* The term small fetus for gestational age is defined as the small size of the fetus than the usual rate for fetuses of the same gestational age, and this is often due to the presence of problems that cause the determination of the fetus’s growth inside the uterus (in English: Intrauterine Growth Restriction), as a result of lack of delivery  Sufficient quantities of food and oxygen to the fetus during its development, and the pathological causes associated with the small size of the fetus can be explained as follows:

 * Determining the growth inside the womb may result from the mother's injury to some health disorders, and these reasons can be explained as follows:

 High blood pressure or heart disorders.  Kidney or lung disease.  Sickle cell anemia, or other types of anemia.  Infections such as: syphilis, cytomegalovirus, rubella, and toxoplasmosis (in English: syphilis).  Diabetes in its advanced stages.  Antiphospholipid syndrome (English: Antiphospholipid syndrome).

 Factors related to the placenta and uterus leading to small fetus size can be explained as follows:

 Infection of the tissues surrounding the fetus.  Decreased blood supply to the placenta and uterus.  Placenta praevia  Which is the connection of the placenta to the lower part of the uterus.  Detachment of the placenta (English: placental abruption) from the uterus.  Factors related to the fetus Factors related to the fetus that cause its small size can be explained as follows:

 * The occurrence of chromosomal imbalances in the fetus.  Congenital anomalies and disorders.  Pregnancy with more than one fetus.  Infection of the fetus.  Unsatisfactory reasons Not all children of small size at birth suffer from the determination of growth inside the womb, as almost two thirds of them do not suffer from any pathological disorders, they are only smaller in size compared to others, which is common among some families,

 The sex of the fetus: the males are usually larger.  The height and weight of the mother: It was found that the increase in the weight and height of the mother is related to her delivery of larger children.

 Ethnicity: The races that originate in South Asia, for example, are usually smaller.  Number of previous births: As the fetus usually increases weight with each pregnancy of the mother.  The weight of both the father and the mother at their birth.

 * The main risk factors that increase the risk of developing small fetus size can be stated as follows: A pregnant woman is over forty years old.  Smoking or cocaine use.  Get vigorous exercise.  Previous delivery of a baby of small size for gestational age.  An earlier stillbirth.  Maternal malnutrition.  Housing in higher ground.