestion of leaded paint had been eliminated as a significant factor. The mean ambient air levels at 2 and 5 ft. from the ground where the children played varied from 1.7–7 μg/m3. On the basis of “mouthing” behavior observed among the ten subject children, the mean lead levels in dirt (1200) μg/g) and dust (11,000 μg/g) and the mean lead concentration of lead on hands (2400) μg/g), it is likely that the “hands in mouth” exposure route is the principal cause of the excessive lead accumulation in these children.

Abstract  An environmental measurement and correlation study of nondietary ingestion of pesticides was carried out in a colonia in south Texas. The purpose of the study was to evaluate young children's exposure to environmental levels of organophosphate (OP) pesticides in the household. Samples were collected to measure levels of OP pesticides in housedust and on children's hands. These, in turn, were compared to levels of OP pesticide metabolites in urine. A total of 52 children, 25 boys and 27 girls, participated in the spring and summer of 2000. The children were 7-53 months of age at the time of recruitment. Univariate and multivariate regression analyses were carried out using SAS statistical software. Seventy-six percent of housedust samples and 50% of hand rinse samples contained OP pesticides. All urine samples had at least one metabolite and over 95% had at least two metabolites above the limit of detection (LOD). Total OP loadings in the housedust ranged from nondetectable (nd) to 78.03 nmol/100 cm2 (mean=0.15 nmol/100 cm2; median=0.07 nmol/100 cm2); total OP loadings on the children's hands ranged from nd to 13.40 nmol/100 cm2 (mean=1.21 nmol/100 cm2; median=1.41 nmol/100 cm2), and creatinine corrected urinary levels (nmol/mol creatinine) of total OP metabolites ranged from 3.2 to 257 nmol/mol creatinine (mean=42.6; median 27.4 nmol/mol creatinine). Urinary metabolites were inversely associated with the age of the child (in months) with the parameter estimate (pe)=-2.11, P=0.0070, and 95% confidence interval -3.60 to -0.61. The multivariate analysis observed a weak association between concentrations of OP pesticides in housedust, loadings in housedust, and concentration on hands, hand surface area, and urinary levels of OP metabolites. However, hand loadings of OP pesticides were more strongly associated (r2=0.28; P=0.0156) with urinary levels of OP metabolites (pe=6.39; 95% CI 0.98-11.80). This study's preliminary findings suggest that surface loadings of pesticides, on hands, are more highly correlated with urinary bioassays and, therefore, may be more useful for estimation of exposure in epidemiologic studies than levels of pesticides in housedust.

Abstract  Recent studies have found that elements of hand–mouth coordination are embedded within the spontaneous general movements of newborns. Little is known about the subsequent development of the coordination, however. The hand–mouth movements of 14 infants were studied longitudinally between 2–5 months of age at monthly intervals. At 4 months of age, contacts on other parts of the face diminished, such that there was a focus on the mouth. Anticipatory mouth opening was not found at 4 months but started to occur at 5 months. These results are accounted for in terms of involuntary general movements, as well as neuromuscular immaturity constraining the expression of hand–mouth coordination before 4 months of age. This pattern of development compares with the related coordination of reaching and grasping.

Abstract  Hand-mouth contacts (HMCs) and other spontaneous movements of five low-risk preterm infants were studied longitudinally after their birth until 60 weeks postmenstrual age. For all infants, HMCs that emerged in the preterm period could not be observed transiently after 45 weeks, however, they re-emerged after 50 weeks postmenstrual age. In actograms of the infants' behaviors, the frequency of other spontaneous movements, such as head rotation, showed the same re-emerging pattern. Movements such as cloni, which were also observed in the preterm period, decreased after the term period, with no subsequent increase. Only general movements were continuously present throughout the entire observation period; these changed from writhing to fidgety in nature around the third month. These findings clarify which spontaneous movements of preterm infants are important for later behavioral development.