Debate about treatment for gestational diabetes

Debate about treatment for gestational diabetes

When Sarah Tansky learned she was pregnant a second time, she was ecstatic. Her first pregnancy had gone smoothly: the baby, now a healthy two-year-old boy, grew exactly as expected and arrived in the world on his due date after a painful, yet largely unremarkable, labour.

So when she was told her baby wasn’t “measuring right” at the first dating scan, Tansky was shocked.

“My period had always been very regular, so I was confident about how far along I was,” the 25-year-old from Warwick, Queensland, tells Cosmos.

“But because bub was measuring very small, they pushed back my due date.”

A few weeks later Tansky returned for the 12-week scan, and this time, her baby was much bigger. Because normal foetal growth is a critical part of a healthy pregnancy and a major determinant of a baby’s long-term health outcomes, this irregular growth pattern began to concern her doctors.

At about 24 weeks, Tansky, like all pregnant women in Australia, was tested for gestational diabetes using a one-step test, which required her to fast overnight, then drink 100g of a sugar-laden drink, after which her blood glucose was measured via a blood test. It came back positive – just.

“I was just over the cut off – extremely borderline,” Tansky says. “But it meant I was still diagnosed with gestational diabetes, which changed the nature of my pregnancy.”

As a confirmed gestational diabetic, Tanksy was no longer able to give birth at her local hospital.

I was constantly being told that if diet and exercise didn’t get my readings down, I would need to get onto insulin.

Sarah Tansky

She was instead forced to drive an hour to the hospital in Toowoomba for regular checkups, in addition to receiving weekly calls from nurses and specialists informing her of the importance of diet, regular exercise and portion control.

“I’m not a big person; I started off my pregnancy weighing 55 kilos,” Tansky recalls. “And yet I was constantly being told that if diet and exercise didn’t get my readings down, I would need to get onto insulin.”

So she took even more walks (toddler in tow), cut out carbs, reduced her portion sizes. Despite this, her blood sugar readings continued to fluctuate and eventually she agreed to go on insulin.

“I’d been taking insulin for about 12 weeks when it showed that my baby’s weight had dipped below the 50th percentile. Before then, it has been at a steady, average weight,” Tansky says.

“I was not happy about this, and I asked a midwife if it was possible that the insulin could be stunting the baby’s growth. She said it was reasonable to assume that and that she would support me if I decided to get off the insulin. So I did.”

A black and white photo of a women with a baby.
Sarah and her daughter Frankie, who she was pregnant with when diagnosed with gestational diabetes. Credit: @reneemulcahyphotography

Tansky is in the middle of a hot debate about gestational diabetes in pregnancy. ​​It is now a common antenatal condition in pregnancy but mounting research is beginning to show that Australia may be getting it wrong with diagnosis and treatment, especially those who are borderline.

Paul Glasziou, Professor of Evidence-Based Practice at Bond University; Jenny Doust, Professor of Clinical Epidemiology at the University of Queensland, and women’s health consumer representative Leah Hardiman, who have worked closely with various Queensland health services, are calling on Australian clinicians to revise the way they diagnose gestational diabetes.

We want to change the process.

Professor Paul Glasziou

They argue that the current approach and guidelines are not only out of step with new evidence and with how other OECD nations diagnose and treat gestational diabetes, but also unnecessarily harming some women.

“We want to change the process,” Glasziou told Cosmos. “The current standard test – the oral glucose tolerance test – has poor reproducibility, meaning that repeating the test may give different results.”

The trio believes the thresholds used to define gestational diabetes is too low in Australia, and that these thresholds may be causing harm to women whose test results are borderline – like Tansky’s.

In Australia, a pregnant woman is usually tested for gestational diabetes between the 24 to 28 week mark via the glucose tolerance test.

Previously women were given the two-step test, which does not require them to fast overnight but instead drink 50g of sugar-laden water on the morning of the test, followed by a blood test to check glucose one hour later.

According to the current Australian medical guidelines – which are based on 2010 recommendations by expert body International Association of the Diabetes and Pregnancy Study Groups (IADPSG) – if the woman’s blood sugar levels read at or above 5.1mmol/L after fasting;  10.0mmol/L or above one hour after drinking a sugary drink; and 8.5mmol/L or above two hours after the drink, she is automatically diagnosed as having gestational diabetes.

This is where Glaszou, Doust and Hardiman think the overreach happens.

“Once a woman is diagnosed with gestational diabetes, she is identified as being a ‘high-risk’ pregnancy,” Glaszou says. “From this point on, there are changes in the model of care and the type of care delivered which can be very traumatising for many women.”

​​It is now the most common antenatal condition in pregnancy.

Chris Hegerty

In addition they believe that the unreliability of current glucose tests used in Australian needs to be addressed. A recent Australian trial of earlier testing in pregnancy found that one-third of women initially classified as having gestational diabetes (but neither told nor treated) did not have gestational diabetes when retested later in pregnancy.

Queensland doctor, Chris Hegerty from Warwick Hospital, believes that the increase in gestational diabetes diagnosis has resulted in little – if any – positive outcomes for women and babies, but has caused much harm.

“I remember that in the 1990s, gestational diabetes was a side issue with a diagnosis rate of about 3%,” he says.

“In the early 2000s it was about 4-5%, and since 2011, it’s taken off.

​​“It is now the most common antenatal condition in pregnancy.”

Hegerty says that women are being given misleading information and unrealistic expectations, including that treatment will prevent low blood sugars for babies after birth, breathing problems, feeding problems and long-term health problems.

Along with his colleague Dr Remo Ostini, Hegerty has recently published the first study to assess the effect ofincreasing gestational diabetes diagnosis on normal sized and small babies by comparing diagnosis rates, outcomes, interventions and medications between two periods: 2011- 2013 and 2016 – 2018, using perinatal data from Queensland.

“What we found instead was that even very small babies were having their growth restricted pharmacologically, and had a threefold increase in iatrogenic (caused by medical intervention) early birth, with possible adverse childhood neurodevelopmental effects,” Hegerty says.

The study found a woman ‘labelled’ with gestational diabetes was found to have an increased chance of having a caesarean section or induced labour, and only an 8% chance of spontaneous labour and vaginal delivery if taking Insulin.

“For at least 80% to 90% of babies who are not very large, there is no reasonable possibility of benefit from pharmacological treatment, and no conceivable reason to use drugs in these babies,” Hegerty tells Cosmos.

The University of Queensland’s Professor David McIntyre, a long-time endocrinologist, is critical of Hegerty and Ostini’s methodology.

“A more rigorous approach would have been to compare pregnancy outcomes in women with and without gestational diabetes, and then statistically correct for other obvious differences between the two groups (e.g. maternal BMI, age and parity) to make sure that the differences were actually due to gestational diabetes itself, rather than other unrelated factors,” McIntyre says.

However, he does agree with Hegerty that changes in maternal age, BMI and ethnicity are not enough to explain the increased frequency of gestational diabetes, and that the rise is more likely because of the increase in diagnostic testing.

Hegerty says the methodology used was the same as many other studies by “reputable researchers, some cited in our study, and including many Australian doctors and academics”.

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