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Experts call for earlier screening of gestational diabetes

Screening should take place at 24 weeks, study suggests

Adrian O'Dowd

Friday, 08 April 2016

Screening for gestational diabetes in pregnant women could be taking place too late to help prevent babies from being born excessively large, concludes research* published today in the journal Diabetes Care.

Researchers from the University of Cambridge found that maternal obesity and diabetes in pregnancy too often resulted in early overgrowth of the baby in the womb.

Gestational diabetes can affect women during pregnancy, with those who are obese at greater risk. As well as affecting the mother’s health, the condition also causes the unborn child to grow larger, increasing the likelihood that her offspring will develop obesity and diabetes during later life. The condition can usually be controlled through a combination of diet and exercise or medication.

Women are screened for the condition through a blood glucose test at around 8-12 weeks into pregnancy and current guidelines in the UK recommend that mothers found to be at greatest risk should then be offered a full test at between 24 and 28 weeks into pregnancy. However, in practice the majority of women are screened at the 28-week mark.

Researchers at the Department of Obstetrics & Gynaecology at the University of Cambridge analysed data from the Pregnancy Outcome Prediction study, which followed more than 4,000 first time mothers using ultrasound scans to assess the growth of their babies in the womb.

They measured the abdominal and head circumference of the foetuses and compared the growth in women who developed gestational diabetes with those who did not.

Of the 4,069 women studied, 171 (4.2%) were diagnosed with gestational diabetes at or beyond 28 weeks. The researchers found no association between the size of the child at 20 weeks and the mother subsequently developing gestational diabetes.

However, they found that the foetuses of women subsequently diagnosed with gestational diabetes grew excessively prior to diagnosis, between 20 and 28 weeks.

Hence, the babies were already large at the time of diagnosis, and their findings suggest that the onset of foetal growth disorder in gestational diabetes predates the usual time of screening.

The researchers also studied women who were obese. Even in the absence of diabetes, the babies of obese women were also twice as likely to be big at 28 weeks.

The combination of obesity and gestational diabetes was associated with an almost 5-fold risk of excessive foetal growth by the 28 week scan.

Study first author, Dr Ulla Sovio, from the Department of Obstetrics and Gynaecology at the University of Cambridge, said: “Our study suggests that the babies of women subsequently diagnosed with gestational diabetes are already abnormally large by the time their mothers are tested for the disease.

“Given the risk of complications for both mother and child from gestational diabetes, our findings suggest that screening women earlier on in pregnancy may help improve the short and long-term outcomes for these women.”

Senior author Professor Gordon Smith, also from the University of Cambridge, added: “The evidence from our study indicates that there is an urgent need for trials to assess the effect of earlier screening, both on the outcome of the pregnancy and the long term health for the offspring.”

* Sovio U, et al. Accelerated Fetal Growth Prior to Diagnosis of Gestational Diabetes Mellitus: A Prospective Cohort Study of Nulliparous Women. Diabetes Care April 7, 2016. Published online before print April 7, 2016, doi: 10.2337/dc16-0160

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