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

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

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

Subjects: 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.

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

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

Conclusions: 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.