Low Birth Weight

When a baby is born weighing less than 2,500 grams (5 lbs, 8 ounces) he or she is considered to have a low birth weight. In some cases, babies born prematurely or with intrauterine growth restrictions (two leading causes of low birth weight – see below) may see an increase in risks for complications such as mental retardation, vision loss, and/or learning problems. Currently, about one in twelve babies are born with a low birth weight. However, that number has greatly decreased due to advancements made in prenatal care.

It’s important to know that not all babies born with a low birth weight have a condition or problem. Some babies are just born small. In these cases, it is not abnormal and not a cause for concern. Doctors may expect a baby with low birth weight if the mother’s uterus is small, if she has a small frame, or if the ultrasound shows the baby is smaller than normal.

Low Birth Weight Causes

The two main causes for a baby to be born at a low birth weight are premature birth and intrauterine growth restrictions (IUGR). Premature birth is a term for a baby born before 37 weeks of pregnancy. Sixty-seven percent of all low birth weight babies are premature births. Many people refer to these newborns as “preemies”. The earlier the baby is born, the less he or she will weigh. Babies born weighing under 3 pounds, 5 ounces are at extremely high risk for health problems at the moment of birth, in the days and weeks after birth, and during their lifetime. Premature babies born closer to term tend to need supervision for a few days, but are statistically in good shape, with mild or no health problems. However, late preterm infants have a significantly higher mortality rate than term infants and may be deceptively well looking.

Intrauterine growth restriction babies are also known as growth-restricted, small-for-gestational age, or small-for-date babies. Sometimes a mother goes full term in her pregnancy and still gives birth to a low birth weight baby. In most cases, these babies are relatively healthy, just small. The parent’s genetics or other factors such as the expectant mother’s lifestyle while she was pregnant may be reasons why a full term baby is born with a low birth weight.  There are two major kinds of intrauterine growth restriction infants, symmetrical and asymmetrical, with symmetrical having a greater frequency of medical issues.

Other factors for low birth weight babies include:

  • Previous pregnancy resulted in a low birth baby or premature birth
  • Multiple fetuses (twins, triplets, etc.)
  • Uterus abnormalities
  • Cervix abnormalities
  • Maternal chronic health problems during pregnancy
  • Maternal high blood pressure
  • Maternal diabetes
  • Smoking
  • Alcohol or drug usage or abuse
  • Infections in the mother
  • Infections in the fetus
  • Inadequate maternal weight gain
  • African-American women
  • All women under 17 are at an increased risk of delivering a low birth weight baby

Preventing a Low Birth Weight Baby

There are many things an expectant mother can do to help reduce the chances of delivering a baby with low birth weight. The most important thing any mother can do is to see her health care provider on a regular basis. Regular check-ups can ensure that both mother and baby are healthy, growing, and developing properly. The health care provider can also help the expectant mother to manage any illnesses, conditions, or mental health issues she may have while she is pregnant.

Folic acid plays a major role when preventing any type of birth defects or health problems. Four hundred micrograms of folic acid daily (usually starting before conception) can reduce the chances of your baby being born with low birth weight and/or other health factors like neural tube defects. If a mother smokes, a good time to quit is when she finds out she’s pregnant. Most health care providers say it’s best to quit smoking three months before conception, but not all pregnancies are planned. For mothers with a previous infant with a neural tube defect, 1 gram of folic acid a day is recommended, and folic acid supplementation should be ongoing, as a mother should be taking folic acid at least 3 months PRIOR to conception.

Low Birth Weight Treatment

If you have a baby born with low birth weight, he or she may need to spend additional time in the hospital for close monitoring. This can last days, weeks, or months depending on how much your baby weighed at birth, the reason for the low birthweight, and how long it takes him or her to reach the appropriate weight to go home. Many hospitals have a specific weight requirement for discharge, but it is not always an absolute number and depends on the underlying causes and issues. In most cases, an ultrasound can inform the doctor before the baby is born that he or she is not gaining enough weight. The doctor may want to monitor the fetal heart rate and/or perform additional ultrasounds to monitor the baby’s progress. Unfortunately, the only treatment while a mother is pregnant is to monitor and wait. Occasionally, a baby may need to be born prematurely in order to save its life or the mother’s life due to other medical factors.

This page was last updated on 06/2017

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