Final answer:
Babies under 1,000 grams (2 pounds 3 ounces) are considered extremely low birthweight, and the health impact of low birthweight includes greater disease susceptibility and increased infant mortality rates. Proper fetal growth and gestation lengths are important for normal birth weight. After birth, healthy infants display rapid growth and weight increases.
Step-by-step explanation:
Babies born under 1,000 grams (2 pounds 3 ounces) are considered extremely low birthweight. Low birth weight is a term designated for babies weighing less than 2.5 kg (5.5 pounds) at birth, which can be due to maternal undernutrition, intrauterine growth restriction, or pre-term birth. These conditions may lead to increased susceptibility to disease and higher mortality rates in infancy.
Undernutrition and growth deficits during pregnancy are significant factors affecting birth weight. The growth rate of the fetus and the length of gestation are two critical determinants of a newborn's weight. Babies categorized as small for gestational age may be born at full term but still, weigh less than the norm due to inadequate growth in utero. Conversely, a rapid increase in weight post-birth could pose a risk for obesity later in life.
Neonatal health and development are closely monitored through growth measurements against standard values. A healthy full-term newborn is expected to have an average birthweight of about 3.4 kg (7.5 pounds), with normal physical development facilitated by newborn reflexes. Infants experience rapid growth after birth, typically doubling their weight by six months and tripling it by one year.