In developmental psychology, there has always been a question, “how do new skills come to infants and where do they come from?” Some believe that new skills develop from prior accomplishments; others feel as one skill disappears, the new one quickly appears; some others believe that the skills are based on physical similarity - where old and new skills are similar in form. However, most widely believed theory is the shared psychological function where the old and the new skills rely on the same underlying psychological mechanisms with an objective to achieve the same goals.
We have summarised below six scholarly published articles which have tried to assess the achievement of developmental milestones in infants in different conditions and backgrounds.
Research study 1: Developmental continuity1
A recent research by Adolph and colleagues examined the developmental continuity in infant locomotion between cruising and walking. Through this research, the authors reported three studies that examined transition from cruising to walking in infants. These studies determined the developmental continuity and discontinuity. First study determined the extent of temporal contiguity between walking, cruising, and crawling. The second study determined functional continuity between cruising and walking, while the third study tested infants who had just learnt to take their first walking step. In all three studies, the objective was to see an infant’s ability to detect affordance for movement based on a critical aspect of cruising and a basic necessity for walking. The critical aspect of cruising was determined by gaps in handrail used for manual support and basic necessity for walking was determined by the gaps in the floor under their feet.
In the first study, 603 infants of 14.05 months average age participated. In this study group, cruising and hand and knee crawling was common. On an average, infants began crawling before cruising and did both before walking. In the second study, twenty two 11-month-old cruising infants participated. Among the participated infants, cruising experience ranged from 0.20 to 4.01 months, while crawling experience ranged from 0.46 to 5.19 months. Infants succeed in the handrail condition while failed in the floor condition. In the third study, four infants with age ranging from 10.88 to 11.44 months, who could take a few independent steps were enrolled. In the floor-gap condition, gap thresholds for these infants were comparable to those for cruisers. These infants who were taking steps differed from those who were sideways cruisers in their use of information for balance.
All three studies concluded that cruising may be common to hand and knee crawling rather than walking. The authors concluded that cruising and crawling may have a psychological function, which being the capacity of the infant to observe affordances for manual support. The study further concluded that crawling experience, just like cruising may fail to prepare an infant to notice affordances when they begin to walk. Transient skills such as cruising and crawling just represent a brief period of time in which infants find temporarily yet developmentally unique solutions.
Research study 2: Easily monitored markers of risk status2
Another research by Abubakar and colleagues was aimed at determining markers of risk status for identifying children in need of developmental intervention at an early stage. It aimed to develop an index that was used to identify such children. In this study, slow developmental achievements meant slow acquisition of development milestones. It was conducted in rural area of Kenya where 70 - 80% of children are born at home under the guidance of untrained traditional attendants. Undernourishment is endemic in this region. A total of ninety five children aged 2 to 10 months were made to participate in the study. Anthropometric measures were taken at every month’s visit; mother’s level of education was known; and all mothers were made to answer a locally developed checklist in the form of a questionnaire to assess their infant’s motor, language, and social development. All outcomes were predefined for the study. Upon completion of the study, a total of 14 children were classified as those experiencing a slow rate of development, 28.2% and 20% were stunted and underweight at the first time point, 31 mothers were unschooled, and the mean gravidity was 3.96.
Thus, this study showed that stunting, malnutrition, frequency, and severity of poor health in the child, and maternal factors such as mother’s low education and multiple pregnancies can be used to recognise children who are prone to a delay of developmental achievements (Abubakar, 2010). Based on these findings, the authors recommend that stunted children should receive highest priority in terms of interventions when resources are limited. Interventions aimed at improving physical development in early stage of life have the potential to improve outcomes. Growth monitoring programs should not only be limited to these factors but should expand to factors like monitoring fetal growth, which can be done by including maternal nutrition.
Research Study 3: Iron deficiency and infant motor development3
Iron deficiency in prenatal and perinatal life appears to impede the normal course of early motor development of the infant. During early developmental years, it impairs myelination and basal ganglia function. Through this study, Shafir et al determined the effects of iron deficiency without anemia (ID) and iron deficiency anemia (IDA) on infant motor skills that are linked to basal ganglia function and myelination (Shafir, 2008). This was an observational study on full term, healthy, singleton, 9 - 10 – month - old African-American infants. A total of 106 infants met the criteria for initial iron status classification, but only 77 did so for the final classification.
For gross motor outcomes, only 19% of the IDA infants and ID without anemia infants could stand alone, whereas 34% of iron sufficient infants could stand alone and 19% were already walking alone. On the PDMS-2 scale, scores for the ID without anemia group on the PDMS – 2 scale seemed to be intermediate between the IDA and iron sufficient groups, but the difference between ID without anemia and iron sufficient groups was not statistically significant. Iron sufficient group had the highest percentage of infants who had normal adult-like weight bearing while standing. ID infants, irrespective of anemia, performed poorly on the standing item compared to iron sufficient infants.
Thus, future interventions that comprise of infant’s motor training or other environmental improvement factors might help iron deficient infants to reduce long term poor effects.
Research study 4: Physical therapy in Down’s syndrome (DS) infants4
Down’s syndrome is one thing in which there is a delay in all of the developmental domains. A study by Ulrich and colleagues tested the effects of treadmill training on developmental outcomes in infants with DS since it is understood that DS infants are consistently late walkers. There is some amount of variability among children with DS with respect to the degree of disability and specific features. These children have delayed motor skills. DS children can sit without support by only 11 months of age, initiate standing position at about 17 months, and are able to take steps independently at an average age of 24 to 26 months. With systematic observations, Ulrich and colleagues hypothesized that treadmill can be a promising potential early intervention. The study sample included 30 infants with DS. For most infants intervention began at 10 months of age. The treadmill training was on infant-sized treadmill; 16 infants were randomly assigned to higher-intensity, individualized treadmill training (HI) group and 14 infants were assigned to the lower-intensity, generalized treadmill training (LG) group. In the LG group, the treadmill training included 8 minutes per day for 5 days every week at a belt speed of 0.15 m/s throughout the intervention. In order to progress the stepping performance of infants in the HI group, increased belt speed, ankle weights, and increase in regular period of training was done (Ulrich, 2008).
The results showed that the HI group gradually increased training conditions throughout, while the LG group kept a constant set of conditions (Ulrich, 2008). A the onset of training, infants in both the groups performed similarly, but by the end of last 2 quintiles, the infants in the HI group were performing and progressing faster as compared to those in the LG group. There were meaningful differences in six milestones in the HI group: moves forward; raises self to stand on both the feet; cruises; walks with support, walks without help, and walks without help with good co-ordination. From these observations, the authors learnt that treadmill training has proved to be efficient in decreasing the delay in the initiation of independent walking in DS infants. Infants in the HI group benefited from addition of weights to the ankles. Several other motor milestones were monitored throughout the study with no statistically significant differences between the HI and the LG group (Ulrich, 2008). This study confirmed the findings of several other published studies to prove that early intervention in the form of higher-intensity interventions may produce greater positive outcomes.
In conclusion, the authors reported that low - intensity treadmill training for DS infants resulted in an earlier beginning of walking and other locomotor milestones as compared to those who receive only exercise, but slowly increasing the strength of treadmill training can bring about greater increases in the amount of alternating steps, like in the HI group. The authors further advocate that clinics and hospitals should consider purchasing appropriate treadmills to rent out to parents of infants with DS.
Research study 5: Breastfeeding and developmental delay5
It is well known that breastfeeding is largely responsible for good health of an infant. If developmental delays are identified at the correct time, consequent problems like abnormal behaviour and long-term disability can be prevented. Many studies have investigated the potential role of breast milk on motor and cognitive development in early years of childhood (Sacker, 2006), but most of the studies are on highly selected groups like preterm born babies and low weight babies. Therefore, it there is no clarity if these results can be extrapolated to include the general child population (Sacker, 2006). This study has used data from the Millennium Cohort Study which was conducted on more than 18500 infants. The objective was to investigate if the duration of breastfeeding has an effect on the likelihood of gross and fine motor delay in infants. The study involved home visits by those taking interviews when the infant was 9 months of age on an average. Questions were asked regarding socioeconomic condition, household condition, adult-child interaction measures, and views on general health and development of the study infant. Breastfeeding was evaluated by asking “Did you ever try to breastfeed? From this question breastfeeding categories were derived like never breastfed, short duration (stopped early even before 2 months), intermediate duration (after 2 months and before 4 months), prolonged partial (even after 4 months with supplements) or prolonged exclusive (4 months or more with supplementary feeds at 4 months or later). The questionnaire tried to assess gross motor coordination and fine motor coordination. Generally, and for this study as well, the delay in the developmental milestones meant that the infant has not reached a milestone that 90% of singleton infants in that particular age group have reached. On the developmental delay, the authors assessed 3 sets of variables - biological, socioeconomic, and psychological as possible contributory factors.
The study showed that only 9% of full term and singleton infants were identified with delays in gross motor coordination, while 6% infants were identified with fine motor coordination delay. Very few (< 1%) showed problems with both gross motor and fine motor coordination. Sadly, 34% of MCS mothers did not breastfeed their infant at all, 47% of them initiated exclusive breastfeeding, but only 3.5% of infants were still being fed exclusively on breast milk after 4 months of age. The proportion of infants who mastered the developmental milestones increased with duration and exclusivity of breastfeeding. Infants who were never breastfed were 50% more likely to have gross motor coordination delay than infants who were breastfed for atleast 4 months (10.7% vs. 7.3%).
These results suggest that the protective effect of breast milk on gross motor skills of the child are due to some components of breast milk and is not a product of advantaged social position, parent’s education, or style of parenting. However, the association between breast milk and fine motor skills delay was explained by psychosocial, socioeconomic, and biological factors. Taking these findings into consideration, the authors support the need for policies that address socioeconomic circumstances and the necessity to encourage initiation and continuation of breastfeeding which will reduce the likelihood of developmental delay in the infant.
Research study 6: Maternal mental disorders and infant development6
Several studies have shown that maternal common mental disorders (CMD) like depression and anxiety disorders pose a serious health concern due to their adverse effect on infant development. As compared to children of mothers in good mental health, infants of mothers with CMD have been found to have a poor motor, cognitive, and socio-emotional development. According to a recent review, children most at risk of developmental deficits are children of mothers having a depressed mood throughout the child’s early years. In view of this, the authors of this study have aimed at investigating the effects of maternal CMD on child development outcomes and have explored the potential risk factors for child development. This study is a part of a large, population based cohort study from Ethiopia.
A total of 1065 pregnant women in their third trimester of pregnancy were made to participate in the study and followed up until their infants were a year old( Servili, 2010). The sample was restricted to 555 infants who could be weighed at birth. A sub-sample of infants who were weighed within 48 hours of birth was selected to determine developmental assessment, stratified by amount of exposure to maternal antenatal CMD symptoms. For assessment purpose, all infants (n = 68) exposed to high levels of antenatal CMD symptoms (≥ 6 on SRQ 20); those (n = 95) exposed to moderate CMD symptoms (SRQ score 2 to 5); and those (n = 95) exposed to low (SRQ 0 or 1) antenatal CMD symptoms, were selected.
Towards the end of the study, only 194 infants could be assessed due to exclusion of others due to various reasons. Developmental assessments could be completed for 65.3% of infants in the moderate CMD group and 81.1% in the low antenatal CMD group. When the infants were 12 months old, the prevalence of infants who were underweight was 21.6% whereas 45.5% of them were stunted. Only 7.3% of women had persistent perinatal CMD and 21.9% had CMD at either of the perinatal time points. A total of 70.8% mothers did not have CMD at either perinatal time points. The study failed to find any evidence of an independent effect of maternal CMD neither in pregnancy nor in the postnatal period upon infant development at 12 months of age (Servili, 2010). Moreover, the presence of persistent CMD was not significantly associated with infant developmental outcomes. However, low socioeconomic status and infant weight according to his/her age were independently associated with poor motor and cognitive development. Thus, authors conclude that it is not exposure to maternal CMD, but accumulation of risk exposures that affect the child development. Therefore, under nutrition, poverty, and interpersonal violence should be the targets to make sure the child reaches developmental milestones on time.
Thus, in all of these six research studies on achievement of developmental milestones in infants, the authors have tried to prove a common thing: there can be developmental delays in normal as well as mentally and physically challenged (e.g., Down’s syndrome) children, but prompt and timely interventions can either correct them or help reduce long term poor effects.
References:
- Adolph, KE., Berger, SE., Leo, AJ. (2011) Developmental Continuity? Crawling, Cruising, and Walking. Developmental Science, 14, 306 – 318. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3050596/pdf/nihms-215466.pdf
- Abubakar, A., Holding, P., Van de Vijver, F., Newton, C., Baar, A. (2010) Children at risk for developmental delay can be recognized by stunting, being underweight, ill health, little maternal schooling or high gravidity. Journal of Child Psychology and Psychiatry, 51, 652-659. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2919164/pdf/nihms212099.pdf
- Shafir, T., Angulo-Barrosa, R., Jing, Y., Angelili, M., Jacobson, S., Lozoff, B. (2008) Iron deficiency and infant motor development. Early Human Development, 84, 479 – 485 Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144491/
- Ulrich, D., Lloyd, M., Tiernan, CW., Looper, JE., Angulo-Barraso, RM. (2008) Effects of Intensity of Treadmill Training on Developmental Outcomes and Stepping in Infants with Down Syndrome: A Randomized Trial. Physical Therapy, 88, 114-122.
- Sacker, A., Quigley, M., Kelly, Y. (2006) Breastfeeding and Developmental Delay: Findings from the Millenium Cohort Study. Pediatrics, 118. Available at: http://pediatrics.aappublications.org/content/118/3/e682.full.pdf+html
- Servili, C., Medhin, G., Hanlon, C., et al. (2010) Maternal common mental disorders and infant development in Ethiopia: the P-MaMiE Birth Cohort. BMC Public Health, 10, 693. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091583/pdf/1471-2458-10-693.pdf
