Women's Health (2013) 9(6), [569][570][571][572][573][574][575][576][577][578][579][580][581] support the demands of fetal growth. A progressive and marked insulin resistance develops in maternal skeletal muscle, beginning around mid-pregnancy and progressing during the third trimester to levels that approximate the insulin resistance seen in T2DM [9]. Hormones and adipo kines secreted from the placenta, including TNF-a, placental lactogen, placental growth hormone, cortisol and progesterone, are probable triggers of insulin resistance in pregnancy, owing to rapid reversal at delivery [10].Normal pregnancy is characterized by increased insulin secretion from pancreatic b cells to compensate for peripheral insulin resistance. This can be displayed as a hyperbolic relationship between insulin sensitivity (the inverse of insulin resistance) and insulin secretion from pancreatic b cells (Figure 2). The development of GDM occurs when a mother does not secrete enough insulin in order to be able to meet the metabolic stress of peripheral insulin resistance. The reciprocal relation ship is preserved in most GDM women, but occurs at much lower level of insulin secretion. That is, women with GDM secrete 40-70% less insulin for any degree of insulin resistance [11,12]. Therefore, pregnancy-induced insulin resistance may unmask the b-cell dysfunction characteristic of GDM [13].Serial assessments of insulin sensitivity starting before pregnancy have also demonstrated slightly greater insulin resistance persisting into the third trimester in women with GDM compared with normal pregnant women [11]. This resistance applies to both the action of insulin
Gestational diabetes mellitus & maternal obesityGestational diabetes mellitus (GDM) is the most common medical complication of pregnancy and is defined as glucose intolerance or high blood glucose concentrations (hyperglycemia), with onset or first recognition during pregnancy. The prevalence of GDM varies from 1 to 20% and is rising worldwide in line with increasing trends of maternal obesity and Type 2 diabetes mellitus (T2DM) [1,2]. The incidence of GDM rises disproportionately with increasing obesity. A recent meta-analysis of 20 population-based studies estimated that the risk of developing GDM is 2.14-fold higher for overweight (BMI: 25.0-29.9), 3.56-fold higher for obese (BMI: ≥30.0) and 8.56-fold higher for severely obese women (BMI: ≥40.0) compared with normal weight pregnant women (BMI: <25.0) [3]. Obesity and GDM have been recognized as independent risk factors for a number of adverse maternal and fetal outcomes, including diabetes, hypertension, operative deliveries, macrosomia and neonatal complications [4][5][6]. More recently, we have begun to understand that maternal obesity and GDM are also associated with significant lifelong consequences for the next generation [7,8]. As obesity and GDM share many of the same health consequences, obese women and their offspring are at a greater risk for adverse outcomes (Figure 1).
Pathophysiology of GDMDuring normal pregnancy,...