Low birth weight (LBW) infants are babies that are born weighing less than 2.5 kgs; whereas an average infant weight should ideally be about 8 pounds or more. Infant weight is a key determinant of survival, health and development of the child. It is also a dominant factor contributing towards infant morbidity and mortality, but if treated and cared for properly, low birth weight infants can develop normally with minimum complications. Though, it is important to understand what factors contribute towards low birth weight, so that the problem can be treated effectively.

Causes of Low Birth Weight

One of the prime causes of low birth weight is premature birth of the baby – implying that the baby was born before 37 weeks of pregnancy resulting in less time in mother’s womb for growth and gaining weight since most of the weight is gained by the baby during the last few weeks of pregnancy.

Another, significant cause of low birth weight is a problem called intrauterine growth restriction (IUGR), which implies improper growth of baby even during pregnancy. Infants that are affected by this condition could be born with low birth weight in spite of having completed the entire pregnancy term. However, IUGR can also result in premature birth. The condition may be caused due to fetal, placental or maternal factors or a combination of these.

Maternal Factors Contributing to Low Birth Weight

One of the prime causes of low birth weight in infants are maternal factors affecting the fetus in utero and the impact on fetus. Some maternal factors contributing to low birth weight are:

  • Age: Mothers of age 20 years or below are more likely to have babies that have low birth weights.
  • Interval between pregnancies: The lesser the gap between two consecutive pregnancies, higher are chances of the infant being born with low birth weight
  • Height: The height of a mother affects the birth weight of the infant; if the mother’s height is not more than 145 cms, there are higher chances of the infant being born with low birth weight.
  • Pre-pregnancy body mass index: Higher the body mass index of the mother, lesser are chances of low birth infants being born.
  • Haemoglobin levels: Pregnant women who have haemoglobin levels lower than 11g/dl are more prone to have children with low birth weight.
  • Previous pregnancies resulting in still birth, neonatal death, etc.
  • Multiple and consecutive abortions: Women who have had three consecutive abortions are more likely to have premature children or infants born with low birth weight.
  • Preeclampsia: Preeclampsia affects the arteries that supply blood to the placenta, when these arteries are compromised the placenta does not get enough blood that hampers the supply of blood, nutrients and oxygen to the baby, leading to slow growth and low birth weight or preterm birth.
  • Hyper-anxiety and stress: Excessive anxiety and acute stress during pregnancy can cause preterm birth and low birth weight. Depression has also been linked to low birth weight among infants.
  • Renal insufficiency: Renal insufficiency negatively affects the pregnancy and can cause low birth weight in infants.
  • Cardio-respiratory diseases: Cardio-respiratory issues such as asthma in pregnant women increases the risk of low birth weight in infants.
  • Autoimmune disorders: For women who have autoimmune disorders such as thyroiditis before pregnancy, which is not controlled – have higher chances of giving birth to low birth weight infants.

Factors such as diabetes, malnutrition, bleeding, infection and fetal anomalies – also increase the likelihood of mothers giving birth to low weight infants.

Risk Factors for Low Birth Weight

Several factors other than pre-mature birth and IUGR, can also cause higher risk of low birth weight. These include:

  • Infection during pregnancy
  • Not gaining adequate weight during pregnancy
  • Smoking
  • Alcohol
  • Drug abuse
  • Previous pregnancy with low birth weight delivery
  • Race – African-American

Symptoms of Low Birth Weight

Apart from infants weighing less than 2.5 kg at birth, infants that have low birth weight seem much smaller as compared to those with normal weight. Moreover, the infant has very low body fat and also may have a head that looks bigger in proportion to the entire body.

Diagnosis of Low Birth Weight

Weight of infants is measured right after their birth. A baby weighing less than 2500 grams or 2.5 kgs is considered to be born with low birth weight; a baby weighing less than 1500 grams at birth are considered to have very low birth weight; and a baby weighing less than 1,000 grams at birth has very low chances of survival.

Low birth weight is checked during pregnancy via ultrasound that provides assessment of baby’s growth and development. Low birth weight can also be detected during pregnancy and that is the main reason regular health check-ups during pregnancy are recommended. These tests help determine growth of the baby during pregnancy via methods such as fundal height, which is measured from the top of the pubic bone to top of the uterus. The fundal height (in cms) is of the same as the number of weeks of pregnancy. In case, the fundal height is lower than expected, the growth of the baby is not appropriate.

Treatment of Low Birth Weight

Most babies grow normally if they do not have any other complications other than low birth weight; however, infants that weight even lower than 1 pound are less likely to survive. That said, the treatment of low birth weight depends on the symptoms, age and general health of the infant. Some treatment options include:

  • Neonatal intensive care unit (NICU)
  • Temperature-controlled rooms and bed
  • Feeding the baby through intravenous lines

Complications of Low Birth Weight

Though not all low birth weight infants tend to face similar problems; however some of the complications that arise because of low birth weight in infants are:

  • Oxygen problem at birth
  • Problem in staying warm due to lack of fat
  • Problems in feeding
  • Inability to gain weight
  • Nutritional deficiency
  • Breathing problems
  • Immature lungs
  • Problems with nervous system
  • Digestive issues
  • Sudden infant death syndrome (SIDS)
  • Cerebral palsy
  • Vision problems
  • Deafness
  • Delayed growth and development

That said, maternal factors and other reasons affecting infants and causing low birth weight can be prevented by following a healthy diet during pregnancy, avoiding alcohol, and quitting smoking and drugs. Moreover, regular health check-ups promote proper growth and steady nutritional to the baby, they help monitor any problems and take preventive steps.