Editor—Gray et al 1 recently reported an apparently new observation that “maternal hypertension has a protective effect against cerebral palsy in very preterm infants.” Do their data support this conclusion, which is different from the conclusion reached by two other case control studies2 3 on this topic?

In the same issue, Tin et al 4remind us that those infants who are difficult to follow up have different (worse) outcomes than those infants who could be followed up without great difficulty. They provide a key message that “studies where it is not possible to see some children for assessment might usefully include a calculation of what the total prevalence would be if there was a fivefold difference in the proportion with the condition in question among the children who were not seen.”

Gray et al’s study comprised 107 in the study group, of whom there were 101 survivors. At 2 years of age, four in the study group were lost to follow up …