Most women equate a missed menstrual period with the possibility of being pregnant, but other symptoms and signs are frequently experienced by many women in the early stages of pregnancy. It's important to remember that not all women will experience these symptoms or have the symptoms to the same degree. Even the same woman can have different types of symptoms in a subsequent pregnancy than she had in previous pregnancies, and symptoms can change or develop on a weekly basis.

Ectopic pregnancy symptoms, or tubal pregnancy symptoms, are very similar to normal pregnancy symptoms at the outset and can include many of the symptoms described below. However, with a tubal or other type of ectopic pregnancy, other symptoms, such as abdominal pain and vaginal bleeding, develop over time, usually 6 to 8 weeks after a missed menstrual period.

The following are the most common pregnancy symptoms in the first trimester.

Missed period

A missed menstrual period is most often the first sign of pregnancy and is a common first trimester symptom. Sometimes a woman who is pregnant may still experience some bleeding or spotting around the time of the expected period, typically 6 to 12 days after conception. When it occurs, this so-called "implantation bleeding" is generally not as heavy or long as a regular menstrual period. This small amount of bleeding that happens at the time of the expected menstrual period occurs because the fertilized egg attaches to the uterine wall. This is referred to as implantation bleeding.

Any bleeding during pregnancy is typically lighter than that observed during the regular menstrual period. However, if a woman does not have regular menstrual cycles, she may notice some of the other symptoms of early pregnancy before it is apparent that the menstrual period has been missed. A missed menstrual period also does not confirm that a woman is pregnant even if she has regular cycles, since both emotional and physical conditions may cause absent or delayed periods.

Breast swelling, tenderness, and pain

Feelings of breast swelling, tenderness, or pain are also commonly associated with early pregnancy. These symptoms are sometimes similar to the sensations in the breasts in the days before an expected menstrual period. Women may also notice a feeling of heaviness or fullness in the breasts. These symptoms can begin in some women as early as one to two weeks after conception.

Abdominal cramping and bloating

Some women may experience feelings of abdominal enlargement or bloating, but there is usually only a small amount of weight gain in the first trimester of pregnancy. In this early stage of pregnancy a weight gain of about one pound per month is typical. Sometimes women also experience mild abdominal cramping during the early weeks of pregnancy, which may be similar to the cramping that occurs prior to or during the menstrual period.

Food cravings

Many women report cravings for certain foods during the early stages of pregnancy. These cravings can persist throughout the entire pregnancy.

Fatigue and tiredness

Fatigue and tiredness are symptoms experienced by many women in the early stages of pregnancy, and some women report feeling fatigued even in the weeks immediately prior to conception. The cause of this fatigue has not been fully determined, but it is believed to be related to rising levels of the hormone progesterone. Of course, fatigue is a very nonspecific symptom that can be related to many causes other than pregnancy.

Elevated basal body temperature

A persistently elevated basal body temperature (the oral temperature measured first thing in the morning, upon arising from sleep) is another characteristic sign of early pregnancy. An elevation in the basal body temperature occurs shortly after ovulation and persists until the next menstrual period occurs. Persistence of the elevated basal body temperature beyond the time of the expected menstrual period is another sign of early pregnancy.

Nausea and vomiting

Nausea and vomiting are also common in early pregnancy. Traditionally referred to as "morning sickness," the nausea and vomiting associated with early pregnancy can occur at any time of the day or night. Its typical onset is anywhere between the 2nd and 8th weeks of pregnancy. Most women who have morning sickness develop nausea and vomiting about one month after conception, but it may develop sooner in some women. Sometimes women report an increased in sensitivity to certain odors or smells that can sometimes cause nausea and/or vomiting.

Elevations in estrogen that occur early in pregnancy are thought to slow the emptying of the stomach and may be related to the development of nausea. Accompanying the characteristic "morning sickness" may be cravings for, or aversions to, specific foods or even smells. It is not unusual for a pregnant woman to change her dietary preferences, often having no desire to eat previous "favorite" foods. In most women, nausea and vomiting begin to subside by the second trimester of pregnancy.

Frequent urination

A woman in the early stages of pregnancy may feel she has to urinate frequently, especially at nighttime, and she may leak urine with a cough, sneeze, or laugh. The increased desire to urinate may have both physical and hormonal causes. Once the embryo has implanted in the uterus, it begins to produce the hormone known as human chorionic gonadotrophin (hCG), which is believed to stimulate frequent urination. Another cause of frequent urination that develops later is the pressure exerted by the growing uterus on the bladder, but this does not cause frequent urination until the second and third trimesters when the fetus is substantially larger.

Changes in nipple color

Women may notice a deepening of the color of the area surrounding the nipple and/or a dark line going down from the middle of the central abdomen area to the pubic area (known as the linea nigra). Some degree of darkening of the areola persists after pregnancy in many women, but the linea nigra typically disappears in the months following delivery of the baby.

Melasma (darkening of the skin)

Some women may develop a so-called "mask of pregnancy" in the first trimester, referring to a darkening of the skin on the forehead, bridge of the nose, upper lip, or cheeks. The darkened skin is typically present on both sides of the face. Doctors refer to this condition as melasma or chloasma, and it is more common in dark-skinned women than those with light skin. Melasma can also occur in some conditions other than pregnancy. Women who have a family history of melasma are at greater risk of developing this sign of pregnancy.

Mood swings and stress

Mood swings and stress are common symptoms reported by many women in the early stages of pregnancy. Many women in the early stages of pregnancy describe feelings of heightened emotions or even long crying. The rapid changes in hormone levels are believed to cause these changes in mood. Pregnant women may also notice more rapid and drastic changes in their moods. As with other nonspecific symptoms, mood swings can be caused by a number of conditions other than pregnancy.

Headaches

Some women report suffering from headaches early on in their pregnancy, which may be related to corresponding changes in hormone levels. These headaches are nonspecific, usually not involving just one side of the head, and are not accompanied by changes in vision.