The first trimester of pregnancy begins when a fertilized egg implants into a woman's uterus. This occurs about 7 days after the egg is fertilized.

The first trimester ends when the fetus is about 12 weeks old. (This is about 14 weeks from the first day of the last normal menstrual period.)

Pregnancy is a normal condition and, in most situations, should not be approached as a problem or disease. Any fertile female engaged in a sexual relationship with a fertile male is at risk of becoming pregnant.

• Missed menstrual period(s)
• Fatigue
• Breast enlargement or breast discomfort (tenderness)
• Abdominal distention
• Nausea with or without vomiting
• Light-headedness or actual fainting
• Skin areas appearing abnormally dark or light

The health care provider will perform an examination, which may reveal:

• an enlarged uterus -- the top of the uterus (the fundus) may be felt by touch
• a bluish or purple coloration of the vaginal walls and cervix
• softening of the cervix
• weight changes (usually weight gain, although weight loss could occur if nausea and vomiting are significant).
• increased size of the abdomen

Tests include:

• A positive urine and/or serum HCG (pregnancy test)
• A pregnancy ultrasound to confirm or check accurate dates for pregnancy

Pregnancy may also alter the results of numerous laboratory tests.

Prior to modern medicine, many mothers and their babies did not survive pregnancy and the birth process. Today, good prenatal care can significantly improve the quality of the pregnancy and the outcome for the infant and mother.

Good prenatal care includes:

• Good nutrition and health habits before and during pregnancy
• Frequent prenatal examinations to detect early problems
• Routine ultrasounds to detect fetal abnormalities and problems
• Routine screening for:
  • Sexually transmitted diseases
  • Rubella immunity
  • Blood type problems (Rh and ABO)
  • Diabetes
  • Genetic disorders -- if there is a family history or the age of the mother indicates the need
  • Blood pressure abnormalities
  • Urine protein

Women who choose to have an abortion usually do so in the very early stages of the pregnancy (usually before 12 weeks gestation). Abortion is legal through the 24th week of pregnancy. The abortion procedure, however, becomes more difficult with advancing gestational age, and many providers do not perform pregnancy terminations in the second trimester.

Women who plan to continue a pregnancy to term need to choose a health care provider who will provide prenatal care, delivery, and postpartum services. Provider choices in most communities include:

• physicians specializing in obstetrics and gynecology (OB/GYN)
• certified nurse midwives (CNMs)
• some family practice physicians
• some family nurse practitioners (FNPs) or physician assistants (PAs) who work in conjunction with a physician

Family health care providers, or generalists, are proficient in managing women throughout normal pregnancies and deliveries. If a problem in the pregnancy is identified, a generalist will refer the patient to obstetric specialist.

The goals of prenatal care are to:

• monitor both the pregnant woman and the fetus throughout the pregnancy
• identify anything that could change the outlook for the pregnancy from normal to high-risk
• explain nutritional requirements throughout the pregnancy and postpartum period
• explain activity recommendations or restrictions
• address common complaints that may arise during pregnancy (for example, backache, joint pain, nausea, heartburn, headaches, urinary frequency, leg cramps, and constipation) and how to manage them, preferably without medications

Women who are considering becoming pregnant, or who are pregnant, should eat a balanced diet and take a vitamin and mineral supplement that includes at least 0.4 milligrams (400 micrograms) of folic acid. This level of folic acid supplement has been shown to decrease the risk of certain abnormalities (such as spina bifida).

Pregnant women are advised to avoid all medications, unless the medications are necessary and recommended by a prenatal health care provider. Women should discuss all medication use with their providers.

Pregnant women should avoid all alcohol and drug use. They should not smoke. They should avoid herbal preparations and common over-the-counter medications that may interfere with normal development of the fetus.

Prenatal visits are typically scheduled:

• every 4 weeks during the first 32 weeks of gestation
• every 2 weeks from 32 to 36 weeks gestation
• weekly from 36 weeks to delivery

Weight gain, blood pressure, fundal height, and fetal heart tones (as appropriate) are usually measured and recorded at each visit, and routine urine screening tests are performed.

About 10% of known pregnancies terminate spontaneously -- usually during the first trimester. (See miscarriage.) As many as 50 - 70% of all conceptions terminate spontaneously before the woman is even aware of pregnancy. Many of these occur because there is a problem with the developing fetus.

Abnormal or high-risk situations, which may prove dangerous to the health of the mother or fetus, may occur in up to 20% of pregnancies.

Call for an appointment if you suspect you are pregnant, are currently pregnant and are not receiving prenatal care, or if you are unable to manage common complaints without medication.

Call your health care provider if you suspect you are pregnant and are on medications for diabetes, thyroid disease, seizures, or high blood pressure.

Notify your health care provider if you are currently pregnant and have been exposed to a sexually transmitted disease, chemicals, radiation, or unusual pollutants.

Call your health care provider if you are currently pregnant and you develop fever, chills or painful urination.

It is urgent that you call your health care provider if you are currently pregnant and notice any amount of vaginal bleeding, the membranes rupture (water breaks), or you experience physical or severe emotional trauma.

There are a variety of birth control methods designed to prevent pregnancy. These include the condom, female condom, IUD, birth control pill, hormone injections/implants, diaphragm, and family planning.

For example, women who use Depo-Provera injections or progestin implants have less than 1 pregnancy per 100 women per year. Couples who use the rhythm or calendar methods have between 20 to 30 pregnancies per 100 women per year.

The only 100% effective means of contraception is complete abstinence.