Should Glycemic Targets for Gestational Diabetes Be Changed?

Alessia De Chiara

September 29, 2022

Use of tighter glycemic targets for women with gestational diabetes mellitus (GDM) reduced the risk for a serious health outcome for the infant, according to a trial conducted in New Zealand. These serious health outcomes included death, birth trauma, and shoulder dystocia. Infants' length of stay in the neonatal intensive care unit also was shorter. But the new targets did not reduce the infant's risk of being large for its gestational age.

For the women, there was an increase in the risk for serious health outcomes, including postpartum hemorrhage, and an increased use of pharmacologic therapy to treat their hyperglycemia. These findings were reported in a recent article in PLOS Medicine.

The optimal glycemic targets for women with GDM remain unclear, and clinical practice guideline recommendations on the glycemic targets for these women vary worldwide. "Treatment for GDM aims to reduce maternal hyperglycemia, although it remains uncertain how tight glycemic control should be to minimize maternal and perinatal risks," the researchers wrote.

In 2014, New Zealand's Ministry of Health published updated GDM guidelines that recommended the adoption of tighter glycemic targets than those that had been in place since 1998. Targets for fasting glucose changed from < 5.5 mmol/L (< 99 mg/dL) to ≤ 5.0 mmol/L (≤ 90 mg/dL). The 1-hour postprandial target changed from < 8.0 mmol/L (< 144 mg/dL) to ≤ 7.4 mmol/L (≤ 133 mg/dL), and the 2-hour postprandial target changed from < 7.0 mmol/L (< 126 mg/dL) to ≤ 6.7 mmol/L (≤ 121 mg/dL).

As mentioned in the PLOS Medicine report, the TARGET trial was conducted at 10 maternity hospitals in New Zealand between May 2015 and November 2017. A total of 1100 women diagnosed with GDM at 22 to 34 weeks' gestation were enrolled, along with their 1108 infants. Every 4 months, two hospitals moved from using less stringent targets to tighter targets. Overall, 598 (55%) women (602 infants) were included while their hospital was allocated to the use of tighter targets, and 502 (45%) women (506 infants) were included while their hospital was allocated to the use of less stringent targets.

The incidence of large for gestational age — defined as birth weight >90th percentile using growth charts adjusted for gestational age and infant sex — was the primary outcome measure. The rate was similar between the treatment target groups, occurring in 14.7% of the infants in the tighter target group and in 15.1% of the infants in the less stringent target group.

The composite serious health outcome for the infant of perinatal death, birth trauma (eg, nerve palsy, bone fracture), or shoulder dystocia was apparently reduced in the tighter group when adjusted for gestational age at diagnosis of GDM, maternal BMI, ethnicity, and history of GDM, compared with the less stringent group (adjusted relative risk [aRR], 0.23; P = .032). In addition, the length of stay in intensive care was shorter for infants whose mother had been in the tighter glycemic target group. Apart from that, no differences were seen for the other infant secondary outcomes.

Secondary outcomes for the women showed an apparent increase for the composite serious health outcomes that included major hemorrhage, coagulopathy, embolism, and obstetric complications in the tighter group (aRR, 2.29; P = .020). Women in the tighter target group (67.9%), compared with women in the less stringent target group (58.5%), were more likely to require pharmacologic treatment for glycemic control (aRR, 1.20; P = .047).

As the researchers concluded, these findings have direct relevance for clinical practice and can be used to aid decisions on the choice of treatment targets to use when discussing glycemic control for women with GDM. Nevertheless, they pointed out, there is a need to confirm their findings by other randomized trials and in different healthcare settings.

This article was translated from Univadis Italy.

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