Objective Women of low socioeconomic status (SES) give birth to babies with a lower birth weight. However, birth weight is a crude summary measure of fetal growth at the end of pregnancy, and it remains unclear how SES affects different fetal growth characteristics and leads to birth weight inequalities. We examined the association between maternal educational level as a measure of SES and three fetal growth characteristics.

Methods We studied this in 3545 pregnant women participating in a population-based cohort study. We used a questionnaire to establish level of maternal education (high, mid-high, mid-low and low). In mid and late pregnancy, ultrasound was used to measure fetal growth characteristics, ie, fetal head circumference, abdominal circumference and femur length.

Results In fetuses of women with low education relative to those of women with high education, growth of the head (−0.15 mm/week; 95% CI −0.24 to −0.07), abdomen (−0.09 mm/week; 95% CI −0.20 to 0.03) and femur (−0.02 mm/week; 95% CI −0.05 to −0.004) were all slower; from mid-pregnancy onwards, head circumference was significantly smaller and from late pregnancy onwards, abdominal circumference was also significantly smaller. The negative effect of low education was greatest for head circumference (difference in standard deviation score in late pregnancy −0.28; 95% CI −0.35 to −0.19). This effect remained statistically significant after adjustment for maternal age, parity, height, prepregnancy body mass index, smoking, single motherhood, whether the pregnancy was planned and financial difficulties (adjusted difference −0.14; 95% CI −0.25 to −0.03).

Conclusions A low maternal educational level negatively affects all three fetal growth characteristics, but predominantly the fetal head.