University of Otago preventive and social medicine researcher and study lead author Dr Andrew Sise said it was concerning because women with gestational diabetes were seven times more likely to develop type 2 diabetes, than those without.
Guidelines from the Ministry of Health recommend all women with gestational diabetes receive a blood test for type 2 diabetes at three months postpartum, then yearly.
Anonymous Ministry of Health National Collections data showed 14,443 women had gestational diabetes for the first time between 2005 and 2015.
However, of those women only 41% (5903) had a recommended test for type 2 diabetes within three months postpartum, 53% (7699) within six months and 61% (8814) within 12 months.
The study also revealed ethnic and regional disparities.
Only 35% of Maori women received a recommended test by six months postpartum, which was particularly concerning, Dr Sise said.
"The results of this study show that opportunities to protect the health of women with gestational diabetes through early detection and diagnosis of type 2 diabetes are being missed.
"The health system needs to ensure that women who have had gestational diabetes are appropriately followed up, and that type 2 diabetes screening is provided in a way that is accessible to them.
"Efforts to improve postpartum diabetes screening for women with gestational diabetes should look beyond just increasing screening overall, and ensure that it occurs fairly across all population groups.
"The large gap in screening between Maori women with gestational diabetes and women of other ethnic groups is especially concerning, and must be addressed."
Dr Sise was also "quite surprised" to find regional testing rates ranged from less than 20% in some areas of New Zealand, to more than 60% in others.
"It’s worrisome that if you lived in some places, you’d have had a very low chance of receiving a test. Ideally, everywhere would have a high rate of testing."
He said early detection of type 2 diabetes meant treatments could be put in place early to prevent or delay harm.
Left undiagnosed and untreated, type 2 diabetes could cause long-term health issues such as kidney disease, visual impairments, heart attacks, strokes, and problems with circulation.
