Your Baby at 4 Weeks Pregnant
The great divide. Once implanted in the side of your uterus, the fertilized egg divides into layers of cells and officially becomes an embryo. These cell layers will grow into specialized parts of your little one's body, such as the nervous system, skeleton, muscles, and organs.
Support system under way. The placenta, the disk-like organ that connects your circulation to the embryo's, begins to form and attaches to the uterine wall where the egg is implanted. The umbilical cord comes out of one side of the placenta. The amniotic fluid, which will cushion your little one throughout the pregnancy, is already forming inside an encircling sac.
Measuring up. By the end of the week, the embryo measures around 0.04 inch — about the size of a poppy seed.
Your Pregnancy at 4 Weeks
Signs of life. A missed period may still be the only indication that you're pregnant. You might experience some spotting as your fertilized egg implants into the uterus. This light bleeding is known as implantation spotting and it's completely normal.
The results are in. A home pregnancy test should show a positive result, thanks to the hormone hCG released by the brand-new placenta. This same hormone is largely responsible for the nausea that many women experience in the first trimester. Most home pregnancy tests are accurate after your first missed period, but false negatives do happen.