Our Pregnancy Calendar will help you find out how your baby grows and changes from a small group of cells to a fully developed baby ready to begin life.
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3 Weeks Pregnant
Several days after the fertilization, an embryo or morula attaches itself to the internal wall of uterus (endometrium). Now you are officially pregnant! The quantity of cells in the embryo increases up to a ball which releases the enzymes that cause your body to go through changes. For example, you stop having menstruation because of it.
During first few weeks of pregnancy, the embryo continuously develops. Big changes take place everyday. Just within 7 days one cell grows into a ball containing hundreds of cells. Although it can be hard to notice any kind of system under a microscope, all cells function organized. Some of them form the embryo and some others work to support to sustain its life. Blastocyst or a bubble full of fluids is hard to be noticed by an untrained eye and is about 0,0079 (0.1-0.2mm) in diameter. The blastocyst burrows itself into the upper uterine wall from the side where the egg comes from. The bubble starts to attach itself on the 4th-7th day and more securely on the 10th day. The embryo receives its nutrients from the mother and sends it back after processing them. Gradually the mucous uterus grows enveloping the fertilized egg forming the placenta, an organ which feeds and protects the embryo throughout the pregnancy. Embryo grows by one tenth of its previous size.