According to chapter 15; page 484 of Understanding Nutrition; low-risk, and high-risk pregnancy is defined as followed
Low-risk pregnancy - A pregnancy characterized by factors that make it likely the birth will be normal and the infant healthy
High-risk pregnancy - A pregnancy characterized by risk factors that make it likely the birth will be surrounded by problems such as premature delivery, difficult birth, restricted growth, birth defects, and early infanct death
According to chapter 15; page 485 of Understanding Nutrition 13e; Low-birthweight infants are more likely to experience complications during delivery than normal-weight babies. They also have a statistically greater chance of having physical and mental birth defects, becoming ill, and dying early in life. Of infants who die before their first birthdays, about two-thirds were low-birthweight newborns. Very-low-birthweight infants (31/2 pounds or less) struggle not only for their immediate physical health and survival, but for their future cognitive development and abilities as well
According to chapter 15; page 484 of Understanding Nutrition 13e; A high-risk pregnancy is likely to produce an infant with low birthweight. Low-birthweight infants, defined as infants who weigh 5 1/2 pounds or less, are classified according to their gestational age. Preterm infants are born before they are fully developed; they are often underweight and have trouble breathing because their lungs are immature. Preterm infants may be small, but if their size and weight are appropriate for their gestational age, they can catch up in growth given adequate nutrition support. In contrast, small- for-gestational- age infants have suffered growth failure in the uterus and do not catch up as well. For the most part, survival improves with increased gestational age and birthweight.