Find out more . Calendar Find your ovulation or due date here. Make calendar . Trimesters Ask a question about this topic First Trimester Trimesters divide pregnancy into three periods, each about 13 weeks long. For example, your baby's body structure is largely formed and his or her organ systems develop during the first trimester.
Most miscarriages occur during the first trimester.
This could be a sign of spontaneous abortion ectopic pregnancy . During the first three months you will probably gain approximately 2-4lbs. Of this, only 1.7oz will be your baby. During the second 3 months, you will gain about 12lbs. Of this, only 2lbs will actually be your baby.