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4 Weeks Pregnant: Your Baby’s Development

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 different parts of your little one's body, such as the nervous system, skeleton, muscles, and organs.

Support system under construction. The placenta, a disk-like organ that connects your body's systems to your baby'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 membrane sac.

embryo Week 4

4 Weeks Pregnant: Your Symptoms

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 that's 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 can occur. If you have missed your period but show a negative home pregnancy test, you may want to consult your doctor.

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