Читать книгу Gestational Diabetes - Группа авторов - Страница 35

On a worldwide scale, the prevalence of obesity has clearly increased markedly in recent decades, and women of childbearing age are certainly part of this global phenomenon [3]. In high-income countries, this primarily represents a shift toward increasing obesity across the population with higher prevalences and ongoing increases noted among women [4]. In the USA, for example, 37% of women aged 20–39 are currently obese [4]. Even in high-income countries, variations within populations persist, for example, related to urbanization [5]. In low- to middle-income countries, the situation is more complex, with varying degrees of undernutrition, growth stunting (with reduced stature), and overnutrition frequently coexisting within the same community or even the same household [6].

Well-recognized consequences of maternal obesity in the pregnancy context include relative infertility, increased rates of miscarriage and stillbirth, increased risk of congenital anomalies, higher rates of excess fetal growth and consequent obstructed labor, increased risk of hyperglycemia in pregnancy, increased risk of hypertensive disorders of pregnancy, and higher risk of postpartum hemorrhage [3].

Many reports have attempted to dissect the relative clinical and population health importance of obesity and hyperglycemia relating both to their effects on pregnancy outcomes and later maternal and infant health. Separation of their associations is difficult, especially as the 2 conditions frequently coexist and obesity lies on the causal pathway toward hyperglycemia. Furthermore, heterogeneity in study populations, screening protocols for hyperglycemia, treatment directed at correction of hyperglycemia, and methods of analysis complicate the interpretation of studies [7–10].

More recently, many of these methodological issues have been addressed by the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study [11, 12], in which caregivers were blinded to the results of a 75 g OGTT performed on average at 28 weeks gestation unless the levels fell above predefined thresholds leading to the subjects being excluded from the study. In addition, no specific intervention was provided for hyperglycemia or obesity in the HAPO cohort. The HAPO study demonstrated that the associations of increasing maternal BMI and hyperglycemia with pregnancy outcomes were similar. Both were associated with increased rates of large for gestational age (LGA) babies, primary cesarean section, clinical neonatal hypoglycemia, and neonatal hyperinsulinemia and important secondary outcomes including fetal adiposity and preeclampsia. In general, the association of maternal BMI with these outcomes tended to “plateau” in the highest categories, whereas that of glucose was still increasing [13].

The combined associations of BMI and gestational diabetes mellitus (GDM) with adverse pregnancy outcomes have also been reported [12]: across the HAPO study, obesity was present in 13.7% and GDM by International Association of Diabetes In Pregnancy Study Groups (IADPSG) criteria [14] in 16.1% of those who remained blinded. Only 25% of the women with GDM were obese. Compared to women with neither GDM nor obesity, the adjusted ORs for most pregnancy complications were increased both in women with obesity alone and in those with GDM alone. Preeclampsia appeared to be more prevalent in the “obesity-alone group,” whereas excess fetal growth and fetal hyperinsulinemia were slightly more common in the “GDM-alone group” than in the “obesity-alone group.” The combination of GDM and obesity was clearly associated with a marked increase in the risk of pregnancy complications.

Some other studies also help to separate the roles of obesity and GDM in determining adverse pregnancy outcomes. In a case – control cohort from the USA, untreated lean women with essentially untreated GDM (women with very little to no prenatal care who were diagnosed with GDM at >37 weeks gestation) had a 2-fold higher risk of the composite outcome of stillbirth, neonatal macrosomia-LGA, neonatal hypoglycemia, erythrocytosis, and hyperbilrubinemia and a 7-fold increase in metabolic complications [15]. These increases in adverse outcomes were similar to those in obese women without GDM. Untreated lean women with GDM also had higher rates of induction of labor and delivery by cesarean section than lean women without GDM. For obese untreated women with GDM, these risks were increased for the composite outcome (by 10-fold); LGA infants (3-fold); metabolic complications (5-fold); induction of labor (4-fold); and delivery by cesarean section (9-fold). These results suggest that obesity and GDM individually are associated with adverse outcomes but that their combined occurrence significantly increases the risks. However, when treated for GDM, the risks for adverse pregnancy outcomes were reported not to be higher for obese women in general [16] or obese women treated with insulin but not diet [17].

Thus, there is evidence to demonstrate that maternal BMI and glycemia have independent and essentially additive associations with adverse pregnancy outcomes. In view of this, the relative “importance” of these factors is heavily influenced by the potential costs and benefits of preventative or treatment strategies.