Pregnancy is broken into three time periods, called trimesters. Most women feel differently, both physically and mentally, during each trimester. In addition to weight and body shape, other alterations in your body chemistry and function also take place during pregnancy. Your heart works harder, your temperature registers slightly higher, body secretions increase, joints and ligaments are more flexible and hormones are altered.

Mood changes also are common, resulting from a combination of hormonal changes and greater fatigue, as well as normal anxiety over body image, sexuality, finances, partner roles and impending parenthood.

For the vast majority of women, pregnancy follows a fairly routine course. Some women, however, have complications or challenges related to their health or the health of their baby. These women experience what is called a high-risk pregnancy.

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Signs to Watch For

Although there are many symptoms that are a normal part of pregnancy, there are certain danger signs that may indicate problems. You should notify your doctor immediately if you experience any of the following:

  • Persistent vomiting
  • Chills or fever
  • Continuous pain
  • Burning with urination
  • Blurred vision
  • Continuous headache
  • Sudden swelling of the hands or face
  • Five or more uterine contractions per hour
  • Decreased fetal movements
  • Leaking of fluid from the vagina (blood or water). If you have vaginal bleeding at any time during your pregnancy, have someone call your doctor immediately.
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Pregnancy has three trimesters, each of which is marked by specific fetal developments. A pregnancy is considered full-term at 40 weeks; infants delivered before the end of week 37 are considered premature. Premature infants may have problems with their growth and development, as well as difficulties in breathing and digesting.

First Trimester (0 to 13 Weeks)

The first trimester is the most crucial to your baby's development. During this period, your baby's body structure and organ systems develop. Most miscarriages and birth defects occur during this period.

Your body also undergoes major changes during the first trimester. These changes often cause a variety of symptoms, including nausea, fatigue, breast tenderness and frequent urination. Although these are common pregnancy symptoms, every woman has a different experience. For example, while some may experience an increased energy level during this period, others may feel very tired and emotional.

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Prenatal Care

Expert prenatal care ensures that both you and your baby are as healthy as possible throughout your pregnancy. If you think you are pregnant, contact your doctor to make an appointment and establish your prenatal care schedule. During prenatal visits, tests are performed on you and your baby to assess any potential risks, treat any complications, and to monitor the growth and development of your baby.

Many factors affect the number of prenatal visits you have, including your personal health and your doctor's preference. Additional prenatal care may be necessary if you have preexisting medical conditions, such as diabetes, or if complications arise during your pregnancy. If your pregnancy is going well, visits are planned around key pregnancy developments and certain tests that need to be performed.

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Labor is a series of progressive and continuous contractions of the uterus that help the cervix to open and thin, allowing the baby to travel through the birth canal. Labor usually starts within two weeks before or after your estimated delivery date. However, this can vary widely.

Labor and delivery are hard work and involve some discomfort. The level of discomfort experienced during childbirth varies from woman to woman and from pregnancy to pregnancy. Each woman chooses a different way to experience her birth — some prefer to go through it without medication, while others choose to have medication or anesthesia. Many decide to "see how it goes" and make choices as their labor unfolds.

We offer a spectrum of options for managing your pain during labor and delivery. You will be assigned to your own nurse during your stay in the birthing suite. He or she will help keep you comfortable and guide you through non-drug approaches to pain management, such as whirlpool soaks and position changes.

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Reviewed by health care specialists at UCSF Medical Center.