Page 75 - Sample Moderate prematurity, socioeconomic status, and neurodevelopment in early childhood

occupational level of the mother, and occupational level of the father. All five indicators were available for the majority of the participants. For some participants, however, data on one of the indicators was missing, in particular family income or the occupational level of the mother. The composite SES was measured using the available indicators. Since data on educational level of both parents was most complete, it is likely that these two indicators weighed somewhat heavier in the overall effect of SES than the other indicators.
Data on SES indicators were collected at different points in time. In a general questionnaire, parents were asked to fill in their highest completed educational level and the net monthly family income shortly before the scheduled PCH visit at four years of age. Data on occupational level, however, were collected retrospectively from the medical birth registers kept by the PCH centres. It is possible that the occupational level of the parents had changed between birth and four years later, for example, due to losing a job or obtaining a higher position. In this way, changes in occupational level could have led to positive or negative deviations regarding the effect on neurodevelopmental problems. For the same reason, the family income when the child was four years old may not fully represent the level of income from birth up to four years of age. It is likely that the composite SES gives a better impression of the SES from birth up to four years than each of the indicators alone.
Assessment of neurodevelopmental outcomes
We used parental questionnaires to assess developmental delay and behavioural and emotional problems. Parental reports have proven to be valid when it comes to signalling psychosocial problems in preventive child healthcare.74 Nevertheless, additional testing by medical specialists or psychologists would have had added value, in the sense of providing a professional view on developmental and behavioural problems of the children in the LOLLIPOP study.
Using the ASQ as a screening instrument for measuring developmental
delay has both advantages and disadvantages. The ASQ is a reliable and valid 7 questionnaire for developmental screening, also in preterm children.75-77 Practical
advantages are that the ASQ is cheap and, generally, completed quickly. Most
parents consider the questionnaire easy to fill in78 and 97% can do so without the
help of others.79 Nevertheless, in the LOLLIPOP study not all ASQ domain scores
were completely filled in by all the parents, which indicates that some parents may
have had difficulties in comprehending the questions.80 For example, the 25 (9.9%)
of the low SES mothers who originated from non-European countries may have
General discussion
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