Although every pregnancy is different, many pregnancies present with similar symptoms during the first week. As the embryo makes its descent through the fallopian tube and implants in the uterus, hormone levels soar and changes abound in the mother's body. While these symptoms can also occur for other reasons, in combination they often suggest that a baby is on the way.
Vaginal bleeding at the time the embryo implants in the uterus can be one of the earliest symptoms of pregnancy, according to the American Pregnancy Association. Implantation occurs six to 12 days after conception. Despite its tiny size, the embryo can disrupt the lining of the uterus enough to cause slight bleeding. Cramping may accompany the bleeding.
In most cases, a woman will miss her menstrual period after the embryo implants. A missed period typically occurs about two weeks after conception, but because women's menstrual cycles vary, this may occur the first week after conception. The hormonal changes set off by implantation typically end menstrual bleeding for the remainder of the pregnancy. Some women do experience bleeding during the first month or two of pregnancy at the times when they would have gotten their periods, but the bleeding is usually lighter and of shorter duration than normal. A missed period can have other explanations, however, including excessive weight gain or loss, hormonal problems and stress.
Many changes occur in the breasts as the pregnancy hormones kick into high gear and the breasts prepare to create milk. Swelling and tenderness of the breasts may begin as early as one to two weeks after conception, as noted by the American Pregnancy Association. Wearing a supportive and well-fitting bra can help alleviate some of this discomfort.
Tiredness or fatigue often sets in during the first trimester, as early as one week after implantation. Increasing levels of the hormone progesterone and lower blood sugar and blood pressure cause the early-pregnancy fatigue, according to the Mayo Clinic. Building a baby from scratch takes a lot out of a body! Many women find that drinking a small amount of caffeine, chewing mint-flavored gum and going for a brisk walk are effective ways to combat fatigue, at least temporarily.