A woman is not able to feel her baby move while in the first trimester according to the Office on Women's Health. Although this is a time of extreme growth for the fetus, the baby is too small for the mother to feel any movement yet.
According to What to Expect, if the mother is very thin or has already had a child, she may notice movement as soon as the fourth month of pregnancy. The first sensation of movement is called fluttering, and most expectant mothers can notice this by the fifth month. If the mother has not felt any movements by the fifth month, an ultrasound may be ordered to check on the fetus.