Stillbirths more likely if diabetes in pregnancy not diagnosed

Pregnant women who develop the symptoms of diabetes in pregnancy (‘gestational diabetes’) but are not diagnosed are much more likely to experience stillbirth than women without the condition, according to a study published today in BJOG.

The study, led by researchers at the University of Leeds and University of Manchester, found that the risk of stillbirth was over four-times greater in women who develop symptoms  (raised blood glucose)  of gestational diabetes but are not diagnosed than in those without the condition. With appropriate screening and diagnosis, that excess risk, however, is eliminated.

Funded by Action Medical Research, Cure Kids and Sands, the study compared the symptoms and management of 291 women who had experienced a stillbirth in 41 maternity units in England to 733 similar women who did not experience a stillbirth. The study found that women in England with raised fasting plasma glucose (FPG) consistent with gestational diabetes still experienced – on average – twice the risk of stillbirth than women without the condition because many were missing out on diagnosis.

Dr Tomasina Stacey, who lead the study at the University of Leeds and now works at the University of Huddersfield explained; “There’s good news and there’s bad news. The good news is that women with gestational diabetes have no increase in stillbirth risk if the guidelines are followed for screening, diagnosis and management. The bad news is the guidelines are not always followed and some women, therefore, experience avoidably higher risk.”

The new research was published in BJOG: An International Journal of Obstetrics and Gynaecology.

The National Institute for Care Excellence (NICE) recommends that all women at a higher risk of gestational diabetes should receive blood screening for the condition; this includes women with a raised body mass index (BMI ≥30kg/m²) or from South Asian or Black Caribbean ethnic groups. Only 74.3% of the participating women with a raised BMI and 74.7% of the participating women from South Asian or Black Caribbean ethnic groups received screening. On average, women at higher risk of gestational diabetes who were not screened, as per the NICE guidelines, again experienced higher risks of stillbirth.

Professor Alex Heazell from the University of Manchester commented, “It’s not clear why some women missed out on being screened or diagnosed, but this needs to improve. Gestational diabetes can cause serious complications in pregnancy. It’s important that we detect every woman with symptoms so she can receive the appropriate care and support.”

In 2015, the NICE changed the threshold for diagnosing gestational diabetes from fasting plasma glucose to ≥5.6mmol/L; higher than the ≥5.1mmol/L threshold in the United States, and there is considerable debate worldwide about the appropriate level for diagnosis. The study, however, found little evidence to support one threshold over another, instead finding that the risk of stillbirth increased steadily with increasing glucose concentration.

Dr Stacey clarified; “There’s no level where the risk suddenly jumps. The choice of the right threshold for diagnosis is, therefore, more about pragmatism and finding the right balance of risk to resource; and avoiding over-medicalisation. Our study seems to support the current NICE guidelines, as long as they’re followed.”

The study is unique for separating the harmful biological effect of raised glucose from the beneficial effect of diagnosis which results in enhanced care and management. Dr Peter Tennant from the University of Leeds – and Fellow of the Alan Turing Institute – explained why this is so important; “There’s a lot of debate about the true impact of gestational diabetes, and whether it’s worth spending so much time and money on screening, diagnosis, and care. The existing research has shown only modest effects. But that’s in a world where we are – on the whole – providing good care. Only when you take that away and see what happens to women who aren’t appropriately screened or diagnosed, is the full impact clear.”