pregnancy Pregnancy by alendar



       Causes and symptoms
       Key Terms

          Pregnancy usually lasts 40 weeks in humans, beginning from the first day of the
          woman's last menstrual period, and is divided into three trimesters. The illustration
          above depicts the position of the developing fetus during each trimester.
                                   (Illustration by Electronic Illustrators Group.)

The period from conception to birth. After the egg is fertilized by a sperm and then
implanted in the lining of the uterus, it develops into the placenta and embryo, and later
into a fetus. Pregnancy usually lasts 40 weeks, beginning from the first day of the
woman's last menstrual period, and is divided into three trimesters, each lasting three

Pregnancy is a state in which a woman carries a fertilized egg inside her body. Due to
technological advances, pregnancy is increasingly occurring among older women in the
United States.

First month

At the end of the first month, the embryo is about a third of an inch long, and its head and
trunk--plus the beginnings of arms and legs--have started to develop. The embryo
receives nutrients and eliminates waste through the umbilical cord and placenta. By the
end of the first month, the liver and digestive system begin to develop, and the heart starts
to beat.

Second month

In this month, the heart starts to pump and the nervous system (including the brain and
spinal cord) begins to develop. The 1 in (2.5 cm) long fetus has a complete cartilage
skeleton, which is replaced by bone cells by month's end. Arms, legs and all of the major
organs begin to appear. Facial features begin to form.

Third month

By now, the fetus has grown to 4 in (10 cm) and weighs a little more than an ounce (28
g). Now the major blood vessels and the roof of the mouth are almost completed, as the
face starts to take on a more recognizably human appearance. Fingers and toes appear.
All the major organs are now beginning to form; the kidneys are now functional and the
four chambers of the heart are complete.

Fourth month

The fetus begins to kick and swallow, although most women still can't feel the baby
move at this point. Now 4 oz (112 g), the fetus can hear and urinate, and has established
sleep-wake cycles. All organs are now fully formed, although they will continue to grow
for the next five months. The fetus has skin, eyebrows, and hair.

Fifth month

Now weighing up to a 1 lb (454 g) and measuring 8-12 in (20-30 cm), the fetus
experiences rapid growth as its internal organs continue to grow. At this point, the mother
may feel her baby move, and she can hear the heartbeat with a stethoscope.

Sixth month

Even though its lungs are not fully developed, a fetus born during this month can survive
with intensive care. Weighing 1-1.5 lbs (454-681 g), the fetus is red, wrinkly, and
covered with fine hair all over its body. The fetus will grow very fast during this month
as its organs continue to develop.
Seventh month

There is a better chance that a fetus born during this month will survive. The fetus
continues to grow rapidly, and may weigh as much as 3 lb (1.3 kg) by now. Now the
fetus can suck its thumb and look around its watery womb with open eyes.

Eighth month

Growth continues but slows down as the baby begins to take up most of the room inside
the uterus. Now weighing 4-5 lbs (1.8-2.3 kg) and measuring 16-18 in (40-45 cm) long,
the fetus may at this time prepare for delivery next month by moving into the head-down

Ninth month

Adding 0.5 lb (227 g) a week as the due date approaches, the fetus drops lower into the
mother's abdomen and prepares for the onset of labor, which may begin any time between
the 37th and 42nd week of gestation. Most healthy babies will weigh 6-9 lb (2.7-4 kg) at
birth, and will be about 20 in. long.

Causes and symptoms
The first sign of pregnancy is usually a missed menstrual period, although some women
bleed in the beginning. A woman's breasts swell and may become tender as the mammary
glands prepare for eventual breastfeeding. Nipples begin to enlarge and the veins over the
surface of the breasts become more noticeable.

Nausea and vomiting are very common symptoms and are usually worse in the morning
and during the first trimester of pregnancy. They are usually caused by hormonal
changes, in particular, increased levels of progesterone. Women may feel worse when
their stomach is empty, so it is a good idea to eat several small meals throughout the day,
and to keep things like crackers on hand to eat even before getting out of bed in the

Many women also feel extremely tired during the early weeks. Frequent urination is
common, and there may be a creamy white discharge from the vagina. Some women
crave certain foods, and an extreme sensitivity to smell may worsen the nausea. Weight
begins to increase.

In the second trimester (13-28 weeks) a woman begins to look noticeably pregnant and
the enlarged uterus is easy to feel. The nipples get bigger and darker, skin may darken,
and some women may feel flushed and warm. Appetite may increase. By the 22nd week,
most women have felt the baby move. During the second trimester, nausea and vomiting
often fade away, and the pregnant woman often feels much better and more energetic.
Heart rate increases as does the volume of blood in the body.
By the third trimester (29-40 weeks), many women begin to experience a range of
common symptoms. Stretch marks may develop on abdomen, breasts, and thighs, and a
dark line may appear from the navel to pubic hair. A thin fluid may be expressed from the
nipples. Many women feel hot, sweat easily and often find it hard to get comfortable.
Kicks from an active baby may cause sharp pains, and lower backaches are common.
More rest is needed as the woman copes with the added stress of extra weight. Braxton
Hicks contractions may get stronger.

At about the 36th week in a first pregnancy (later in repeat pregnancies), the baby's head
drops down low into the pelvis. This may relieve pressure on the upper abdomen and the
lungs, allowing a woman to breathe more easily. However, the new position places more
pressure on the bladder.

A healthy gain for most women is between 25 and 35 pounds. Women who are
overweight should gain less; and women who are underweight should gain more. On
average, pregnant women need an additional 300 calories a day. Generally, women will
gain three to five pounds in the first three months, adding one to two pounds a week until
the baby is born. An average, healthy full-term baby at birth weighs 7.5 lb (3.4 kg), and
the placenta and fluid together weigh another 3.5 lb. The remaining weight that a woman
gains during pregnancy is mostly due to water retention and fat stores. Her breasts, for
instance, gain about 2 lb. in weight, and she gains another 4 lb due to the increased blood
volume of pregnancy.

In addition to the typical, common symptoms of pregnancy, some women experience
other problems that may be annoying, but which usually disappear after delivery.
Constipation may develop as a result of food passing more slowly through the intestine.
Hemorrhoids and heartburn are fairly common during late pregnancy. Gums may become
more sensitive and bleed more easily; eyes may dry out, making contact lenses feel
painful. Pica (a craving to eat substances other than food) may occur. Swollen ankles and
varicose veins may be a problem in the second half of pregnancy, and chloasma may
appear on the face.

Chloasma, also known as the "mask of pregnancy" or melasma, is caused by hormonal
changes that result in blotches of pale brown skin appearing on the forehead, cheeks, and
nose. These blotches may merge into one dark mask. It usually fades gradually after
pregnancy, but it may become permanent or recur with subsequent pregnancies. Some
women also find that the line running from the top to the bottom of their abdomen
darkens. This is called the linea nigra.

While the above symptoms are all considered to be normal, there are some symptoms that
could be a sign of a more dangerous underlying problem. A pregnant woman with any of
the following signs should contact her doctor immediately:

      abdominal pain
      rupture of the amniotic sac or leaking of fluid from the vagina
      bleeding from the vagina
      no fetal movement for 24 hours (after the fifth month)
      continuous headaches
      marked, sudden swelling of eyelids, hands, or face during the last three months
      dim or blurry vision during last three months
      persistent vomiting

Many women first discover they are pregnant after a positive home pregnancy test.
Pregnancy urine tests check for the presence of human chorionic gonadotropin (hCG),
which is produced by a placenta. The newest home tests can detect pregnancy on the day
of the missed menstrual period.

Home pregnancy tests are more than 97% accurate if the result is positive, and about 80%
accurate if the result is negative. If the result is negative and there is no menstrual period
within another week, the pregnancy test should be repeated. While home pregnancy tests
are very accurate, they are less accurate than a pregnancy test conducted at a lab. For this
reason, women may want to consider having a second pregnancy test conducted at their
doctor's office to be sure of the accuracy of the result.

Blood tests to determine pregnancy are usually used only when a very early diagnosis of
pregnancy is needed. This more expensive test, which also looks for hCG, can produce a
result within nine to 12 days after conception.

Once pregnancy has been confirmed, there are a range of screening tests that can be done
to screen for birth defects, which affect about 3% of unborn children. Two tests are
recommended for all pregnant women: alpha-fetoprotein (AFP) and the triple marker test.

Other tests are recommended for women at higher risk for having a child with a birth
defect. This would include women over age 35, who had another child or a close relative
with a birth defect, or who have been exposed to certain drugs or high levels of radiation.
Women with any of these risk factors may want to consider amniocentesis, chorionic
villus sampling (CVS) or ultrasound.

Other prenatal tests

There are a range of other prenatal tests that are routinely performed, including:

      PAP test
      gestational diabetes screening test at 24-28 weeks
      tests for sexually transmitted diseases
      urinalysis
      blood tests for anemia or blood type
      screening for immunity to various diseases, such as German measles
Prenatal care is vitally important for the health of the unborn baby. A pregnant woman
should be sure to eat a balanced, nutritious diet of frequent, small meals. Women should
begin taking 400 mcg of folic acid several months before becoming pregnant, as folic
acid has been shown to reduce the risk of spinal cord defects, such as spina bifida.

No medication (not even a nonprescription drug) should be taken except under medical
supervision, since it could pass from the mother through the placenta to the developing
baby. Some drugs, called teratogens, have been proven harmful to a fetus, but no drug
should be considered completely safe (especially during early pregnancy). Drugs taken
during the first three months of a pregnancy may interfere with the normal formation of
the baby's organs, leading to birth defects. Drugs taken later on in pregnancy may slow
the baby's growth rate, or they may damage specific fetal tissue (such as the developing
teeth), or cause preterm birth.

To have the best chance of having a healthy baby, a pregnant woman should avoid:

      smoking
      alcohol
      street drugs
      large amounts of caffeine
      artificial sweeteners


Women should begin following a healthy diet even before they become pregnant. This
means cutting back on high-calorie, high-fat, high-sugar snacks, and increasing the
amount of fruits, vegetables and whole grains in her diet. Once she becomes pregnant,
she should make sure to get at least six to 11 servings of breads and other whole grains,
three to five servings of vegetables, two to four servings of fruits, four to six servings of
milk and milk products, three to four servings of meat and protein foods, and six to eight
glasses of water. She should limit caffeine to no more than one soft drink or cup of coffee
per day.

Pregnancy is a natural condition that usually causes little discomfort provided the woman
takes care of herself and gets adequate prenatal care. Childbirth education classes for the
woman and her partner help prepare the couple for labor and delivery.

There are many ways to avoid pregnancy. A woman has a choice of many methods of
contraception which will prevent pregnancy, including (in order of least to most

        spermicide alone
        natural (rhythm) method
        diaphragm or cap alone
        condom alone
        diaphragm with spermicide
        condom with spermicide
        intrauterine device (IUD)
        contraceptive pill
        sterilization (either a man or woman)
        avoiding intercourse

A substance produced by a fetus' liver that can be found in the amniotic fluid and in the mother's blood.
Abnormally high levels of this substance suggests there may be defects in the fetal neural tube, a structure
that will include the brain and spinal cord when completely developed. Abnormally low levels suggest the
possibility of Down' syndrome.
Braxton Hicks' contractions
Short, fairly painless uterine contractions during pregnancy that may be mistaken for labor pains. They
allow the uterus to grow and help circulate blood through the uterine blood vessels.
A skin discoloration common during pregnancy, also known as the "mask of pregnancy" or melasma, in
which blotches of pale brown skin appear on the face. It is usually caused by hormonal changes. The
blotches may appear in the forehead, cheeks, and nose, and may merge into one dark mask. It usually fades
gradually after pregnancy, but it may become permanent or recur with subsequent pregnancies. Some
women may also find that the line running from the top to the bottom of their abdomen darkens. This is
called the linea nigra.
An unborn child during the first eight weeks of development following conception (fertilization with
sperm). For the rest of pregnancy, the embryo is known as a fetus.
An unborn child from the end of the eights week after fertilization until birth.
Human chorionic gonadotropin (hCG)
A hormone produced by the placenta during pregnancy.
The organ that develops in the uterus during pregnancy that links the blood supplies of the mother and
Rhythm method
The oldest method of contraception with a very high failure rate, in which partners periodically refrain from
having sex during ovulation. Ovulation is predicted on the basis of a woman's previous menstrual cycle.
Spina bifida
A congenital defect in which part of the vertebrae fail to develop completely, leaving a portion of the spinal
cord exposed.


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