First trimester pregnancy
From our partner site on breast cancer, MyBreastCancerNetwork.com.
The first trimester of pregnancy begins when a fertilized egg implants into a woman's uterus. This occurs about 7 days after the egg is fertilized.
The first trimester ends when the fetus is about 12 weeks old. (This is about 14 weeks from the first day of the last normal menstrual period.)
Early pregnancy; Pregnant - first trimester
Causes, incidence, and risk factors:
Pregnancy is a normal condition and, in most situations, should not be approached as a problem or disease. Any fertile female engaged in a sexual relationship with a fertile male is at risk of becoming pregnant.