Pregnancy Trimesters


Your pregnancy is a time of rapid changes for both you and your developing baby. Health professionals commonly refer to the stages of pregnancy as trimesters. Normal pregnancies last approximately 40 weeks from the time of menstruation to delivery. Each trimester includes certain developmental milestones for your baby.

Preconception Planning

Planning for a healthy pregnancy can help strengthen your body and improve your chances of a healthy pregnancy. If you are thinking of getting pregnant, begin by making an appointment with your doctor. Your doctor can test for the presence of health conditions that may affect your ability to conceive, as well as treat conditions that may threaten your future pregnancy. Take advantage of the months before conception to get your body in the best possible shape by eating well and exercising.

First Trimester

The first trimester of your pregnancy begins with your menstrual period and lasts for 13 weeks. During this time, conception occurs and your baby begins to grow. Your baby’s initial development includes the formation of his spine, brain and other organs. Your baby’s heart begins to beat during the first trimester, and his toes and fingers begin to take shape. By the 13th week of your pregnancy, your baby measures about 3 inches long and weighs about 1 oz. Your changing hormones can cause nausea, fatigue and breast tenderness.

Second Trimester

The second trimester of pregnancy lasts from weeks 14 through 24. During this period, your baby may grow to a weight slightly over 2 lb. and a length near 14 inches. Fetal development during the second trimester includes the formation of eyebrows, eyelashes and fingernails. Near the end of your second trimester, your baby develops sleeping and waking cycles. You will probably begin to feel your baby’s movements during the second trimester. Many women experience an increase in breast size as well as skin changes during this phase.

Third Trimester

The third and final trimester begins at 25 weeks and ends when you give birth, normally about 40 weeks after the first day of your last period. During this time, your baby puts on weight, growing longer and heavier. Average newborns weigh around 8 lb. and measure approximately 20 inches long. As labor nears, you may experience backaches, anxiety and swelling around your ankles.


While many pregnancies progress without problems, certain symptoms may signal the need for immediate medical care. Signs to watch for throughout your entire pregnancy include vaginal bleeding, pain during urination, severe cramping, blurred vision, high fever and sudden swelling in your face, feet or hands. Contact your doctor for any problem that seems unusual or worries you.



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