Small for Gestational Age

What is small for gestational age (SGA)?

Small for gestational age is a term used to describe a baby who is smaller than the usual amount for the number of weeks of pregnancy. This means that they are smaller than many other babies of the same gestational age. SGA babies may be proportionately small (equally small all over) or they may be of normal length and size but have lower weight and body mass. 

What causes SGA?

Although some babies are small because of genetics (their parents are small), most SGA babies are small because of fetal growth problems that occur during pregnancy. When the fetus does not receive the necessary nutrients and oxygen needed for proper growth and development of organs and tissues. IUGR can begin at any time in pregnancy.

Early-onset IUGR is often due to chromosomal abnormalities, maternal disease, or severe problems with the placenta. 

Late-onset growth restriction (after 32 weeks) is usually related to other problems like high blood pressure.Some factors that may contribute to SGA and/or IUGR include the following:

Maternal factors:

  • High blood pressure
  • Chronic kidney disease
  • Advanced diabetes
  • Heart or respiratory disease
  • Malnutrition, anemia
  • Infection
  • Cigarette smoking

Factors related to the developing baby (fetus):

  • Multiple gestation (for example, twins or triplets)
  • Infection
  • Birth defects

Why is SGA a concern?

When the fetus does not receive enough oxygen or nutrients during pregnancy, overall body and organ growth is limited, and tissue and organ cells may not grow as large or as numerousBabies with SGA and/or IUGR may have problems at birth including the following:•Decreased oxygen levels•Meconium aspiration (inhalation of the first stools passed in utero) which can lead to difficulty breathing•Hypoglycemia (low blood sugar)•Difficulty maintaining normal body temperature.

How is SGA diagnosed?

The baby with SGA is often identified before birth. During pregnancy, a baby's size can be estimated in different ways

1. The height of the fundus (the top of a mother's uterus) can be measured from the pubic bone. If the measurement is low for the number of weeks, the baby may be smaller than expected.

2. Ultrasound. Measurements can be taken of the fetus' head and abdomen and compared with a growth chart to estimate fetal weight

3. Doppler flow. Another way to interpret and diagnose IUGR during pregnancy is Doppler flow, which uses sound waves to measure blood flow. Blood flow through blood vessels in both the fetal brain and the umbilical cord can be checked with Doppler flow studies.

4. Mother's weight gain. A mother's weight gain can also indicate a baby's size. Small maternal weight gains in pregnancy may correspond with a small baby.

Treatment of babies who are SGA

Specific treatment for SGA will be determined by your baby's doctor based on:

  • Your baby's gestational age, overall health, and medical history
  • Extent of the condition
  • Your baby's tolerance for specific medications, procedures.
Babies who are SGA and are also premature may have additional needs including oxygen and mechanical help to breathe, an.especiidentify problems with fetal growth. Eating a healthy diet in pregnancy may also help.