Low Birth Weight Babies


A baby is said to have low birth weight when he or she weighs less than 5 pounds, 8 ounces (2500 g) at birth. Low birth weight affects 1 in 14 babies born in the United States each year and can cause both immediate and long term problems. Low birth weight can occur in premature babies who are born before the 37th week of pregnancy (the normal length of pregnancy is 40 weeks) or in babies who are born at the regular time but are under weight (intrauterine growth restriction [IUGR]). IUGR can result from a variety of genetic, metabolic, and environmental influences.



  • Low birth weight premature babies are more likely to have underdeveloped lungs and breathing problems. Extremely premature babies (under 28 weeks) also can have heart problems that can lead to heart failure.

  • Very low birth weight babies (less than 3 pounds, 5 ounces or 1500 g at birth) can develop bleeding in the brain, leading to learning or behavioral problems later in life.

  • The liver may be immature and not function properly.

  • Anemia (too few red blood cells) or polycythemia (too many red blood cells) can also occur.

  • Often low birth weight babies do not have enough body fat and have trouble maintaining normal body temperature.

  • Feeding problems may occur, and risks of infection may be increased.



  • Have regular checkups through your pregnancy.

  • Eat a balanced diet high in fiber and low in fat.

  • Consume sufficient calories, vitamins and minerals, including at least 400 mcg of the B vitamin folic acid every day.

  • Gain a healthful amount of weight during pregnancy -- the recommended amount is 25 to 35 pounds.

  • Stop smoking and stay away from tobacco smoke during pregnancy.

  • Do not use alcohol or other drugs, including herbal preparations, unless they are prescribed by your doctor.


Although a serious and potentially life-threatening condition, low birth weight can often be treated. Your baby might have to stay in the hospital longer to be treated and until he or she gains sufficient weight. Medications can help correct or improve many low birth weight problems, and there are devices and medicines to help the baby breathe more easily during the critical early days of life.



  • National Institute of Child Health and Human Development, (800) 370-2943 or www.nih.gov

  • American Academy of Pediatrics, (847) 434-4000 or www.aap.org


Adapted with permission from JAMA Patient Page, January 2002 (not copyrighted).