A human’s pregnancy will typically last 40 weeks or about nine months and it is divided into three states, called trimesters. At just four weeks, the unborn baby is developing the brain and spinal cord, it is called an embryo and is only about 1/25 of an inch! At eight weeks, the embryo is called a fetus, and all its major organs are starting to form.
The fetus has its own heartbeat and will be about an inch long. At the end of the first trimester, the fetus now can make a fist! You will also be able to tell the sex since the external organs are visible. The fetus is now about three inches long and weighs about an ounce! During the beginning of the second trimester (12 weeks), the fetus musculoskeletal system continues to grow.
The fetus is a lot more active at 20 weeks and is covered with hair called lanugo. At this point, halfway through the 40 weeks, the fetus is only about 6 inches long and weighs nine ounces. We could go on and on about the development of the fetus until it is born – but wouldn’t it be cool to see the entire process in just about four minutes!