Birth weight is the first weight of your baby, taken just after being born. A low birth weight means that the baby is less than 5 pounds, 8 ounces. A high birth weight means that the baby is more than 8 pounds, 13 ounces.

A baby with a low birth weight can be born too small, too early (premature), or both. This can happen for many different reasons. They include:

• Health problems in the pregnant parent
• Taking certain medicines during pregnancy
• Substance use during pregnancy
• Infections during pregnancy
• Being pregnant with multiple babies
• Problems with the placenta, the organ that brings oxygen and nutrients to the baby
• Having small parents
• Genetic conditions in the baby
• Birth defects

Babies with low birth weight may be more at risk of certain health problems. They include immediate problems, such as:

• Breathing problems
• Infections
• Hypoglycemia (low blood sugar)
• Jaundice
• Trouble keeping warm

There is also a higher risk of longer-term problems, including:

• Delayed motor and social development
• Learning disabilities
• Certain health conditions as an adult, such as heart disease, high blood pressure, diabetes, and obesity

Causes of high birth weight can include:

• Having big parents
• Diabetes in the pregnant parent
• Certain genetic conditions
• Too much weight gain during pregnancy

High birth weight can be a concern because it can make delivery of the baby difficult and raise the risk of birth injuries. The baby is at higher risk of problems with:

• Blood sugar
• Breathing problems
• Jaundice

You may be able to prevent some birth weight problems by:

• Getting regular checkups during pregnancy
• Getting the right amount of nutrition and calories during pregnancy
• Controlling your blood sugar if you have diabetes
• Avoiding substance use during pregnancy