Page 71 - Sample Moderate prematurity, socioeconomic status, and neurodevelopment in early childhood

compared with outcomes in MP boys, leaving out comparisons with full-term peers of the same gender. By doing so, the effects of gender were assessed instead of the gender-differential effects of moderate prematurity. Moreover, comparisons with other studies were limited because of variations in gestational age and age of assessment of developmental and behavioural outcomes.38, 46, 47 For a better comparison with our findings, larger cohorts of pre-school aged MP children are needed.
We also found that particularly preterm girls with low SES had poorer scores on externalizing and internalizing problems than girls overall. The prevalence rate of elevated total problems was 14% in MP girls with low SES compared to 4% in girls overall (Chapter 4). This may indicate that each additional neonatal or childhood adversity may have a multiplicative effect on girls’ emotions and behaviour. As such, low birth weight in combination with multiple socioeconomic adversities also has a greater effect on adolescent mental health than if only low birth weight were present.48 Nearly 100% of low birth weight girls with three or more adversities had depressive symptoms in adolescence.48 In summary, our findings are in agreement with the evidence that boys are more likely to have behavioural problems, but that girls, in particular, developed emotional and behavioural problems as a consequence of preterm birth and early socioeconomic adversity.
Explanations for gender differences
Previous research may provide some clues for explaining the gender differences we
found. In the first place, gender differences in vulnerability to neonatal and social
adversities may have their origins in foetal development. Evidence indicates that
boys and girls have a different physiological response to increased levels of stress
hormones.49, 50 A higher level of cortisol in pregnancy, as measure of maternal
stress, has only been associated with more affective problems in 7-year-old girls,
accounting for the effects of maternal depression during follow-up.49 Interestingly, 7 the association between high maternal cortisol levels and affective problems was
partly mediated by volume changes of the right-sided amygdala, a region of the brain involved in emotional functioning.49
Second, girls go through a more rapid process of cognitive and emotional development in the pre-school years than boys, and this may increase their vulnerability to emotional events and social-environmental adversities that influence normal development,51 such as lack of maternal warmth following
General discussion
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