Fetal Surveillance in Diabetic Pregnancies

Diabetes mellitus complicating pregnancy is one of the most common antenatal complications that are associated with significant perinatal mortality and morbidity (Magee et al., 1993; Platt et al., 2002; Schmidt et al., 2001). Diabetic pregnancies can be divided into two categories: those with pre-gestational or pre-existing diabetes mellitus in which the diagnosis is made in the pre-pregnancy state, and those with gestational diabetes mellitus (GDM). Pre-existing diabetes consists of type I (insulin-dependent) diabetes mellitus (IDDM)with an incidence of around 0.5%, and type 2 ( non-insulin-dependent) diabetes with an incidence of 2-3% ( Kapoor et al., 2007). The incidence of gestational diabetes mellitus differs in different populations (Gunton et al., 2001) and ethnic groups, and was shown to be as high as 13% in Chinese populations (Ko et al., 2002). Effective treatment of pre-existing as well as gestational diabetes mellitus was shown to improve outcome and reduce perinatal mortality, as compared to untreated patients (Lao et al., 2001; Langer et al., 2005). The pathological conditions encountered in fetuses of diabetic pregnancies differ in those with pre-existing diabetes mellitus and those with gestational diabetes. Pre-existing diabetics with persistent hyperglycaemia in the perinatal period are at higher risks of congenital malformations (Reece et al., 2007). In addition, those women with long-standing pre-existing diabetes before the index pregnancy run a higher risk of having diabetic vasculopathy that may affect various organ-systems in the body. Involvement of the uterine arteries will affect the development of an effective utero-placenta blood flow, which would be vital in maintaining normal growth and development in the fetus. The clinical manifestation of fetal growth restriction (also called intrauterine growth restriction) is thus more common in these pregnancies. The presence of significant congenital abnormalities and severe fetal growth restriction resulting from such conditions are logically directly related to increase in perinatal mortality and morbidity. On the other hand, gestational diabetes is usually only diagnosable either in a screening protocol or from clinical risk factors, by oral glucose tolerance test from mid trimester onwards, due to the effects of diabetogenic hormones from the placenta. The carbohydrate intolerance is thus short-lived and should last only from mid trimester to term. The hyperglycaemic states of the diabetes should revert to normal shortly after delivery with the removal of the placenta. Thus, chronic complications such as vasculopathy in the pregnant women will not have time to evolve during the course of pregnancy. On the contrary, the diabetic hyperglycaemic states