Intrauterine Growth Retardation (IUGR) or Restriction can have numerous causes, but the most common cause for IUGR is placental insufficiency. In this scenario, the placenta is not delivering the nutrients and oxygen to the fetus like it is supposed to. As a consequence, the infant will grow at a smaller than anticipated rate. This will lead to a small baby with low birth weight. The infant’s weight will be below the 10th percentile on the growth curve. Another way to look at this is 90% of the infants weigh more than the baby with IUGR.
Causes of placental insufficiency which can, in turn, produce IUGR include hypertension (especially uncontrolled), diabetes, autoimmune conditions like lupus, poor nutrition, anemia, certain prescription medications, smoking, placental abruption, and illicit drug usage among others. Sometimes the cause of the placental insufficiency is unknown.
If your provider feels that your uterus is not growing at the anticipated rate, he will order an ultrasound to obtain fetal measurements. Sometimes, the abdomen may look small and measure small, but the ultrasound will show that the fetus is growing at the appropriate rate. Doppler studies, which look at the rate of flow in the umbilical cord, will most likely be performed at the same time as the ultrasound. The placenta will also be assessed to determine the degree of calcification. There are two types of IUGR. One is symmetric IUGR where the fetal head and body are both small, and there is asymmetric IUGR where the head is growing at an appropriate rate, but the body is not. It is important to realize that even though the term “retardation” is used, this does not refer to mental retardation.
If the fetus is found to have IUGR, your provider will start tests to assess fetal well being. One of these is a nonstress test (NST) where a belt is placed around the maternal abdomen, and the fetal heart rate is followed on a monitor. Your provider will be able to tell how the fetus is doing by looking at the fetal heart rate pattern. He will also start biophysical profile testing (BPP) where an ultrasound is used to monitor the infant’s breathing, flexion or extension of the extremities, amount of amniotic fluid, and fetal movement. You will be asked to perform fetal kick counts to make sure that the fetal activity is not decreasing. You will then report any decreased fetal movement to the provider as this can mean fetal compromise. An amniocentesis may also be offered to check for chromosomal abnormalities.
Your provider will elect to continue the pregnancy as long as the fetal tests of well being show that the fetus is not under stress. IUGR infants are at higher risk of being stillborn so the pregnancy will be carefully monitored.
IUGR infants have more difficulty maintaining their body temperature at birth. In addition, they have trouble maintaining their blood glucose and are more prone to infection. Meconium aspiration is common as well.
Your provider may elect to deliver the infant early depending on the severity of the IUGR. He will also recommend early delivery if there is concern about fetal compromise. Delivery will usually be recommended around 37 weeks gestation. The delivery can be vaginal or may be by cesarean if the fetus cannot tolerate the stress of labor. But again, delivery could be earlier than 37 weeks depending how the fetus is doing.
Wishing you a happy and problem free delivery, Pablo.