Differences in mean performance IQ score at age 4 according to OME/HL group (up to 4 years).

aA negative coefficient indicates that IQ is lower in the OME/HL group compared to the unaffected reference group.bAdjusted for maternal education level, housing tenure, parental social class, maternal age, parity, smoking during 1st 3 months of pregnancy, smoking last 2 weeks of pregnancy, birthweight, gestational age, sex of child.cAdjusted for maternal education level, housing tenure, parental social class, maternal age, parity, smoking during 1st 3 months of pregnancy, smoking last 2 weeks of pregnancy, birthweight, gestational age, sex of child, home and parenting scores.dp-value for testing the effect of each OME/HL group vs the unaffected reference group.ep-value for linear trend in effect size across groups.