Metformin is an underutilised treatment option for gestational diabetes mellitus (GDM) in Australia, NSW clinicians say.
According to a multidisciplinary team from the Illawarra Health and Medical Research Institute, metformin is commonly used in pregnancy overseas and has advantages such as patient preference for an oral therapy.
However in Australia, insulin was considered the gold standard for treatment when medical nutrition therapy was insufficient to achieve glycaemic targets.
“Though insulin is currently first line as the only approved pharmacological intervention in pregnancy in Australia, metformin could play an important role in improving care and treatment outcomes for women with GDM,” the Opinion article said.
Writing in the Australian and New Zealand Journal of Obstetric and Gynaecology, they said metformin had been shown to improve perinatal outcomes in terms of prevention of macrosomia, severe neonatal hypoglycaemia, maternal hypoglycaemia, lower postprandial readings, gestational weight gain (GWG), pre-eclampsia and gestational hypertension, compared to insulin.
“Furthermore, metformin also requires less monitoring in pregnancy and has patient preference over insulin, even though a small portion of women may experience gastrointestinal side effects and up to 20–50% women may need some supplemental insulin.”
They said even in women requiring supplemental insulin, metformin would still be beneficial in reducing total insulin requirements in pregnancy, potentially preventing additional weight gain and reducing the risk of maternal and neonatal hypoglycaemia.
“For an individualised treatment approach in GDM, women with higher pre-pregnancy BMI or excessive GWG may benefit from a combination of metformin and supplemental insulin to alleviate insulin resistance and further weight gain, whereas women with normal BMI and GWG may benefit from focusing on diet and insulin therapy to reduce adverse pregnancy outcomes.”
The authors, led by clinical nurse specialist and diabetes educator Ms Beenu Bastian, said metformin was safe for use in pregnancy.
“The cautionary approach to the use of metformin in pregnancy and clinician inertia in Australia, despite its common use in pregnancy overseas, is due to cross-placental transfer and lack of long-term safety data.”
“We believe it is time for the safety of metformin to be reassessed by the Therapeutic Goods Administration as a matter of priority with a view to providing other treatments for GDM that can reduce poor obstetric and neonatal outcomes.”
They said the choice of metformin and insulin to treat GDM could be based on the assessment of variables such as maternal BMI, fetal growth measurements, GWG in addition to cost effectiveness, tolerance to the medication and patient preference.
“The clinician inertia for treatment intensification can be addressed through more evidence-based resources and education. Patients should also be encouraged to make informed choices about their treatment options for managing GDM to enhance acceptance, compliance and empowerment, which may in turn positively impact their outlook on health, quality of life and future risk of diabetes.”