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Pumping & Storing Breastmilk
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Pregnancy Calendar

Week 04: Your pregnancy

Week 4: Your pregnancy

Your baby's growth: spinal cord and brain sections

At the beginning of this week, the fertilized egg is a fluid-filled cluster of rapidly multiplying cells. The egg tunnels into the uterus where it promptly divides into two parts. Half the egg attaches to the uterine wall and develops into the placenta, which will transport oxygen and nutrients to your baby and waste products away from your little one during the next nine months. The other half will develop into the embryo, which will later become the fetus.

During this week the following occurs:

  • Spinal cord development. A sheet of cells on the back of the embryo folds in the middle to form a tube that will become the baby's spinal cord.
  • Brain section development. At the other end, the tube enlarges to form the brain's major sections.

What's happening with you

  • Pregnancy symptoms. The hormones your ovaries are already secreting may trigger your first symptoms of pregnancy this week including fatigue, tingling and aching breasts or nausea.
  • Missed period and possible spotting. By the end of the week you may notice that you've missed your period, although some women do experience spotting—also called implantation bleeding. Typically this bleeding is lighter than your normal period. If you have questions or concerns, it's always best to talk with your physician.

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