Fertilization happens when an egg and a sperm unite. This is just the first step in combination of intricate events that result in pregnancy. Fertilization occurs in the fallopian tube. Throughout the next several days, the merged egg and sperm proceed through the fallopian tube towards the lining of the uterus. This is where it implants and begins to grow.

The cluster of cells that will reach the uterus becomes the fetus as well as the placenta. The placenta operates like a life-support system in the course of pregnancy. It provides nutrients, hormones, and oxygen from the mother to the fetus. A typical pregnancy will last around 280 days (which is around 40 weeks), starting from the first day of your last menstrual period. Having said that, an ordinary range can be as few as 259 days to approximately 294 days ( roughly 37-42 weeks). The forty weeks of pregnancy are split up into three trimesters. Each trimester will last around 12-13 weeks each (or just about three months). In the course of the pregnancy, the uterus lining will thicken and the blood vessels expand to nourish the fetus. As pregnancy continues, the uterus will expand to provide space for the growing baby. The uterus will be several times its regular size by the time the baby is born.