By Bill Kray
The baby within is not an "it" or even an infant.
Obstetricians specialize in treating matters of pregnancy and birth. Usually, by means of ultrasound, progressive prenatal development is monitored by means of ultrasound imaging.
Embryo: First stage of baby development from the moment of fertilization.
Fetus: Development from the eighth week of conception.
Infant: Very young speechless child.
An embryo about the size of a sesame seed is the first thing noticed in a pregnancy test. By the fifth week of development, the embryo has a heartbeat in the early ultrasounds. The fetus undergoes significant changes throughout pregnancy. These are beautifully illustrated on the anatomy poster entitled, Prenatal Development, available here.