Outcome of pregnancy in diabetic womenBMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7286.614 (Published 10 March 2001) Cite this as: BMJ 2001;322:614
Authors did not define criterion for case selection
- Frank Johnstone, senior lecturer (firstname.lastname@example.org)
- Department of Obstetrics and Gynaecology, University of Edinburgh, Centre for Reproductive Biology, Edinburgh EH3 9ET
- Division of Child Health, University of Bristol, Bristol BS8 1TQ
- Northern Diabetic Pregnancy Survey, Regional Maternity Survey Office, Newcastle upon Tyne NE2 4AA
- Medical Birth Registry of Norway, Hauletend Hospital, N-5021 Bergen, Norway
EDITOR—Hawthorne et al claim to show that women with diabetes have a much more unfavourable outcome of pregnancy in England than Norway.1 But what does their study really show?
Their criterion for case selection (“diabetes”) was not defined. But the prevalence differs hugely between the countries: 1 in 335 pregnant women in northeast England and 1 in 90 in Norway were reported to have diabetes. This suggests that selection in the two countries was based on different clinical criteria. In northeast England most women included in the northern diabetic pregnancy survey were taking insulin before pregnancy, and all cases were confirmed by the clinicians and from the patient record.2 The data from Norway are from the centralised medical birth registry, and the possible pitfalls of this are illustrated by experience in Scotland.
I checked national registry listings of diabetes as part of the protocol for the SIGN (Scottish Intercollegiate Guidelines Network) guideline on management of pregnancy.3 Some women recorded as having diabetes did indeed have this, but some had only impaired glucose tolerance; some had had a glucose tolerance test but the result was normal; some …