To the Editor: Dabadghao and colleagues have drawn attention to the high prevalence of diabetes mellitus and impaired glucose tolerance (IGT) among Australian women with polycystic ovary syndrome (PCOS).1 Quite rightly, both in this article and in the accompanying editorial by Teede and Stuckey,2 the authors have stressed the need to test women with PCOS for diabetes, and that long-term follow-up and lifestyle modification are important.

However, it is important to note that many of these women were attending a reproductive endocrinology clinic for treatment of infertility. Therefore, two other points need to be highlighted.

First, the high prevalence of glucose intolerance among this group is of immediate concern, as type 2 diabetes can pose a considerable risk to a pregnancy.3 The dangers include miscarriage, fetal malformation and perinatal mortality. Data from New Zealand indicate that perinatal mortality in pregnancies of women with type 2 diabetes was about triple that in pregnancies of women without diabetes; and, in women with type 2 diabetes which was not detected until after pregnancy was achieved, perinatal mortality was 4.5 times that of women without diabetes.4 Screening for diabetes therefore provides an opportunity to ensure that women with glucose intolerance are adequately prepared for pregnancy, thereby minimising the risks. Important measures include high-dose folate therapy and tight glycaemic control, in accordance with guidelines previously published in the Journal.5

Second, the risk of adverse pregnancy outcomes related to the women’s obesity (mean body mass index, 35.1 kg/m2) is also of concern. Therefore, stringent efforts should be made to take the opportunity presented to normalise the weight of women with PCOS before conception.6

The data presented by Dabadghao and colleagues also provide insights into the most appropriate means of screening for diabetes in this high-risk population. They have shown that screening by fasting glucose level alone will miss a third of cases of diabetes. Furthermore, at least 81% of IGT will also be missed! Glucose tolerance testing is therefore far superior to fasting glucose level for the detection of diabetes and IGT. This is a critical point, given the potential ramifications of undetected diabetes.

Given these findings, we urge clinicians to routinely perform a glucose tolerance test for women with PCOS attending for fertility treatment, so that all cases of abnormal glucose tolerance are detected, and appropriately managed, before and after conception. It would be a tragedy for a woman to achieve a pregnancy through in-vitro fertilisation, only to develop complications from undiagnosed diabetes.