Birthweight below a given low percentile limit for gestational age (e.g., birthweight less than 10th percentile for gestational age); typically reflects inadequate supply of nutrients and oxygen to the foetus.

is said of a fetus who does not grow as fast as he should, often because not enough nutrients or not enough blood (and oxygen) arrive to him, or because the fetus has to 'work' harder than usual. In twin-to-twin transfusion, it is often seen in the donor twin, who has to pump blood to himself and to the recipient twin. Intrauterine growth retardation can be seen by ultrasound, when the fetus appears smaller than expected for a given gestational age. At birth, this will lead to a baby who is 'small for gestational age.'

The slow growth of a fetus in the uterus, possibly resulting in a low-birthweight baby.

An infant, of any gestational age, whose intrauterine growth was less than expected. There are numerous causes, including infection and placental dysfunction.

development of the fetus that is delayed related to gestational age.

A reduction in fetal growth for reasons such as infection, inadequate placenta, or exposure to teratogens.

An abnormal condition in pregnancy in which the fetus is small for its gestational age. Causes of delayed development and maturation include genetic factors, maternal disease or fetal malnutrition caused by insufficient placental growth.

The failure of a fetus to maintain its expected growth potential at any stage of gestation. Infants with IUGR may be born at full term but are smaller than expected.

a condition in which the baby does not develop at the rate that it should. There are many different potential causes of IUGR, including poor maternal health or dietary/lifestyle habits, birth defects, DES exposure, and progesterone deficiency.