What is Low Birth Weight?


Low birth weight (LBW) is defined as a birth weight of a liveborn infant of less than 2,500 g (5 pounds 8 ounces) regardless of gestational age. LBW is either caused by preterm birth (that is, a low gestational age at birth, commonly defined as younger than 37 weeks of gestation) or the infant being small for gestational age (that is, a slow prenatal growth rate), or a combination of both.

In general, risk factors in the mother that may contribute to low birth weight include young ages, multiple pregnancies, previous LBW infants, poor nutrition, heart disease or hypertension, drug addiction, alcohol abuse, and insufficient prenatal care. Environmental risk factors include smoking, lead exposure, and other types of air pollutions.

Four different pathways have been identified that can result in preterm birth and have considerable evidence: precocious fetal endocrine activation, uterine overdistension, decidual bleeding, and intrauterine inflammation/infection. From a practical point a number of factors have been identified that are associated with preterm birth, however, an association does not establish causality.

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.