4. Two randomized-controlled trials of routine ultrasonography screening during pregnancy were carried out, to see whether...

4. Two randomized-controlled trials of routine ultrasonography screening during pregnancy were carried out, to see whether routine ultrasound imaging influenced outcomes of pregnancy such as birthweight and mode of delivery. No significant differences were found. At ages 8 to 9 years, 2011 singleton children of the women who had taken part in these trials were followed up. Ultrasonography had actually been carried out on 92% of the ‘screened’ group and 5% of the control group. No significant differences were found in scores for reading, spelling, arithmetic or overall school performance. A subgroup of children underwent specific tests for dyslexia. The test results classified as dyslexic 21 of the 309 children in the screened group (7%, 95% confidence interval = 3-10%) and 26 of the 294 controls (9%, 95% CI = 4-12%]). (Lancet 1991; 339: 85-89.) a. What is meant by “randomized” and “controlled”? Why were these techniques used?

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