Incidence, associated factors and influence of gestational diabetes on perinatal outcome before and after implementation of new WHO guidelines

Problem Statement: Gestational diabetes (GD) significantly contributes to perinatal mortality and morbidity and has an increasing prevalence worldwide. Ever since publication of the HAPO study in 2010, worldwide guidelines for diagnosis and management of GD are based on the recommendation of the International Association of the Diabetes in Pregnancy Study Group (IADPSG). Before that period, the majority of guidelines for GD diagnosis and management were based on the 1999 WHO criteria. The aim of this study was to determine the incidence, associated factors and influence of GD on perinatal outcome before and after implementation of new WHO guidelines. Methods: This is a cross sectional study performed using data from medical birth certificates collected in 2010 and 2014 in Croatia. The first group delivered in 2010 was selected as representative of pregnant women diagnosed and managed for GD using the 1999 WHO criteria where cut off values after intake of the 75g OGTT were: fasting glucose value 6.1 mmol/L and 2 hours glucose value 7.8 mmol/L. For comparison group we opted for year 2014 when all perinatal units in Croatia changed their guidelines to those defined by the IADPSG, where cut off values of the 75g OGTT are: fasting value 5.1 mmol/L, 1-hour value 10.0 mmol/L and 2-hour value of 8.5 mmol/L. Associated factors include age, height, weight before and at the end of pregnancy of pregnant women, while perinatal outcome was assessed by onset of labor, mode of delivery and Apgar score. All statistical analyses, including logistic regression (LR) analysis, were performed using STATISTICA ver. 12.0. Results: The study included 81.748 deliveries and 83.198 newborns. Prevalence of GD increased from 2.2% in 2010 to 4.7% in 2014. GD was shown to be a significant predictor of low Apgar score, labor induction and caesarean section in 2010, while in 2014 GD was predictive for labor induction and caesarean section, but not for low Apgar score. Age was predictive for labor induction only in 2014 and for caesarean section in both years, while BMI before pregnancy was predictive for all observed perinatal outcomes in both years. Conclusions: Prevalence of GD in Croatia has more than doubled from year 2010 to 2014, which is trend observed worldwide. Despite implementation of new diagnostic criteria and management guidelines, GD remains burdened with increased risk of labor induction and caesarean section, but no longer with low Apgar score. This may be influenced by several paramaters, but more precise and more strict diagnostic guidelines as well as management adjusted to these guidelines may be responsible for this observation. Further studies on management and outcome of pregancies burdered with GD are warrened to entirely understand the significance and impact of new diagnostic guidelines of GD. The study also showed that BMI remains an important predictor for all three perinatal outcomes. Thus, it is important to raise public awareness of appropriate weight management before and during pregnancy in order to improve antenatal care and perinatal outcomes.