Final answer:
Infants who are small for gestational age (SGA) are defined by their weight, head circumference, and length being below the 10th percentile compared to other infants at the same gestational age. They may face feeding difficulties and other developmental challenges and require close monitoring.
Step-by-step explanation:
Infants who are small for gestational age (SGA) are characterized most accurately by option B) Weight, head circumference, and length all below the 10th percentile. This definition takes into account that SGA is a condition where the infant's measurements are smaller than what is expected for the number of weeks of pregnancy. An infant is considered SGA when their birth weight and possibly other size measurements like head circumference and length are less than what 90% of other infants weigh and measure at the same gestational age. They may be full-term but still small, often due to factors affecting growth in the womb.
Infants with SGA may face challenges including difficulty feeding and are at risk for later developmental delays if their growth does not catch up after birth. Moreover, fetal growth rate and the length of gestation are important to determine birthweight, and those who experience intrauterine growth restriction (IUGR) may be born SGA even if they are carried to term.
A healthy, well-nourished full-term newborn typically has an average length of about 51 cm (20 in.) and an average birth weight of 3.4 kg (7.5 lb). Babies who are SGA, however, will fall below these numbers significantly. It is essential to monitor the growth and development of SGA infants closely to ensure that they gain weight and grow in length according to their individual growth curves.