When a baby stops growing inside the womb before birth, we refer to this situation as intrauterine growth restriction or IUGR. However, not all small fetuses have IUGR—they are just smaller than normal.
In this situation, the baby is smaller than normal during pregnancy. In other words, he or she is not growing at the normal rate and subsequently will have low birth at birth.
The causes behind IUGR are varied, but most commonly it is due to a problem in the placenta. Also, genetic disorders, birth defects, infections in the mother, high blood pressure, smoking or drinking too much, drug abuse, certain prescribed medicines, etc. can lead to IUGR.