What to Expect During Your First Trimester of Pregnancy
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What to Expect During Your First Trimester of Pregnancy

The first trimester of your pregnancy can be an exciting time, but it can also be one of the most difficult. You may experience hormonal changes and other symptoms, or you may show no signs of pregnancy. With the variation from woman to woman, it may help to have a basic guideline of what to expect in your first trimester.

Time Frame

The first trimester covers the first three months of your pregnancy and includes week 1 to week 14 of the gestation period. The exact date of conception is something most doctors cannot determine, so the typical practice is to count your pregnancy weeks from the first day of your last menstrual period, according to the American Pregnancy Association. Your doctor will use other diagnostic tests, like ultrasound, to confirm the gestation period. Using this system, you may count weeks prior to actually being pregnant, as it can take a week or two for a fertilized egg to attach to your uterus.


If this is your first pregnancy, you should not expect to show until the last week of the first trimester. Some women don’t look pregnant until they are in their second trimester. At week 5, the Mayo Clinic begins reporting the size of your baby with an average length of 1/16 inch to 1/8 inch. By the end of the first trimester, your baby will average 2 ½ inches in length and ½ oz. in weight.


During your first trimester, your baby will develop from a cluster of cells into an embryo. Pregnancy tracks the growth of your baby by each week and shows the important milestones of development. During this time, your baby will grow organs, arms, legs, cartilage, bones and its genitals.

Pregnancy Symptoms

For many women, the first sign of pregnancy is a missed period. As you baby grows, you may experience other pregnancy symptoms. The March of Dimes lists common ones, which include backache, abdominal pain or cramping, heartburn, feeling nauseated, breast changes and fatigue. When the fertilized egg implants in your uterus, you may have some abdominal pain and spotting, a few drops of blood visible in your underwear or on toilet paper.

Expert Insight

The first trimester is a good time to find a medical care provider who will work with you throughout your pregnancy and delivery. The doctor will help you determine what steps you should take for a healthy pregnancy. According to the Palo Alto Medical Foundation, you may need to modify your diet to ensure your baby gets the proper nutrition, begin taking a prenatal vitamin, stop any behavior that could increase pregnancy risks and discuss options like breastfeeding and delivery preference.


Heavy bleeding, which is enough blood to fill a maxi pad, is not a common pregnancy symptom. If this occurs–with or without pain–contact your health care provider as soon as possible. The Mayo Clinic includes these signs as potential indicators of a miscarriage.

Photo Credit

  • pregnant #15 image by Adam Borkowski from Fotolia.com
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