You are about to embark on a magical journey during which your body changes dramatically in order to nurture and develop the growing life within you. A microscopic egg and its fertilizing sperm develop in a predictable way to produce what will be your new baby in just nine short months. Let s review the highlights of fetal growth and development.
Pregnancy is divided into thirds, or trimesters, each lasting about twelve to thirteen weeks.
Pregnancy lasts, on average, forty weeks or 280 days. For the first eight weeks after fertilization, or ten weeks after the first day of your last menstrual period, your developing baby is called an embryo. During this period, all the major organs are formed but are incompletely developed. After the embryonic period, your baby is called a fetus. While the division into trimesters is somewhat arbitrary, it has some important implications.