Baby. Pregnancy and Childbirth. Baby, Pregnancy, Baby Names, and Parenting. Pregnancy/Birth. Homepage - Pregnancy, Baby, Toddler, Kids. Contest. First trimester of pregnancy: MedlinePlus Medical Encyclopedia Image. The first trimester of pregnancy is the first three months after conception.
Signs of early pregnancy are missed menstrual periods, fatigue, breast enlargement, abdominal distention, and nausea. During this period of time all organ development takes place so the fetus is most susceptible to damage from toxins, drugs, and infections. Updated by: David C.