In spite of advances in perinatal medicine, infants of diabetic mothers (IDM) continue to show increase morbidity and mortality [1]. Asymmetric septal hypertrophy (ASH) is a well-recognized cardiac functional abnormality in IDM. This term describes the special feature of the interventricular septum thickness >6 mm and septal/posterior wall thickness ratio >1.3 [2-4]. Its etiology is not clear, but endogenous catecholamines, insulin, and other growth factors have been involved [2], and its evolution is usually benign [2-4]. However, some cases of ASH and severe hypertrophic cardiomyopathy have been reported in spite of appropriate prenatal glucose control [5,6]. In Mexican macrosomic infants born to diabetic or non-diabetic mothers, ASH has been identified in 38.8% and 7.1%, respectively, though appropriate for gestational age (AGA) infants were not evaluated [4]. The aim of this study was to compare the frequency of ASH in AGA infants born to diabetic with non-diabetic mothers.

Diabetes mellitus was classified according to the ADA criteria [9], and good metabolic control was considered in case of glycosylated hemoglobin (HbA1C) levels <6% [10]. Signed consent was obtained from mothers to allow clinical chart review and ongoing echocardiographic evaluation. The study was approved by the local ethics committee.

TABLE I	Baseline Charaterstics of Appropriate for Gestational Age Infants Born to Diabetic and Non-diabetic Mothers  

IVS/PWLV, EFLV, DDLV and AoD were higher in IDMs than in INDMs, while TMD and TTD were lower (Table II). IVS did not show any relationship with HbA1C (r=0.02; P=0.87). ASH was not different in newborns born to mothers with HbA1C >6% vs. £6% (60.5% vs. 39.5%; P=0.08), respectively.

TABLE II	Echocardiographic Measurements in AGA Babies of Diabetic and Non-Diabetic Mothers

Three infants (7.9%) in the IDM group were detected with patent ductus arteriosus without any hemodynamic repercussions and hypoglycemia was detected in two patients (5.2%).

This study showed high ASH frequency in AGA IDMs. The IVS/PWLV index, DDLV and AoD were higher in infants with than in infants without ASH, while the EFLV was not different between groups. On the other hand, the TMD and TTD values were lower in IDMs than in INDMs.

ASH frequency in this study could be related to the poor metabolic control or just the interval of the disease prevalence. However, a limitation of the study is the convenience sampling and the historical control group. Furthermore, insulin levels were not measured either in the newborn or amniotic fluid, and some grade of hyperinsulinemia could still maintain glucose and glycosylated hemoglobin in control limits without general fetal macrosomia induction. It has been reported that adequate metabolic control especially in the third trimester, decreases ASH [11,12]. We do not know if the mechanisms　of ASH development are different from the development of large for gestational age infants, but recently Gordon, et al. [13], found that only transient hyperglycemic exposure is required to induce cardiac septal overgrowth in fetal rats, explaining why markers of chronic hyperglycemia often do not predict the degree of overgrowth. However, results require additional trans-lational studies. This could explain the lack of correlation between IVS size and Hb1Ac levels, also the association may be non-linear with a threshold effect and our sample size may be inadequate to show this effect. The IVS/PWLV index and DDLV higher in infants with than infants without ASH has been previously described [2,3,5]. However, it seems that IVS thickness was not enough to affect the left ventricle systolic function, except for obstructed left ventricle outflow as it has been pointed out [2].