Pregnancy Home > Pregnancy Week by Week
When you are three weeks pregnant, an egg has been fertilized by a sperm and has been implanted in your uterus. You are now officially pregnant!
During this third week of pregnancy, the fertilized egg divides into hundreds of cells and is now called a blastocyst. When it reaches your uterus, the blastocyst implants itself into the uterine wall (also called the endometrium). The endometrium will provide the developing embryo with nutrients and it will remove waste. Over time, this implantation site will develop into the placenta, which will nourish and protect your developing baby throughout the pregnancy.
By the time you are three weeks pregnant, you should be taking the following supplements to ensure the health and nourishment of your baby:
(Click 3 Weeks Pregnant for more information.)
Four weeks into your pregnancy, implantation has occurred. Once the fertilized egg has reached the uterus, it divides in half. One half sticks to the uterine wall and becomes the placenta, which is the life support system that brings nourishment to your baby and takes waste out. The other half will become the baby. By the time you are four weeks pregnant, you will have missed your period.
At this point in your pregnancy, you will likely experience symptoms such as:
- Sore breasts
- Expanding waistline
- Increased need to urinate
- Mood swings
Some women also notice a metallic taste in their mouth during this time.
The fourth week of pregnancy marks the beginning of the embryonic period, which is when the blastocyst begins to transform into an embryo. The embryonic period is when the baby's brain, spinal cord, heart, and other organs begin to form.
Your baby is now about 0.04 inches long.
(Click 4 Weeks Pregnant for more information.)