Pregnancy Facts

Lighthouse Pregnancy Resource Center

Early Stages

• The gestational age of the fetus is typically determined based on the first day of your last menstrual period (LMP). Fertilization age refers to how long it’s been since conception occurred. Fertilization takes place approximately 14 days after the onset of the last normal menstrual period.

Conception occurs when, during an act of sexual intercourse, a single sperm unites with the egg to form a unique and brand new human life. This tiny new cell is called a zygote. At the moment of conception, the chromosomes and genes from both parents combine to determine all the physical characteristics of the new life: sex, facial features, blood type, hair color, eyes and skin.

• The fertilized egg stays in the fallopian tube for about 3 to 4 days, and is now called an embryo. His or her cells divide continuously while traveling down the fallopian tube before arriving at the uterus. The embryo begins to implant in the lining of the uterus around day 6. Once implantation occurs, hormones alert the mother’s body to nurture the pregnancy and prevent her monthly periods. Some women notice spotting (slight bleeding) around the time that implantation occurs.

Pregnancy is divided into three trimesters:

Pregnancy Milestones:

Check out: to see a baby grow from conception through birth.


- The Developing Human, Clinically Oriented Embryology by Dr. Keith L. Moore and others

- The First 9 Months booklet by Vicki L. Dihle, PA-C and Bradley G. Beck, M.D