The idea of delivering a small baby appeals to many women because they think it may mean an easier labour and delivery. The truth is, babies that are smaller than they were meant to be may have trouble with the process of labour. They are more likely to require emergency forceps or cesarean delivery than healthier, fully grown infants.
As well, once born, these babies are more likely to have problems adjusting to life outside the womb. Most IUGR or small-for-dates babies grow into perfectly healthy, normal children and adults. However, severe IUGR may be associated with permanently small body size, as well as lower IQ scores and other life-long problems. In short, small babies can mean big problems! It is important that expectant families know what they can do to prevent and treat IUGR.
Babies do not come in one perfect size. Some babies are naturally smaller than average. Babies born to small women (under five feet tall and weighing less than 110 pounds), or belonging to certain ethnic groups, are often smaller than those born to taller and heavier people. In the case of twins or triplets, each baby tends to be smaller than the average single baby of the same age. There is only so much room in there and only so much food to go around!
If you are told that your baby is small-for-dates or your doctor is concerned about IUGR, don’t panic. Your doctor will need to confirm IUGR with special tests. Once the situation is clear, your doctor will be able to tell you what you can do to help your baby.
Why would a baby grow slowly in the womb? Babies need oxygen and nutrients from the mother. These travel to the baby through the placenta and the baby’s umbilical cord. If the flow of oxygen and nutrients across the placenta slows, the baby may develop IUGR. If the mother has a poor diet, high blood pressure or some other serious disease during pregnancy, the baby’s growth may be affected.
Smoking causes stunted growth in unborn babies. When a mother smokes, there is less oxygen for her baby. Oxygen is critically important to normal growth. Nicotine from cigarettes is broken down to another chemical called cotinine. Cotinine slows blood flow to the placenta. Alcohol or other drugs like marijuana or cocaine can also stunt the growth of the unborn baby.
Intrauterine growth restriction sometimes occurs for reasons beyond either a mother’s or doctor’s control. Sometimes there are problems with how the placenta forms early in pregnancy. A malformed placenta cannot deliver the ideal amount of food to the baby.
If such a problem occurs with twins, one baby may get more than a fair share. One twin will be above average size, while the other is much smaller. Certain genetic conditions cause slower growth. Infections in the mother such as toxoplasmosis, rubella (German measles), or cytomegalovirus (CMV) can also stunt the baby’s growth. It might not be obvious that the mother has one of these infections while she is pregnant.
Certain parts of your prenatal visits help you and your doctor to know that your baby is growing well. Your baby’s age before it is born is counted in weeks, from the first day of your last menstrual period until birth. Forty weeks is the usual gestation or time the unborn baby spends growing inside its mother. For instance, a baby at the gestational age of 20 weeks is halfway to its expected birth date. Most of a baby’s weight gain and noticeable growth happens in the last half of pregnancy. The baby gains half of its total weight in the final two to three months. This is pretty obvious to anyone who has already had a baby. Mom’s tummy looks and feels a lot bigger in those last few months!
Your doctor should discuss your personal and family health history, and talk to you about diet, smoking and alcohol and other drug use. You will also receive advice on things that you can do to increase your chances of a healthy pregnancy and birth.
Blood tests done after your first prenatal visit check your chances of catching infections that could hurt your baby. At each prenatal visit your doctor records your weight gain and checks blood pressure. If you are not gaining as much as expected or develop high blood pressure, your baby may be at risk of stunted growth.
Your doctor will also estimate the size of your growing baby by measuring the length from the top of your pubic bone (symphysis) to the top of your uterus (fundus). This measurement is called the symphyseal-fundal height, or SFH. This number is recorded and plotted on a graph on your prenatal record sheet. If the growth of your baby begins to slow or doesn’t reach the normal expected size for its gestational age, you and your doctor need to know why.
The usual first step is to do a detailed ultrasound scan of the baby. The ultrasound pictures let the radiologist measure the baby’s head, abdomen and leg size. These measurements show how well the baby is growing for its gestational age. Doing this test at least twice a few weeks apart helps the doctor to follow and compare the baby’s growth. It is unlikely that a diagnosis of IUGR will be made from a single ultrasound scan. An important part of the ultrasound test involves estimating the amount of amniotic fluid around the baby. Less fluid often goes along with IUGR, suggesting that the placenta is not working well.
Once fetal growth is suspected to be slower than normal, many doctors will ask mothers to do a daily count of their baby’s movements. If you are asked to do this, your doctor will explain what is normal movement, and when decreased movement may be a cause for concern. You will probably also need more detailed ultrasound tests.
The biophysical profile is an ultrasound test where the radiologist measures the volume of amniotic fluid and looks for different types of fetal movements. When a baby rolls and kicks, waves, and practices breathing (yes, babies ‘breathe’ amniotic fluid while in the womb!) it is reassuring even if the baby is not growing as quickly as expected. If IUGR is suspected you may need to have an ultrasound scan every two to three weeks to follow the baby’s growth and well-being very closely. Sometimes, the flow of blood in the baby’s vessels is measured to check to see if the baby is at greater risk.
The non-stress test is another way to check the general health of your unborn baby. During this test, your baby’s heartbeat is recorded over a period of at least 20 minutes. The heart is watched to see if it speeds up when the baby moves, and slows down when the baby is floating quietly. This is normal. Other features of the baby’s heart rate pattern are also important. This test may be done twice a week to be sure that your baby is still doing fine.
Your doctor may refer you to a specialist, or may work together with an obstetrician or perinatologist (a doctor who cares for a baby during birth) to decide on the best care for you and your baby.
If IUGR is discovered early and a clear cause can be found, your doctor can make recommendations. These may include improved diet, stopping smoking, or treating high blood pressure. These changes will help, but not solve the problem. Your baby’s growth should be watched closely with ultrasound measurements.
If this and other tests show that your baby is not very happy with the situation inside the womb, your doctor may recommend bringing on the baby’s birth early. All of these tests help your doctor decide if the risks of being born early are less than the risks of waiting for your baby to get a little older and more ready for the outside world.