First Trimester Pregnancy Information
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First Trimester Pregnancy Information

A positive pregnancy test sets you on track for a whirlwind of emotions and physical changes. Knowing what to expect during your first trimester makes the beginning of the pregnancy easier to handle for some women. Pregnancy feels different for every woman and not everyone experiences the same symptoms or physical changes, but many first trimester experiences are similar with all women.

Time Frame

The first trimester spans from week one to week 12 of the pregnancy. The first two weeks are actually before conception occurs. The 40 weeks of a pregnancy are calculated starting on the first day of your last period, but conception doesn’t usually happen until about two weeks later. Fertilization of the egg typically happens in week three, followed by implantation in week four. The baby becomes an embryo in week five. Much of the baby’s development begins at that point.


Many possible symptoms occur during the first trimester. You might experience only one or you might feel them all. Nausea, often called morning sickness, is a common first trimester experience for women. Fatigue is another common symptom in early pregnancy. You might also experience breast soreness or tenderness, bloating, constipation, frequent urination, headaches, food cravings or food aversions. As the end of the first trimester nears, many of the symptoms will decrease or subside in some women.

Baby Development

As an embryo, your baby begins developing his major organs, including the heart, brain and spinal cord. The heart begins pumping blood around week six of the pregnancy. At the same time, your baby begins developing facial features and buds for his arms and legs. At eight weeks, the baby begins moving. Week 11 marks the baby’s status as a fetus. The baby has arms, legs and even external genitalia. The baby grows from about 1/16 inch at week five to 2 1/2 inches by week 12.

Healthy Choices

Because of all the development that occurs in the first trimester, healthy choices on the part of the mother are essential. A prenatal vitamin with at least 400 mcg folic acid helps with proper neural tube development early in the pregnancy. A healthy diet and exercise keeps your body healthy overall, which benefits the growing baby. Avoid smoking, illegal drugs and alcohol throughout the pregnancy. A woman currently taking prescription or over-the-counter drugs should talk to her physician immediately to determine if it is safe to continue the medication.

Prenatal Care

Prenatal visits usually begin during the first trimester. Contact your physician as soon as you know you’re pregnant to schedule an appointment. The first appointment usually happens around weeks eight through 10. The first exam typically involves an exam complete with medical history and possibly blood tests.

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