The impact of revised diagnostic criteria on hospital trends in gestational diabetes mellitus rates in a high income country

Abstract

Objective: In 2010, national guidelines were published in Ireland recommending more sensitive criteria for the diagnosis of Gestational Diabetes Mellitus (GDM). The criteria were based on the 2008 Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) Study and were endorsed subsequently by the World Health Organization (WHO). Screening nationally is selective based on risk factors. We examined the impact of the new criteria on hospital trends nationally for GDM over the 10 years 2008-17.

Research design and methods: Data from three national databases, the Hospital Inpatient Enquiry System (HIPE), National Perinatal Reporting System (NPRS) and the Irish Maternity Indicator System (IMIS), were analyzed using descriptive statistics, analysis of variance, and Poisson loglinear modelling.

Results: The overall incidence of GDM nationally increased almost five-fold from 3.1% in 2008 to 14.8% in 2017 (p ≤ 0.001). The incidence varied widely across maternity units. In 2008, the incidence varied from 0.4 to 5.9% and in 2017 it varied from 1.9 to 29.4%. There were increased obstetric interventions among women with GDM over the decade, specifically women with GDM having increased cesarean sections (CS) and induction of labor (IOL) (p ≤ 0.001). These trends were significant in large and mid-sized maternity hospitals (p ≤ 0.001). The increase in GDM diagnosis could not be explained by an increase in maternal age nationally over the decade. The data did not include information on other risk factors such as obesity. The increased incidence in GDM diagnosis was accompanied by a decrease in high birthweight ≥ 4.5 kg nationally.

Conclusions: We found adoption of the new criteria for diagnosis of GDM resulted in a major increase in the incidence of GDM rates. Inter-hospital variations increased over the decade, which may be explained by variations in the implementation of the new national guidelines in different maternity units. It is likely to escalate further as compliance with national guidelines improves at all maternity hospitals, with implications for provision and configuration of maternity services. We observed trends that may indicate improvements for women and their offspring, but more research is required to understand patterns of guideline implementation across hospitals and to demonstrate how increased GDM diagnosis will improve clinical outcomes.

Keywords: Gestational diabetes mellitus; Oral glucose tolerance test; Pregnancy risk factors; Selective testing.

Fig. 1

Incidence of GDM nationally and at the 19 maternity hospitals*. * Hospital size based on total numbers of women delivered per annum. ‘New’ refers to the introduction of new national clinical guidelines in 2011. (Sources: Hospital In-Patient Enquiry System (HIPE) 2008–2017, National Perinatal Reporting System (NPRS) 2008–2013, Irish Maternity Indicator System (IMIS) 2014–2017)

Fig. 2

Average ages of all women giving birth (irrespective of parity) nationally and with/without GDM, 2008–2017. (Sources: Hospital In-Patient Enquiry System (HIPE) 2008–2017, National Perinatal Reporting System (NPRS) 2008–2016)

Fig. 3

Percentages of total live births with low (<2.5 kg) and high (≥4.5 kg) birthweight (BW), 2007–2016. (Source: National Perinatal Reporting System (NPRS) 2018)