Babies who are smaller than most other babies of the same gestational age may be called growth-restricted, small-for-gestational age or small-for-date. These babies may be born premature (before 37 completed weeks of pregnancy) or born full term but small. Some of these babies are healthy and are small simply because their parents are smaller than average. Others have low birthweight because something slowed or stopped their growth in the uterus.
About 10 percent of babies are growth-restricted. The good news is that there are steps a pregnant woman can take to help avoid factors that may contribute to premature birth and/or fetal growth restriction. Those factors include:
– Placental problems. These can reduce the flow of blood and nutrients to the baby, limiting growth.
– Birth defects. Babies with certain birth defects are more likely to be growth restricted. Also, babies with birth defects are more likely to be born prematurely.
– Previous birth of a growth-restricted baby. This may increase the risk by about 50 percent in another pregnancy.
– Chronic health conditions in the mother. High blood pressure, diabetes, and heart, lung and kidney problems sometimes can reduce birthweight.
– Smoking. Pregnant women who smoke cigarettes are nearly twice as likely to have a low-birthweight baby as women who do not smoke. Smoking slows the baby’s growth and increases the risk of premature delivery.
– Alcohol and illicit drugs. These may limit the baby’s growth, increase the risk of premature delivery and cause birth defects.
Inadequate maternal weight gain. Women who don’t gain enough weight during pregnancy increase their risk of having a low-birthweight baby.
A health care provider may suspect fetal growth restriction if the mother’s uterus is not growing at a normal rate. He can help confirm this with a series of ultrasounds that monitor how quickly the baby is growing. The provider closely monitors the well-being of a growth-restricted fetus using ultrasound and fetal heart rate monitoring. He also may use a form of ultrasound called Doppler to measure blood flow in the umbilical cord and certain fetal blood vessels. If these tests show that the baby is having problems, the provider may recommend early delivery. In severe cases, this can help prevent stillbirth and newborn health problems.
It is possible that growth restriction before birth may result in problems in adulthood. It may cause lasting changes in certain insulin-sensitive organs like the liver, skeletal muscles and pancreas. Before birth, these changes may help the malnourished fetus use all available nutrients. However, after birth these changes may contribute to some health problems.
The March of Dimes has funded research in the area of fetal growth restriction. Grantees are investigating the role of certain genes in fetal growth restriction, as a step toward developing treatment to prevent this problem or improve the growth of affected babies.
The March of Dimes also promotes the health benefits of smoking prevention and cessation by providing educational materials for consumers and supporting projects that increase smoking-cessation services available to pregnant women who smoke. Women who quit smoking, avoid alcohol and drugs, control chronic medical conditions and maintain a healthy weight during their pregnancy are doing a great deal to help prevent fetal growth restriction.