Lowering blood glucose cut-off values associated with reduced risk of large for gestational age: Study
Gestational diabetes mellitus (GDM) is a common maternal condition defined as the onset of hyperglycemia during pregnancy due to glucose intolerance. Increasing numbers of mothers with obesity and advanced maternal age have contributed to an escalating global prevalence of GDM. GDM is associated with various maternal and perinatal health risks, establishing it as a public health concern.
GDM diagnostic criteria and screening
In Sweden, maternal blood glucose is monitored during pregnancy when pregnant women visit the maternity clinic. If hyperglycemia is detected or clinical risk factors are present, an oral glucose tolerance test (OGTT) is conducted as a screening measure. The OGTT is typically performed between gestational weeks 24 and 28 or earlier in the presence of a substantial risk of underlying T2DM. In 2020, the Swedish guidelines for GDM were updated, and the 2013 recommendations from the World Health Organization (WHO) were implemented.
GDM diagnosis is based on plasma glucose levels meeting or exceeding specific criteria following a 75-g OGTT. These criteria include plasma glucose levels ≥5.1 mmol/L for fasting, ≥10.0 mmol/L for a 1- hour measurement, and/or ≥8.5 mmol/L for a 2-hour measurement. These cut-off values were determined based on data obtained from the HAPO study (The Hyperglycemia and Adverse Pregnancy Outcome Study), with a ≥75 % adjusted excess risk of adverse neonatal outcomes. Before the revision, a fasting value exceeding 7.0 mmol/L indicated GDM. The criteria for a 2-hour OGTT ranged from 9.0 to 11.1 mmol/L for capillary or venous samples.
GDM is a globally increasing problem associated with various maternal and perinatal complications. In Sweden, information is lacking regarding the impact of the incidence of LGA on reducing the blood glucose values required to diagnose GDM. Therefore, the study aimed to determine whether the change in diagnostic criteria impacted the incidence of LGA and resulted in the assessment of additional maternal and perinatal complications.
This retrospective cohort study involved 1237 women diagnosed with GDM. Among them, 92 delivered infants with LGA, 31 delivered infants small for gestational age (SGA), and 1111 delivered infants appropriate for gestational age (AGA). The primary outcome was to compare the incidence of LGA in the different cohorts based on the year they gave birth. Women without GDM at the same periods and their offspring were also analysed.
The incidence of LGA decreased following the change in diagnostic criteria for GDM (OR 0.43; CI 95 %, 0.27–0.68), a result that remained consistent after adjusting for known risk factors (aOR 0.44; CI 95 %, 0.27–0.7).
This study aimed to investigate the incidence of LGA and foetal and maternal outcomes following the change in diagnostic criteria. After changing the diagnostic criteria, the primary finding was a significantly reduced risk of LGA in women diagnosed with GDM. The incidence of LGA before and after the change in diagnostic criteria. The incidence of LGA is elevated in neonates born to mothers with GDM. This is a direct effect of maternal insulin resistance, resulting in maternal hyperglycaemia that induces foetal hyperinsulinemia, hyper glycaemia and overgrowth. The incidence of foetal macrosomia demonstrates a linear increase with rising levels of maternal hyperglycaemia. This study showed that neonates born to women diagnosed with GDM in 2021 and 2022 exhibited a significantly lower incidence of LGA(aOR 0.44) compared to those born to mothers diagnosed with GDM in 2017 and 2018.
This study aimed to determine the impact of lowered blood glucose cut-off values for diagnosing GDM on the incidence of newborns diagnosed with LGA. The results showed a reduced risk of LGA in neonate born to mothers who delivered after the change in the diagnostic criteria. This risk reduction remained after adjusting for risk factors and confounders. However, the comparison with non-GDM deliveries during the same period indicates that the results could be diluted, and the intervention may not have accounted for the lower incidence of LGA. A more plausible explanation could be the overall less severe forms of GDM after the change in diagnostic criteria. Despite this, the intervention seemed to impact foetal outcomes positively.
Source: E. Monemi et al.; European Journal of Obstetrics & Gynecology and Reproductive Biology 307 (2025) 43–48
