Motor development is a set of change processes that take place throughout life, especially in childhood and adolescence . The same authors also consider that changes in movement and movement patterns change drastically during the first years of life, showing different rhythms of development from child to child, that is, a strong inter-individual variability and with differences from group to group.
Carvalho , says that at birth, all children are similar because they need care, progress according to a typical sequence of developmental stages, and learn appropriate social behaviors. However, the child becomes a unique being through socio-cultural influences, experiences and through its biological uniqueness . In this sense, society and culture can have a profound effect on an individual's motor behaviors mainly through the practice of physical activity, as well as socio-cultural elements, such as family, gender, race, religion and nationality, can guide the future of a child's motor behavior , increasingly suggests, the need to understand these elements, through a motor assessment, with specific tools and instruments.
Among the various specific motor assessment tools and instruments described in the literature (AIMS, GMFM, HINT, IB, MABC-II, MFM, PEDI, TGMD-2), a Peabody Developmental Motor Scales - second edition (PDMS-2)  is one of the most used instruments in clinical and research settings  just as it has the ability to be applied right from the birth of the child. This standardized tool was applied to assess the fine and gross motor skills of children, from birth to 71 months of age and its normative sample was based on 2003 children residing in forty-six states in the United States and in a province of Canada.
In its first edition , a PDMS was specially designed for the early detection of developmental delays or disturbances. The current revised version  has other advantages, which specifically allows: assessing the child's motor competence in relation to his peers; identify motor deficits and imbalances between the fine and gross motor domain; establish individual goals and objectives in clinical and / or educational intervention; and monitor the child's individual development. The same authors also highlight the usefulness of PDMS-2, as a research tool, proven with the use in several studies and research projects in the last decade.
The usefulness of PDMS-2 as an assessment tool is evident in several studies, which characterized the motor profile of special or clinical populations, such as: cerebral palsy, autism, Down syndrome and Hurler syndrome [7–11]. Nevertheless, PDMS-2 has been widely used to analyze the effects of biological (prematurity and malnutrition) and environmental (socioeconomic status, parents' educational qualifications, quality of the domestic environment, routines established by the family) on child development [12–23].
Its acceptance in the scientific community results from the fact that this instrument allows a multidimensional interpretation of motor behavior, through the calculation of the following motor composites: Gross Motor Quotient (GMQ), Fine Motor Quotient (FMQ), and the Total Motor Quotient (TMQ), what results from the first two. The segmentation of the TMQ has a very special interest for the differentiation of individual characteristics and, particularly, for the analysis of the effects of intervention programs .
According to Folio and Fewell , PDMS-2 is a significant improvement on the original version, with regard to the representativeness of the standards and their psychometric properties. In terms of instrument accuracy, the manual reports a good index of internal consistency for each subtest (α = .89 to .95) and for each motor quotient (.96 to .97), acceptable temporal stability, through the test-retest with an interval of one week (α = .73 to .96 depending on the age level) e high inter-observer fidelity, which varied between .97 to .99 for subtests and between .96 and .98 for the motor quotients. With regard to its construct validity, the two confirmatory factorial studies carried out, with two North American gauging sub-samples (up to 11 months and between 12 and 72 months) identified a measurement model, consisting of two factors - Fine Motor (FM) e Gross Motor (GM), defined respectively by two subtests of fine motor skills (Visual-Motor Integration and Grasping) and three gross motor skills subtests (Stationary, Locomotion, Object Manipulation, or Reflexes, in the case of children up to eleven months of age). In another study with Taiwanese children, developed by Chien e Bond , when specifically analyzing the dimensionality of the fine motor scale through the Rasch model (1960), concluded that the reduction of some items and the grouping of their two tests (Visual-Motor Integration and Grasping) would make the scale more consistent and more clinically useful. These results show that the validated measurement model, for the North American sample, may not be suitable or identical for another distinct population, so it is prudent to proceed with its cross-cultural adaptation before application . Regarding concurrent validity, the authors of the instrument  concluded that as PDMS-2, presenting a high correlation with its original version (α = .84 and .91 respectively for GMQ and FMQ) and with the Mullen Scales of Early Learning (Mullen, 1995) (α = .86 and .80 respectively for GMQ and FMQ).
Also Bean et al. , when assessing children at risk of development, aged between two and fifteen months, registered good rates of internal consistency (α = .90 and .97) between the results of three subtests (Reflexes, Stationary and Locomotion) the PDMS-2 gross motor scale and the total motor quotient of the Alberta Infant Motor Scale . In its turn, Connolly et al. , analyzed the concurrent validity between PDMS-2 and Bayley Scales of Infant Development II (BSID-II) with 12 month old children. The results showed a low correlation between the standard values of the motor quotients the PDMS-II and the Psychomotor Development Index of the BSID-II (α = .30; .22 and .32 respectively for GMQ, FMQ e TMQ). Only a high correlation was found in the values referring to age for the Locomotion test (α = .71, p < .05). Based on these results, Bean et al.  advise prudence in the interpretation of standardized values or values referring to age, when making clinical decisions based on a single assessment instrument..
The sensitivity of the instrument was confirmed by the authors of the scales , depending on age, sex, ethnicity (European Americans, African Americans and Hispanic Americans) and motor and mental deficits. Additionally, Wang, Liao and Hsieh , they also tried to test the sensitivity in a sample of children with cerebral palsy, aged between two and five years, the results suggest a sensitivity to developmental changes for an interval of six months. This appears to be an important improvement on the revised version, since Palisano et al.  had reported that the gross motor scale, of the original version of the PDMS, was not able to detect changes in the motor development of children with cerebral palsy, in an interval of six months.
Despite all the metric evidence, some authors [31–34] have warned that the application of PDMS-2, and particularly the interpretation of its standardized values, for certain special / clinical groups or in contexts culturally different from those for which the instrument was originally developed, should be developed with some caution, and recommend a cross-cultural adaptation and validation of the instrument to the population concerned. Regarding the reliability of the instrument for the Portuguese population, Saraiva et al. , reported in their adaptation and validation study, that most subtests had a good index of internal consistency (α = .76 to .95) and good test-retest stability (ICC = .85 to .95), concluding that the results indicate that the Portuguese version of PDMS-2 is an accurate and valid instrument for assessing the gross and fine motor skills of Portuguese children of pre-school age (from 36 to 72 months). However Saraiva et al.  refer that it is essential to replicate the same study, in different age groups, highlighting the age range from 0 to 36 months.
Thus, as an indicator and support for the assessment of motor skills by health and education professionals, it is pertinent to verify whether the PDMS-2 scales are suitable for the Portuguese population aged 12 to 48 months, so that it can be used as assessment instrument that allows to detect maladjustments, deficiencies or precociousness, and the child can later receive the appropriate intervention.
In this sense, the objective of the study was to analyze the psychometric properties of the Portuguese version of Peabody Developmental Motor Scales II (PDMS-2) for the Portuguese population from 12 to 48 months.
According to the existing literature, [3, 24, 35], it is expected that the Portuguese version of PDMS-2 will present psychometric properties similar to those of the original version in terms of its characterization, precision and theoretical construct, and that it will be an accurate and valid instrument to assess the gross and fine motor skills of Portuguese children aged 12 at 48 months.