-Dr.Dianne McCallister, Chief Medical Officer at Porter Adventist Hospital

A Texas mom expected a big baby, but nothing like this: 16 pounds, 1 ounces.

Janet Johnson on Monday remained in an East Texas hospital after giving birth to what her doctors called one of the biggest newborns they've ever seen.

The normal weight for infants is between 6 pounds, 2 ounces and 9 pounds, 2 ounces. Only one in 1,000 babies is born weighing over 11 pounds.

What would cause a baby to be so large?

The most common cause of high birth weight babies is gestational diabetes. These are women who have normal blood sugar when not pregnant, but develop high blood sugar during pregnancy.

As a result of the mother having high blood sugar, the baby gets more blood sugar through the placenta. The baby's pancreas then makes extra insulin to help it maintain a normal blood sugar. The extra insulin stimulates the baby to grow larger than normal.

Babies from gestational diabetes have more health problems

• They can be born early due to their size or the mother's blood sugar levels
• Can injure a shoulder during birth
• Born with jaundice
• Develop Type 2 diabetes later in life

What causes gestational diabetes?

The answer is not really known. Many hormones that are produced by the placenta lower the effectiveness of insulin on lowering blood sugar. It is normal for pregnant women to have slightly higher blood sugars levels. However, in some pregnant women, the blood sugar is too high and affects the baby. This generally accurs in the last half of pregnancy.

How do physicians treat gestational diabetes?

OB doctors do many things during prenatal care that help to detect and prevent problems for the mother, and particularly for the baby.

Women who are planning on getting pregnant and have a high Body Mass Index - over 30 - or who have parents or siblings with diabetes - should be screened early in pregnancy for gestational diabetes

All women are checked between weeks 24 and 28 of pregnancy to make sure their blood sugar levels are not too high.

What can women do to prevent gestational diabetes?

There is no fool-proof way to prevent this problem, however, the following things help decrease your risks:
• Try to lose get down to a normal body weight before becoming pregnant..
• Stay active - exercise helps you maintain normal blood sugars
• Eat a healthy diet

Dr. McCallister is on 7NEWS at 11 a.m. every Wednesday. If you have a topic or question you would like her to discuss, email 11am@thedenverchannel.com.