Fetal undergrowth has been defined as the group of newborns occupying less than 10% frequency of the body weight percentage. But recently, after considering the mother's race, number of deliveries, body weight, and height, about 20-60% of the less than 10% group babies are known to grow normally later. Babies with growth problems have a high chance of contracting such fetal diseases as fetal asphyxia, hypoglycemia, and hypothermia. The following are factors in causing fetal undergrowth in infants.
# Family factor: if the mother's small in stature, and has a small skeletal structure, the infant can be small too, and this can't be seen as abnormal
# Insufficient nutrition of the mother: insufficient weight gain between 14-15 weeks and 30 weeks, and undernourishment are causes
# Mother's smoking, drinking, and drug abuse
# Fetal infection: the fetus was infected by bacteria, virus, or parasites in the uterus
# Congenital deformity
# Fetal bone disease
# Exposure to chemicals: cigarettes, alcohol, painkillers, drugs, etc.
# Blood vessel disease of the mother
# Chronic kidney disease
# Hypoxia: heart disease, alpine area
# Anemia of the mother
# Placenta and umbilical cord deformation