The association between cord pH at birth and intellectual function in childhood

Acidemia at birth is very common but little is known about its long-term consequences.

To determine if pH at birth is related to established tests of intellectual function.

School children aged 6-8, for whom obstetric data were available, who had been delivered after labour at term, and had an umbilical cord arterial pH>7.00 (i.e. that was not extremely acidemic). STUDY DESIGN/OUTCOMES: Retrospective cohort study correlating birth and arterial pH data with childhood tests for non-verbal intelligence, grammar comprehension and literacy.

Relationships between pH and cognitive measures were analysed with parametric correlations. Partial correlations were used to examine these relationships, controlling for possible confounding factors.

Arterial pH was significantly negatively correlated with literacy (p=0.001) and with non-verbal intelligence (p=0.033).

Lower arterial pH is associated with higher scores on literacy and non-verbal intelligence tests at ages 6-8. This is unlikely to be a chance finding and is further evidence that acidemia in isolation should not be considered an adverse outcome. Further research on the relationship between labour and long-term cognitive measures is required.