Pregnancy Stages

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By Michelle McGarry
eHow Contributing Writer

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Pregnancy lasts about 40 weeks, counting from the first day of the woman's last period. It has three stages, known as trimesters, which are benchmarks in the baby's development.

First Trimester

The first trimester is week one through week 12, according to MedicineNet. First trimester symptoms of pregnancy include a missed period, nausea (morning sickness), breast tenderness, fatigue and a frequent need to urinate.

During the first trimester, the woman's egg is fertilized and implants in the uterine wall. This triggers hormonal changes in the woman's body.

Second Trimester

The second trimester is week 13 to week 28. Nausea and fatigue typically diminish, and the mother's abdomen grows. During this stage, mothers usually feel the baby's movement for the first time, often called quickening.

Third Trimester

The third trimester is week 29 to week 40. The baby's development completes during this stage. The first milk, or colostrum, appears in the mother's breasts. Mothers sometimes experience Braxton-Hicks contractions, the uterus's way of preparing for labor.

Labor

By the end of 37 weeks, the baby is considered full term. Labor begins when the cervix has effaced (thinned), contractions begin, and the baby moves down the birth canal.