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What Causes High Birth Weights in Newborns With Diabetic Moms?

by Sharon Perkins , studioD

If you have diabetes, your obstetrician might seem especially concerned about your baby's growth. That's because babies whose moms have diabetes often gain more weight in utero than other newborns. While having a big baby might not seem like a bad thing, large-for-gestational age infants have a higher incidence of health problems after birth and can also complicate labor and delivery. High glucose levels cause weight gain in babies with diabetic moms.

Diabetes in Pregnancy

If you have diabetes, you have more glucose in your blood than you need, because your body either doesn't make enough insulin to remove it or because your cells are resistant to the effects of insulin. Insulin helps cells remove glucose from your bloodstream. Pregnant women have one of three types of diabetes. An autoimmune disorder causes Type 1 diabetes, which usually develops at a young age. Type 2 diabetes accounts for around 90 percent of all diabetes cases, according to the International Diabetes Federation, and often affects overweight people. Around 18 percent of women develop gestational diabetes during pregnancy, because pregnancy increases your insulin requirements, the American Diabetes Association reports.

Effects on Your Baby

When you have high glucose levels in your blood, the excess amounts of glucose cross the placenta and reach your baby. Since the baby gets more glucose than he needs for growth, he makes extra insulin to remove it from his bloodstream. Because he can't produce enough insulin to remove all the excess, he stores some as fat. A baby that weighs more than 8 pounds, 13 ounces or 4,000 grams at birth has macrosomia, or excess weight at birth. Around 9 percent of all newborns fall into this category, according to MayoCinic.com. Between 15 and 45 percent of babies born to diabetic moms have macrosomia, obstetrician Vanessa Barss of Harvard Medical School reports.


Keeping your blood glucose levels within the limits your doctor sets will help prevent your baby from growing too large. To keep your blood sugars under control, you will probably need to take injectible insulin during pregnancy, even if you normally control Type 2 diabetes with diet. If you already take insulin, your insulin requirements may rise in the last three months of pregnancy. You will also need to watch your diet carefully and might see a diabetic counselor regularly to help. If your doctor estimates that your baby's weight will exceed 9 pounds, 14 ounces, he might suggest scheduling a Cesarean delivery.


Larger babies might have more difficulty getting through the birth canal. Around 25 percent of macrosomic babies develop shoulder dystocia during delivery, a condition where the baby's head passes through the birth canal but the shoulders get stuck, according to Dr. Barss. Both you and your baby can suffer serious complications from shoulder dystocia. After birth, the high levels of glucose in his blood suddenly drop, causing hypoglycemia, or low blood sugar. Babies of diabetic moms also have more breathing problems, because their lungs mature more slowly. Jaundice, calcium imbalances and heart problems also occur more frequently in macrosomic babies.

About the Author

A registered nurse with more than 25 years of experience in oncology, labor/delivery, neonatal intensive care, infertility and ophthalmology, Sharon Perkins has also coauthored and edited numerous health books for the Wiley "Dummies" series. Perkins also has extensive experience working in home health with medically fragile pediatric patients.

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