August Cochrane review round-up
medwireNews: Three Cochrane reviews published in August covered the topic of diabetes during pregnancy, finding that more research is needed to guide the best strategy for detecting gestational diabetes and to establish whether preconception care is beneficial for women with type 1 or 2 diabetes.
In the first of two reviews focusing on gestational diabetes, Diane Farrar (Bradford Royal Infirmary, UK) and team analyzed the results of seven small trials from six countries comparing oral glucose tolerance tests with different methods of delivering glucose, including drinks, candy bars, and foods high in sugar.
None of the trials included in the review fully reported the methods used, and all had several aspects of unclear quality. The risk of bias was “generally unclear or high.”
Furthermore, none of the studies investigated the “important question of when is the best time during pregnancy to test women for [gestational diabetes], and none compared the standard [oral glucose tolerance test], which requires women to fast overnight, with a test that does not require an overnight fast,” report Farrar and colleagues.
Therefore, the team concludes that “studies in this review do not provide enough evidence to guide clinical practice and health policy regarding identifying women with [gestational diabetes].”
The second review, which included two trials involving a total of 4523 women and their babies, assessed whether screening for gestational diabetes based on risk profiles had an impact on maternal and infant outcomes, and whether there were benefits associated with screening in different healthcare settings.
Joanna Tieu (The University of Adelaide, South Australia) and colleagues found low-quality evidence from one trial to suggest that universal screening leads to more women being diagnosed with gestational diabetes compared with risk factor-based screening. In the latter, only women with at least one risk factor for gestational diabetes – such as having a first-degree relative with the condition, weighing more than 100 kg in the current pregnancy, and previous unexplained stillbirth – were screened. However, they note that the trial did not report on clinical outcomes for the mother or baby.
The other trial provided low- to very-low-quality evidence to suggest that screening for gestational diabetes in primary care was not associated with a difference in outcomes, including diagnosis of gestational diabetes, hypertension, preeclampsia, large for gestational age, and neonatal hypoglycemia, compared with screening in secondary care.
Based on these results, the researchers conclude that “[t]here is not enough evidence to guide us on effects of screening for [gestational diabetes] based on different risk profiles or settings on outcomes for women and their babies.”
The third Cochrane review, also led by Joanna Tieu, aimed to establish whether educational and supportive preconception care is beneficial for women with type 1 or type 2 diabetes who become pregnant.
Three randomized controlled trials addressing this question were identified, but none reported on the short- and long-term health outcomes for the mothers and their babies, leading the authors to conclude that there are insufficient data from randomized trials “to assess the effects of preconception care in women with diabetes […] or to support any particular protocol of preconception care over another.”
And the team recommends: “Future trials should be powered to evaluate effects on short- and long-term maternal and infant outcomes, and outcomes relating to the use and costs of health services.”
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