Gestational diabetes. Screening, diagnosing, and consequences.

The aim of the thesis was to evaluate the effect of the different national and international screening methods of gestational diabetes (GDM) on the prevalence and maternal and neonatal outcomes of GDM pregnancies in Finland. GDM is defined as hyperglycaemia with onset or first recognition in pregnancy. In addition to adverse perinatal outcomes of the mother and newborn, it is also associated with long-term consequences, such as type II diabetes, metabolic disturbances and cardiovascular diseases. Although the impact of GDM on maternal and fetus health is well known, there is no consensus concerning its screening policy and diagnostic criteria.

In Finland, the recommendation on risk factor-¬based GDM screening was changed to comprehensive screening in 2008 when the first Current Care Guidelines (CCGs) on GDM were published. The aim of these guidelines was to standardise the screening method, diagnosis, treatment, and also prevention of GDM, as well as of type II diabetes mellitus and obesity.

One specific aim of the thesis was to evaluate the effect of the shift from risk factor-¬based to comprehensive screening on the prevalence and maternal and neonatal outcomes of GDM pregnancies in Finland. This shift led to a significant increase in the number of women with mild GDM who were more often primiparous, had a lower BMI and were less often treated with insulin. Comprehensive GDM screening led to decreased mean birth weight and macrosomia rates among newborns. Although the prevalence of neonatal hypoglycaemia increased, newborns required care in a neonatal ward less often, presumably due to their mild form of hypoglycaemia.

Another specific of the thesis was also to compare pregnancy outcomes according to International Association of Diabetes and Pregnancy Study Group (IADPSG) and National Institute for Health and Care Excellence (NICE) GDM criteria. We also explored the relationship between the number of abnormal values in the 2-hour oral glucose tolerance test (OGTT) and pregnancy and perinatal complications.

When comparing the IADPSG and NICE criteria, GDM prevalence was 2.4-fold higher according to the IADPSG criteria compared with the NICE criteria, but the macrosomia rate did not differ. Birth weight and the caesarean section rate increased already with mild, untreated hyperglycaemia. In the last paper which examined the significance of the number of abnormal OGTT (=how many of the three OGTT values exceeded screening threshold) values to pregnancy and perinatal outcomes, all women with GDM had an increased risk of delivery induction, regardless of the number of abnormal values, but the risk of caesarean section or macrosomia increased only after two or three abnormal values.

At the moment, already one fifth of pregnant mothers have GDM in Finland. In addition, the prevalence of the GDM is increasing with obesity and aging mothers. This places substantial demands on the health care system, what can be eased by implementing a uniform national policy to screen and treat GDM.