Babies’ health and medical threats for mothers can be improved by modifying the way that gestational diabetes is diagnosed, says new study.

The study involved 4,061 pregnant women in New Zealand and evaluated the significance of lowering the blood-sugar threshold for diagnosis.

The researchers, from the University of Auckland based at the Liggins Institute, tested the current blood-sugar level used in in Aotearoa New Zealand to diagnose gestational diabetes, a diabetes which can develop during pregnancy, and compared it to a lower level which is frequently used throughout the rest of the world.

Lead investigator, Professor Caroline Crowther, said: “Treatment for gestational diabetes improves mothers’ and babies’ health but it has been unclear what level of blood sugar should be used to make the diagnosis.”

The 4,061 women were randomised into two diagnostic groups, one using the lower blood-sugar level threshold and the other using the higher threshold. Of the women in the group which used the lower level, two times as many women were diagnosed with gestational diabetes. 15.3 per cent (310 of 2022) in this group were diagnosed, compared to 6.1 per cent (124 of 2039) in the higher threshold group.

The main aim of the study was to explore whether “the chance of having a baby born larger than expected for its gestation, which can cause complications during the birth,” said Science Daily. However, the researchers found that this did not differ between both groups.

The findings show that the mothers in the lower blood sugar group were more likely to undergo induced labour, receive pharmaceutical treatment for diabetes and use more health services. The babies born to these mothers had a higher chance of being treated for low blood sugar after birth (27.2 per cent compared to 9 per cent). It was suggested that this was due to these babies being closely monitored.

Professor Crowther explained: “These findings were driven by the differences seen in the 373 (9.2 per cent) of women with mild gestational diabetes who were diagnosed and treated for diabetes if they were assigned to the lower threshold group (n = 195) but who were not diagnosed and therefore not treated for diabetes if they were assigned to the higher threshold group (n = 178).”

The results stated: “Among the women in both groups who had glucose test results that fell between the lower and higher glycaemic criteria, those who were treated for gestational diabetes (195 women), as compared with those who were not (178 women), had maternal and infant health benefits, including fewer large-for-gestational-age infants.”

According to Science Daily: “A dangerous condition, pre-eclampsia, was less common in women in the diagnosed and treated group (0.5 per cent compared with 5.6 per cent).

“Birth of a baby born larger than expected for its gestation was reduced in the lower blood sugar group compared to the higher blood-sugar group (6.2% versus 18.0%). This was linked with a reduced risk of birth complications.”

“In the treated sub-group we found fewer occasions of shoulder dystocia, a birth complication where a baby’s wider than normal shoulders become stuck in the pelvis during the birth, than in the untreated sub-group (0.5% versus 3.9%),” added Professor Crowther.

Professor Frank Bloomfield, Liggins Director, said: “This research will help resolve the key lingering question over what diagnostic thresholds should be used for gestational diabetes.”

Following this study, the next step will involve following up with the mothers and children before they attend school to measure the effects on health and wellbeing of the two different diagnostic threshold groups later in life.

The research was published in The New England Journal of Medicine and funded by a grant from the New Zealand Health Research Council.

Another study is being led by Professor Crowther which analyses which blood sugar levels in mothers with gestational diabetes should be targeted to successfully control their blood sugar levels.

Editor’s note: Gro Health provides NHS-certified gestational diabetes support for women diagnosed with the condition. 

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