If you have missed your period, then you could take a pregnancy test this week. This would be the earliest that a home pregnancy test can detect pregnancy.

By around the end of week 4, the cluster of cells finishes implanting into the womb lining and is now known as an embryo. A membrane called the amniotic sac is forming around the embryo. It is filled with a clear liquid called amniotic fluid, in which the baby floats and is cushioned. Increasing levels of the pregnancy hormone chorionic gonadotrophin (HCG) mean that you may be starting to experience some of the signs and symptoms of pregnancy.

Babies are still very small at this point, and sizes vary from 0.014 inch to 0.04 inch in length.

You may begin to exhibit some of the early pregnancy symptoms such as breast tenderness, headache, backache, needing to urinate more often, and feeling more tired than usual. At this time your tastes might start changing. You might start craving particular foods, or developing a dislike for certain things such as coffee or alcohol. These are sometimes things that you need to cut back on anyway before and during pregnancy (such as alcohol). Don’t force yourself to eat foods that make you feel ill, but remember you still need to eat a healthy balanced diet.

There are three layers to your baby- the ectoderm, mesoderm, and endoderm. These three layers will form the baby’s organs and tissues. The ectoderm will become the nervous system (which includes the brain), skin, hair, nails, mammary glands, sweat glands, and enamel for the teeth. The mesoderm will become the heart, circulatory system, skeleton, connective tissues, blood system, urogenital system, and the muscles. The endoderm will house the lungs and develops into the lining of the gastrointestinal tract, the liver, pancreas, and thyroid.
Arm and leg buds begin developing, but are not clearly distinguishable. The placenta has also begun to form and is producing some important hormones including hCG. There is movement of rudimentary blood through the main vessels.

You need to begin looking for a health care provider and decide where you will have your baby. Arrange appointments with doctors so that you can meet them and ask them questions before deciding if they will become your provider.