Pregnancy is the nine-month process in which a baby develops inside a woman's womb or uterus. Pregnancy results from intercourse or from in vitro fertilization when a sperm from the male penetrates the woman's ovum or egg when it has been released from one of her ovaries.

This process is called fertilization and the resulting cell is called a zygote. The zygote undergoes cell division and keeps dividing as it passes through the Fallopian tube and is implanted in the uterus. This occurs in about one week's time and the implanted ball of eight cells is then called a blastocyst.

With the blastocyst implanted in the endometrium of the uterine wall, the woman may be said to have conceived and to be pregnant. The endometrium provides the fertilized egg with a natural nesting place and immediate nutrition.

Also at this time, the placenta—a very important exchange and filtering system— begins to develop between mother and baby. Oxygen and nourishment from the mother's blood are filtered through the placenta to the baby, and waste products from the child are returned to the mother through the placenta. The baby and the placenta are connected by the umbilical cord.

A few days after conception, a transparent sheath called the amniotic sac begins to grow around the baby. The amniotic sac fills with special fluid, which acts as a cushion to keep the developing baby safe from outside bounces and shocks. Each day the fluid in the sac is exchanged for new fluid in a continual replacement system.

Typically, just before the birth of the baby the sac breaks, releasing about a quart of water through the vagina. When the amniotic sac releases the fluid, it is said the woman's "water broke" and the birth of the baby, its passage from inside the mother out into the world, is imminent. In a normal pregnancy this usually occurs in the ninth month.

Pregnancy is divided into three-month periods, called trimesters. The first trimester is the first, second, and third months of pregnancy; the second trimester is the fourth, fifth and sixth months; and the third and last trimester is the seventh, eight, and ninth months.

The First Trimester
Despite the woman's unchanged external appearance during the first trimester of pregnancy, many important developments are taking place within her body. By the end of the first month, the developing embryo is about one-tenth of an inch long, has a beating heart, has the beginnings of a head, spinal cord, nervous system, lungs and the buds of arms and legs.

During this phase of critical development the embryo is particularly sensitive to influences which could cross the placenta, such as drugs (including alcohol) or certain infections.

During the second and third months of the first trimester the embryo continues to develop such features as bone cells, eyes, ears, nose, fingers, feet and toes. The refinement of body parts also includes teeth sockets, and the beginning of fingernails.

The budding of the clitoris, and the budding of the penis and scrotum are also taking place during the second month, but the sexual organs are not refined enough to distinguish as male or female until sometime in the third month. The extraordinary process of creation continues day after day, yet the fetus, as it is called at eight weeks, is still only two to four inches long and weighs less than one ounce. But it is already looking unmistakably human.

The Second Trimester
During the second trimester the major body systems and organs are still being refined. Facial features are molded, eyebrows and eyelashes begin to appear and the eyelids can open and close. Facial expressions, such as frowning, lips that open and close and turning of the head begin to appear, but it is not clear that these gestures can be interpreted to mean anything.

The skin of the fetus is very thin and transparent, clearly showing the blood vessels lying just below. Roughly halfway through pregnancy, muscles have developed enough to allow the fetus to move its arms and legs. This is the time when a woman begins to notice the first fluttery fetal movements, a stage termed "quickening".

During the second trimester, the heartbeat of the fetus can be heard with a stethoscope and the fetus will grow rapidly, reaching approximately 2 pounds in weight and 14 inches in length.

The Third Trimester
During the third trimester it is typical for the fetus to toss and kick quite a bit, making its presence obvious to the mother. These movements are a sign that the nerve fibers of the fetus are developing properly. They are necessary for muscular and skeletal growth, and for the development of fine motor ability.

In the seventh month and the first part of the eighth the fetus gains weight and grows tremendously. It generally triples in weight and increases in length by 5 or 6 inches. The expectant mother's abdomen becomes exceedingly large toward the end of pregnancy and may cause some back pain and frequent urination due to the fetus applying pressure to the mother's bladder.

In the eighth and ninth months the baby's organs and structures are developed enough to function on their own. During the final month of pregnancy the baby, who has been in an upright position, gradually turns completely over until its head is pointing downward. It is then ready to be born, as soon as contractions of the uterus begin to push the baby out through the vaginal canal and into the waiting world.

Miscarriage
Sometimes complications arise during pregnancy. One common complication is miscarriage. Miscarriage is the spontaneous separation and discharge through the vagina of a developing fetus before it is ready to be born. Miscarriage seems to be the body's natural solution to a pregnancy that is not developing properly. Most miscarriages occur early in the first trimester and it is estimated that about 20 percent of all pregnancies end in miscarriage.

Early miscarriages are usually not physically painful. The main signs are cramping and bleeding, much like a heavy menstrual flow. Medical care following an early miscarriage is recommended in order to insure that all of the fetal tissue is removed form the woman's body. Because there is a risk of infection if some tissue remains, a doctor may suggest a procedure called dilation and curettage (D&C) to remove it.

It is estimated that 75 percent of all miscarriages occur during the first trimester of pregnancy. The remainder occurs in the second trimester. Any fetus passed out of the body after the end of the second trimester (24th week) is called a premature birth.

Signs of second trimester miscarriage are severe, labor-like cramps and heavy bleeding followed by the discharge of the developing fetus. Medical attention is required to be certain that all fetal tissue has passed out of the body.

Generally an egg and sperm dividing or implanting improperly cause miscarriages. Sometimes a woman's hormonal level is lower than necessary, causing the lining of the uterus to weaken and to become unable to hold a fertilized egg. Often, however, the exact cause of miscarriage remains unknown.

In the majority of cases, having a miscarriage does not affect a woman's ability to get pregnant again. Miscarriage at any stage of pregnancy can be an emotionally difficult experience for couples. It is very common to experience sadness, depression, and a sense of loss as a couple's feelings of joy and hope about the pregnancy turn to loss, grief, and often feelings of blame and guilt. Providing each other with support or seeking support from other couples who have experienced a miscarriage, or from a professional, are healthy ways to help work through the feelings resulting from experiencing a miscarriage.

Ectopic Pregnancy
Another pregnancy complication is an ectopic pregnancy. An ectopic pregnancy is the growth of the fertilized egg outside the uterus. They usually occur in a Fallopian tube (which is why they are referred to as a "tubal pregnancy"). On rare occasion a fertilized egg can implant in a woman's abdomen, in an ovary, or in the cervix.

Ectopic pregnancies result in the death of the fetus and can be fatal to the mother as well. They may cause sudden bursting of the Fallopian tube, massive internal bleeding, sharp pain and weakness resulting from the loss of blood. These problems typically occur late in the first trimester, usually between the eighth and twelfth weeks.

An ectopic pregnancy may show as a "positive pregnancy test" and a physician may not see any early signs of abnormality when examining the woman. Typical signs of ectopic pregnancy are pain and cramping on the lower right or left side of the abdomen, bleeding through the vagina, weakness, dizziness or fainting (signs of internal bleeding) and a regular period, even after a pregnancy has been detected.

If any of these signs appear, a non-intrusive ultrasound examination can show whether the fetus is growing in the uterus or elsewhere. Surgery is usually performed as soon as the condition is diagnosed to avoid the possible bursting of a Fallopian tube and heavy bleeding that can seriously harm the mother.

Intervention generally involves the removal of the burst Fallopian tube, though sometimes the tube can be repaired. After such surgery a woman can still become pregnant, but her chances will be reduced by the absence of one tube. Also, a woman's chances of having another ectopic pregnancy increase after having one such pregnancy.

Toxemia
Toxemia is another relatively common pregnancy complication. Also known as pre-eclampsia, toxemia is a condition that occurs in some women during the fifth or sixth month of pregnancy.

The cause of toxemia is uncertain, but many doctors believe poor nutrition is a large contributor. Symptoms of toxemia include weight gain and rising blood pressure, then swelling of the hands and ankles due to water retention, abdominal pain, headache and poor vision.

Toxemia affects the developing baby because the placenta does not do its job properly, resulting in a smaller baby, premature delivery or delivery by caesarian. Toxemia can be managed through rest and a properly balanced diet with the avoidance of excess salt. Toxemia must be treated and monitored by a physician because if left unchecked it could lead to the death of the fetus and even the mother.

Emotional Changes
Pregnancy can be both a scary and a joyous time for a woman and her partner. The changes that pregnancy brings are not only physical but deeply emotional. Depending on the circumstances of the pregnancy (whether it is wanted or not), it may bring up feelings of confusion, denial or anger; or it may lead to emotional growth, maturity and a special feeling of completeness, despite periods of moodiness and feeling low that accompany many pregnancies.

It is not uncommon for pregnant women to feel unhappy about the changes in their bodies as pregnancy progresses. Nor is it unheard of for men to feel jealous, neglected and resentful of the great amount of attention and interest their wives receive during pregnancy. With good communication and a loving relationship these feelings usually pass without leaving a residue of major problems about the self or the marriage.

Relationship Changes
The powerful feelings aroused in both women and men as a result of pregnancy may result in a change in their relationship. For some it may be an unhappy change, particularly if an unplanned pregnancy affects finances, living space, employment or responsibilities. The stress may be felt by one partner or by both and resolution should be attempted via communication, honesty, and working at adjusting together throughout the pregnancy.

In many cases pregnancy brings a couple closer together. The excitement of becoming a family together and the anticipation of being a mother or a father may create a different sense of responsibility toward each other and foster a level of love and warmth not previously experienced.

Sexual Activity Changes
Pregnancy often has an influence on a couple's sexual activity, although it has no uniform effect on sexual feelings or function. Some women find that pregnancy is a time of heightened sexual awareness and pleasure, whereas others notice no change or a decline in sexual feelings.

Variations in sexual functioning are also found during different stages of pregnancy. Not surprisingly, women with morning sickness and high levels of fatigue during the first trimester often have neither the interest nor the energy to be sexually active.

Heightened Sexuality
The second trimester is a time when women may notice heightened sexuality both in terms of desire and physical response.

In the last trimester some couples find that a bulging belly makes sexual intercourse difficult; for others adjustments in sexual positions or non-coital sex solves this problem. Some couples agree to voluntarily abstain from sexual activity near the end of pregnancy because of concern about injuring the baby.

Though there is usually little danger of injuring the fetus or the mother, it is best to follow the advice of a doctor who has been treating the woman throughout her pregnancy regarding safe sexual practices at all stages of pregnancy.