Cute newborns are frequently associated with the physical attributes of being large and chubby. Onlookers can not help but notice these babies with so much fascination and utter words like, “What a healthy baby!” But are they really healthy?
Babies born greater than 4000 grams, or beyond the 90th percentile for gestational age, are called macrosomic babies. Macrosomia is a typical feature of infants of diabetic mothers. In other words, babies of diabetic mothers are expected to be considerably larger than usual. This happens because babies receive too much sugar via the placenta from their mothers who have high blood sugar levels. In an attempt to use up all the extra sugar, the baby will produce more insulin to break down the sugar and deposit it in the form of fat, making a large baby.
One fact holds true though: That infants of diabetic mothers are not as healthy as they might seem to be. Reports demonstrate that some of these infants have congenital anomalies. Two-thirds of the anomalies involve the cardiovascular and nervous system, with neural tube defects occurring 13-20 times more frequent than infants of non-diabetic mothers. Gastrointestinal, genitourinary, and skeletal anomalies are also common.
Macrosomic babies of diabetic mothers can also suffer from traumatic birth injuries such as clavicular fracture, shoulder dystocia, and brachial nerve injury resulting to inward turning of the shoulder. Birth injuries occur because these babies have a unique pattern of overgrowth. Their fats are centrally deposited in the interscapular and abdominal areas, giving them a bigger shoulder and larger extremity circumference and decreased head-to-shoulder ratio. A larger shoulder contributes to a difficult vaginal delivery, causing injuries.
Diabetic fetuses have also significant delay in lung maturity, making them at high risk for neonatal respiratory distress syndrome (RDS). Other known conditions associated with infants of diabetic mothers are hypoglycemia, hyperbilirubinemia, transient tachypnea (fast breathing), polycythemia (increased red blood cell volume), and hypocalcemia (low calcium). Furthermore, a growing body of research has also documented that by the age 10-16 years, children of diabetic mothers develop metabolic syndrome, which includes hypertension , childhood obesity, hyperlipidemia, and glucose intolerance. 
To prevent these complications from happening, good glycemic (blood sugar) control is crucial before and during pregnancy. Pre-pregnancy consult will identify women with preexisting diabetes so that they will be managed accordingly. Likewise, regular prenatal check-up should be done by any expectant mother so she can take advantage of the routine diabetic screening which is usually done at 24-28 weeks of gestation. This is done because a woman, even without a prior history of diabetes, can develop diabetes throughout the course of her pregnancy, known as Gestational Diabetes.
In the United States, approximately 3-10% of pregnancies are complicated by diabetes, 90% of which is gestational diabetes, and 8% is preexisting diabetes. 
Women whose diabetes are very well-controlled often carry their baby to term without any problems. The key to good glycemic control is to work closely with your obstetrician, internist, and dietician, who will provide you with the appropriate medications, regular blood sugar monitoring, and effective dietary plan.
1. Thomas R Moore, MD, et.al. (2007). Diabetes Mellitus and Pregnancy. http://www.emedicine.com/med/TOPIC3249.HTM