Parentpedia

What Experts Say^*

Every parent-to-be hopes for a healthy baby, and a newborn's weight is an excellent indicator of it. That's why health professionals involved with all aspects of pregnancy and birth seem to be so focused on the baby's weight.

The fact is, babies born at a low birth weight -- defined as less than 5 lbs., 8 oz. -- may be vulnerable to a host of health problems, even as advances in neonatal care improve the lives of countless tiny newborns.

What Is It?

Today, about one in every 13 babies is born at a low birth weight. According to the March of Dimes, low-birth-weight babies fall into two broad categories:

• premature (born before 37 weeks gestation)
• small-for-date, who are full-term but, for a variety of reasons, are underweight. Some small-for-date babies are just naturally small, while others have birth defects or had growth problems in utero. Twins and other multiples are also more likely to be born at a low birth weight.

Causes of Low Birth Weight

Factors that lead to slow uterine growth include:

• maternal smoking
• drug or alcohol abuse
• a chronic maternal health problem such as high blood pressure
• various infections, either yours or the baby's
• placental problems (the placement of the placenta may impede the flow of blood and nutrients to the baby)
• low maternal weight gain
• other factors, such as socioeconomic status (low income and education level seem to affect a baby's birth weight, though the reasons are unclear), and even age (babies born to teen mothers are more likely to be underweight)

Potential Complications

Low-birth-weight babies may have problems with:

• Breathing. Low birth weight and underdeveloped lungs make it more likely that premature infants may need breathing assistance.
• Brain Bleeding. Very low birth weight babies (less than 3 lbs., 5 oz.) may experience bleeding in the brain, which can in extreme cases (though not always) lead to brain damage or later learning problems.
• Feeding Issues. Smaller babies tend to be weaker, and may have trouble sucking and/or swallowing. Plus, without the layer of body fat larger infants have, smaller newborns have trouble regulating their body temperature.

Preventing Low Birth Weight

Be sure to eat a balanced diet when you're pregnant, and aim to gain the proper amount of weight. According to the American College of Obstetricians and Gynecologists, that's 25-35 lbs. for normal-weight women, 28-40 lbs. for underweight women, and 15-25 lbs. for overweight women.

Also, talk to your doctor about how much folic acid you should be taking. It's been shown to reduce birth defects, which are another cause of low birth weight.

If you smoke, stop. Smoking during pregnancy has been shown definitively linked to low birth weight, says a 2005 study at the University of Vermont.