Small-for-gestational age Portuguese babies: the effect of childhood social environment, growth and adult socioeconomic conditions

INTRODUCTION:  This study aimed to assess how much of the differences in SGA (SGA) in terms of maternal social conditions and growth are reflecting childhood socioeconomic background.

METHODS: Adult women (n=6893) delivering single newborns at 5 public Portuguese maternities in Porto, Portugal, recruited as part of Generation XXI birth cohort were evaluated. Maternal education and marital status were used as adult socioeconomic indicators and grandparent’s education and social class (based on education and other resources) at the age of 12 years were used to characterize childhood social environment. Maternal height was used as proxy indicator of maternal growth and classified according the percentiles of the sample distribution (<10^th; 10^th-90^th; >90^th). The odds (and 95%CI) of SGA according adult socioeconomic indicators and height were estimated stratified by childhood conditions and adjusted for maternal age and gravidity.

RESULTS: SGA accounted for 14% of deliveries and was associated with lower maternal education (<12 years: OR=1.31 (1.13-1.51)), single marital status (1.57(1.16-2.13)) or living with a partner (1.22 (1.04-1.43)) and low maternal height (<10^th: 1.82 (1.49-2.21); >90^th: 0.52 (0.39-0.70)). No association was found between childhood social conditions and SGA. The effect of maternal high education was similar according childhood social class but the association of SGA with maternal height increased with increasing childhood social class. Marital status was not related with childhood conditions.

CONCLUSIONS: The effect of childhood social conditions was fully mediated by socioeconomic attainment and adult height and no independent association remained detectable. Although maternal educational attainment seems to be more important than the childhood background, the importance of maternal growth seems to be different according women’s trajectories.