The fetus is thought to have an inherent growth potential that, under normal circumstances, yields a healthy newborn of appropriate size.The maternal-placental-fetal units act in harmony to provide the needs of the fetus while supporting the physiologic changes of the mother.Certain pregnancies are at high risk for growth restriction, although a substantial percentage of cases occur in the general obstetric population.
Fetal growth restriction is the second leading cause of perinatal morbidity and mortality, followed only by prematurity.12 The incidence of intrauterine growth restriction (IUGR) is estimated to be approximately 5 percent in the general obstetric population.3 However, the incidence varies depending on the population under examination (including its geographic location) and the standard growth curves used as reference.4 In assessing perinatal outcome by weight, infants who weigh less than 2,500 g (5 lb, 8 oz) at term have a perinatal mortality rate that is five to 30 times greater than that of infants whose birth weights are at the 50th percentile.5 The mortality rate is 70 to 100 times higher in infants who weigh less than 1,500 g (3 lb, 5 oz).5 Perinatal asphyxia involving multiple organ systems is one of the most significant problems in growth-restricted infants.3Timely diagnosis and management of IUGR is one of the major achievements in contemporary obstetrics.
If the growth-restricted fetus is identified and appropriate management instituted, perinatal mortality can be reduced,6IUGR is the pathologic counterpart of small-for-gestational-age.
An ultrasound examination shows a normal biparietal diameter and head circumference, although the abdominal circumference is 24.5 cm, which is at the 2.5th percentile.
Estimated fetal weight is 1,465 g (3 lb, 4 oz), which places the infant in the 3rd percentile.
Asymmetric growth restriction implies a fetus who is undernourished and is directing most of its energy to maintaining growth of vital organs, such as the brain and heart, at the expense of the liver, muscle and fat.
This type of growth restriction is usually the result of placental insufficiency.
General management measures include treatment of maternal disease, good nutrition and institution of bed rest.
Preterm delivery is indicated if the fetus shows evidence of abnormal function on biophysical profile testing.
Constitutionally small babies are well proportioned and developmentally normal.
Growth-restricted babies, however, are often malnourished or dysmorphic.
Arrested head growth is of great concern to the developmental potential of the fetus.1A 22-year-old woman (gravida 1) presents to the physician who has been providing her prenatal care. At the 32-week visit, her blood pressure was 140/95 mm Hg and she had gained 2.25 kg (5 lb) since her last visit. Fundal height was 28 cm, unchanged from the measurement obtained at the 30-week visit.