Lowering blood glucose cut-off values associated with reduced risk of large for gestational age: Study

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