Mother's educational level and foetal growth; the genesis of health inequalities
Résumé
Background: Women of low socioeconomic status (SES) give birth to lighter babies. It is unknown from which moment during pregnancy socioeconomic differences in foetal weight can be observed, whether low SES equally affects different foetal-growth components, nor what the effect of low SES is after taking into account mediating factors. Methods: In 3545 pregnant women participating in the Generation R Study, we studied the association of maternal educational level (high, mid-high, mid-low and low) as a measure of SES with foetal weight, head circumference, abdominal circumference and femur length. We did this before and after adjusting for potential mediators, including maternal height, pre-pregnancy BMI, and smoking. Results: In foetuses of low-educated women relative to those of high-educated women, foetal growth was slower, leading to a lower foetal weight that was observable from late pregnancy onwards. In these foetuses, growth of the head (-0.16 mm/week; 95% CI: -0.25,-0.07; p=0.0004), abdomen (-0.10 mm/week; 95% CI: -0.21,0.01; p=0.08) and femur (-0.03 mm/week; 95% CI: -0.05,-0.006; p=0.01) were all slower; from mid-pregnancy onwards, head circumference was smaller, and from late pregnancy onwards, femur length was also smaller. The negative effect of low education was greatest for head circumference (difference in standard-deviation score in late pregnancy: -0.26; 95% CI: -0.36,-0.15; p<0.0001). This effect persevered even after adjustment for the potential mediators (adjusted difference: -0.14; 95% CI: -0.25,-0.03; p=0.01). Conclusions: Low maternal education is associated with a slower foetal growth and this effect appears stronger for growth of the head than for other body parts.
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