There was a significant difference in outcome of diabetic pregnancy between north east England and Norway. The risk difference was significant (p=0,0002) for the relative risk of perinatal mortality and was significant [p=0.0008] for relative risks of birth defect adjusted for maternal age.

Specific criticisms have been made of this work. One of the criticism is that in the north east England 1 in 335 pregnant women had diabetes yet in Norway 1 in 90 pregnant women were reported to have diabetes.