Hyperglycemia in pregnancy (HIP) is increasing in France, driven by changes in screening recommendations and shifts in maternal risk profiles, with direct implications for diagnosis and clinical management.

New data have shown that hyperglycemia detected in the first trimester is associated with adverse outcomes. However, uncertainty remains regarding the optimal diagnostic thresholds and timing of intervention. Emerging evidence suggests that early treatment may provide clinical benefits, although clinicians still lack clarity on which individuals to treat and when.

A French study using data from the French National Health Data System, including more than 8.1 million women without known preexisting diabetes who gave birth during this period, found that HIP prevalence increased from 7.5% in 2012 to 15.7% in 2022.

Screening Shift

Changes in screening recommendations account for approximately a quarter of the increase in cases of gestational hyperglycemia.

New screening guidelines were introduced in 2010. These recommendations advised fasting blood glucose testing in the first trimester of pregnancy for women with at least one risk factor, including maternal age ≥ 35 years, overweight or obesity, a family history of diabetes in first-degree relatives, a personal history of gestational diabetes, or macrosomia.

Hyperglycemia is defined using specific thresholds: ≥ 0.92 g/L (5.1 mmol/L) for gestational diabetes and ≥ 1.26 g/L (7 mmol/L) for type 2 diabetes, with confirmation required on two separate occasions.

In women without previously identified diabetes, whether gestational or type 2, an oral glucose tolerance test (OGTT) is recommended between 24 and 28 weeks of amenorrhea.

Changing Profile

The remaining increase reflects changes in the profile of pregnant women. In this study, 1 in 4 pregnancies occurred in women aged 35 years or older in 2022 compared with 19% in 2012. These later pregnancies were estimated to account for 20% of the increase in the prevalence of gestational hyperglycemia.

BMI has emerged as the main driver. Approximately 50% of the increase in prevalence was linked to rising BMI at the regional level, using the regional prevalence of preconception overweight to account for incomplete individual BMI data. In 2022, 29% of births occurred in regions where the prevalence of overweight before pregnancy exceeded 40% compared with 1.3% in 2012. By contrast, over the same period, the proportion of births in regions with a prevalence below 30% declined from 70.3% to 0.4%.

Threshold Limits

Although diagnosing and treating diabetes during pregnancy, whether gestational or type 2, is essential to reduce gestational and perinatal complications for both the woman and child, the current screening strategy has limitations.

The association between early hyperglycemia in the first trimester and subsequent gestational diabetes is inconsistent. Physiologic changes across pregnancy affect both blood glucose levels and insulin sensitivity. The fasting blood glucose threshold ≥ 0.92 g/L (5.1 mmol/L) was set arbitrarily, including by experts involved in developing the guidelines, and may be overly sensitive for identifying individuals who will progress to gestational diabetes.

Evidence suggests that there is no clear cutoff, with the risk for gestational diabetes increasing in a linear correlation with blood glucose levels. This association may extend to values within the normal range but close to the diagnostic threshold.

Several studies have shown that dysglycemia does not follow a fixed course. In a cohort study of 268 women with elevated fasting blood glucose levels in the first trimester, only half had gestational diabetes confirmed by the second-trimester OGTT. These findings were discussed in a 2017 French review.

Although early hyperglycemia is associated with adverse pregnancy outcomes and increased maternal and neonatal morbidity and mortality, early initiation of treatment is based more on pragmatic reasoning than on robust clinical evidence.

Recent evidence has begun to address this gap. In the TOBOGM randomized controlled trial, high-risk pregnant women with hyperglycemia detected in the first-trimester OGTT were randomly assigned to receive either immediate treatment or delayed treatment after repeat testing at 24-28 weeks of gestation if diabetes was confirmed.

Early intervention was associated with a statistically significant but modest reduction in the composite endpoint of major neonatal outcomes, including preterm birth before 37 weeks, birth weight ≥ 4500 g, neonatal respiratory distress, stillbirth or neonatal death, and shoulder dystocia.

Therefore, caution should be exercised. The researchers noted that treatment may be more beneficial for women with high blood glucose levels at early screening and may be more likely to harm those with lower levels, with a risk for low birth weight for gestational age observed during the pilot phase.

A large French study including nearly 700,000 births also showed that the timing of hyperglycemia diagnosis affects outcomes. Further research to define the optimal thresholds and timing for diagnosing gestational diabetes is ongoing.

This story was translated from Univadis France, part of the Medscape Professional Network.