Do We Know How to Screen for Gestational Diabetes? Current Practice in One Regional Health Authority

To review current practice for screening and diagnosis of gestational diabetes (GDM) in the North East Thames health region, clinical directors and other relevant individuals in all 17 obstetric units within NE Thames were interviewed personally. Additional information was obtained from local midwives, diabetologists, and chemical pathologists. Thirteen centres had a formal policy for screening and diagnosis of GDM. One centre ran two policies. Six of 18 centres performed a routine blood glucose (BG) screen on all pregnant women, proceeding to OGTT either on the basis of raised BG alone (3 centres), or on the basis of raised BG and/or clinical risk factors (3 centres). Of the remainder, 10 performed a diagnostic test (OGTT or equivalent) in all those with risk factors, and 2 via an intermediate screening BG. The choice and interpretation of screening and diagnostic tests varied considerably. Six centres used random BG, with cut-off ranging from > 5.8 mmol I−1 to > 9.0 mmol I−1, one used a single fasting BG > 5.0 mmol I−1, and another a 50 g oral glucose challenge (1 h level > 8.0 mmol I−1). Diagnosis of GDM was based on a 75 g (13 centres) or a 50 g OGTT (2 centres), while 1 used a standard mixed meal, and another a timed post-prandial glucose sample. Timing of tests ranged from booking to 36 weeks gestation and the diagnostic cut-off levels for GDM varied (fasting: 5.0–8.0 mmol I−1; 2 h: 6.0–10.1 mmol I−1). There is no consensus concerning screening and diagnosis of GDM in the NE Thames region. This may reflect uncertainty about the value of screening for this condition.