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A pregnancy is divided into three phases, called trimesters. Each trimester has its own significant milestones. The first trimester is the most fragile period, during which all major organs and systems are formed. Most birth defects and miscarriages occur during the first trimester. During the second and third trimester, the fetus is fully formed and grows and matures rapidly. The trimesters are divided as follows:
• First trimester : 0 - 12 weeks
• Second trimester : 12 - 24 weeks
• Third trimester : 24 - 40 weeks
(However, some authorities use the 42 weeks method divided by 3 trimesters with the 1st trimester, 0 - 13 weeks; the 2nd trimester, 14 - 28 weeks; and the 3rd trimester, 29 - 42 weeks.)
Listed in the directory below, you will find additional information regarding the three phases of pregnancy, for which we have provided a brief overview.
The First Trimester (0-12 Weeks)
The Pregnant Mother
The Second Trimester (13-28 Weeks)
The Third Trimester (29-40 Weeks)
Anatomy: Fetus in Utero
Finding Out You're Pregnant
The First Trimester (0-12 Weeks)
The first prenatal visit:
The first prenatal visit is the most thorough. A complete medical history is taken, a physical examination is conducted, as well as certain tests and procedures are performed to assess the initial health of the mother and the embryo. The first prenatal visit may include the following:
• Personal medical history - this may include taking record of any of the following:
o previous and current medical conditions - such as diabetes, high blood pressure (hypertension), anemia, and/or allergies
o current medications - prescription and over-the-counter
o previous surgeries
• maternal and paternal family medical history - including illnesses such as diabetes or mental retardation, and genetic disorders such as sickle-cell disease or Tay-Sachs disease
• personal gynecological and obstetrical history - including past pregnancies - stillbirths, miscarriage, deliveries, terminations - and menstrual history (i.e., length and duration of menstrual periods)
• education - including a discussion regarding the importance of proper nutrition, regular exercise, the avoidance of alcohol, drugs, and tobacco during pregnancy, and a discussion of any concerns about domestic violence
• pelvic examination - this type of examination may be performed for one/all of the following reasons:
o to note the size and position of the uterus
o to determine the age of the fetus
o to check the pelvic bone size and structure
o to perform a Pap test (also called Pap smear) to detect the presence of abnormal cells
• laboratory tests - including the following:
o urine tests - to screen for bacteria, sugar, and protein
o blood tests - to determine blood type
o All pregnant women are tested for the Rh factor during the early weeks of pregnancy.
A mother and fetus may have incompatible blood types, the most common is Rh incompatibility. Rh incompatibility occurs when the mother's blood is Rh-negative and the father's blood is Rh-positive and the fetus' blood is Rh-positive. The mother may produce antibodies against the Rh-positive fetus which may lead to anemia in the fetus. Incompatibility problems are monitored and appropriate medical treatment is available to prevent the formation of Rh antibodies during pregnancy.
o blood screening tests - to detect diseases (i.e., rubella, also called German measles)
o genetic tests - to detect inherited diseases (i.e., sickle-cell anemia, Tay-Sachs disease)
o screening tests - to detect infectious diseases (i.e., sexually transmitted diseases)
The first prenatal visit is also an opportunity to ask any questions or discuss any concerns that you may have about your pregnancy.
What to expect during the first trimester:
A healthy first trimester is crucial to the normal development of the fetus. The mother-to-be may not be showing much on the outside, but inside her body all the major body organs and systems of the fetus are forming.
As the embryo implants itself into the uterine wall, several developments take place, including:
• Amniotic sac
A sac filled with amniotic fluid, called the amniotic sac, surrounds the fetus throughout the pregnancy. The amniotic fluid is liquid made by the fetus and the amnion (the membrane that covers the fetal side of the placenta) that protects the fetus from injury and helps regulate the temperature of the fetus.
• Placenta
The placenta is an organ shaped like a flat cake that only grows during pregnancy. It attaches to the uterine wall with tiny projections called villi. Fetal blood vessels grow from the umbilical cord into these villi, exchanging nourishment and waste products with the mother's blood. The fetal blood vessels are separated from the mother's blood supply by a thin membrane.
• Umbilical cord
The umbilical cord is a rope-like cord connecting the fetus to the placenta. The umbilical cord contains two arteries and a vein, which carry oxygen and nutrients to the fetus and waste products away from the fetus.
It is during this first trimester that the fetus is most susceptible to damage from substances such as alcohol, drugs, certain medications, and illnesses such as rubella (German measles).
During the first trimester, both the mother's body and the fetus are changing rapidly.
Fetal development during the first trimester:
The most dramatic changes and development occur during the first trimester. During the first eight weeks, a fetus is called an embryo. The embryo develops rapidly and by the end of the first trimester it becomes a fetus that is fully formed, weighing approximately 1/2 to one ounce and measuring, on average, three to four inches in length.
First trimester growth and development benchmarks:
Just as each child grows and matures at different rates and at different times, so does that same child as it begins its life in the womb. The chart provided below provides benchmarks for most normal pregnancies. However, each fetus develops differently.
by the end of 4 weeks
• all major systems and organs begin to form
• the embryo looks like a tadpole
• the neural tube (which becomes the brain and spinal cord), the digestive system, and the heart and circulatory system begin to form
• the beginnings of the eyes and ears are developing
• tiny limb buds appear (which will develop into arms and legs)
• the heart is beating
by the end of 8 weeks
• all major body systems continue to develop and function, including the circulatory, nervous, digestive, and urinary systems
• the embryo is taking on a human shape, although the head is larger in proportion to the rest of the body
• the mouth is developing tooth buds (which will become baby teeth)
• the eyes, nose, mouth, and ears are becoming more distinct
• the arms and legs are clearly visible
• the fingers and toes are still webbed but can be clearly distinguished
• the main organs continue to develop and you can hear the baby's heartbeat using an instrument called a Doppler
• the bones begin to develop and the nose and jaws are rapidly developing
• the embryo is in constant motion but cannot be felt by the mother from embryo to fetus After 8 weeks, the embryo is now referred to as a fetus (which means offspring).
Although the fetus is only 1 to 1 1/2 inches long at this point, all major organs and systems have been formed.
during weeks 9-12
• the external genital organs are developed
• fingernails and toenails appear
• eyelids are formed
• fetal movement increases
• the arms and legs are fully formed
• the voice box (larynx) begins to form in the trachea
The fetus is most vulnerable during the first 12 weeks. During this period of time, all of the major organs and body systems are forming and can be damaged if the fetus is exposed to drugs, German measles, radiation, tobacco, and chemical and toxic substances.
Even though the organs and body systems are fully formed by the end of 12 weeks, the fetus cannot survive independently.
Changes in the mother's body:
During pregnancy, many changes are also occurring in the mother-to-be's body. Women experience these changes differently. Some symptoms of pregnancy continue for several weeks or months, while others are only experienced for a short period of time. Some women experience many symptoms, while other women experience only a few or none at all. The following is a list of changes and symptoms that may occur during the first trimester.
What are Kegel exercises?
Kegel exercises are pelvic floor exercises that help tone the muscles in the vagina and perineum, which is important for delivery. Conditioned muscles will make the birthing process easier. In addition, these exercises, when done after delivery, can help to speed up the recovery process. Doing a Kegel exercise is simple:
1. Tighten the muscles around your vagina and anus. (The exercise is similar to stopping urination midstream.)
2. Hold the muscles tightened as long as you can, working up to 8 to 10 seconds each time.
3. Relax the muscles.
4. Tighten and relax the muscles several times a day.
• The mammary glands enlarge causing the breasts to swell and become tender in preparation for breastfeeding. This is due to an increased amount of the hormones estrogen and progesterone. A supportive bra should be worn.
• A woman's areolas (the pigmented areas around each breast's nipple) will enlarge, darken, and may become covered with small, white bumps called Montgomery's tubercles (enlarged sweat glands).
• Veins become more prominent on the surface of the breasts.
• The uterus is growing and begins to press on the woman's bladder, causing the need for her to urinate more frequently.
• Partly due to surges in hormones, a pregnant woman may experience mood swings similar to premenstrual syndrome (a condition experienced by some women that is characterized by mood swings, irritability, and other physical symptoms that occur shortly before each menstrual period).
• Increased levels of hormones to sustain the pregnancy may cause "morning sickness," which is feelings of nausea and sometimes vomiting. However, morning sickness does not necessarily occur just in the morning and rarely interferes with proper maternal and fetal nutrition.
• Constipation may occur as the growing uterus presses on the rectum and intestines.
• The muscular contractions in the intestines, which help to move food through the digestive tract, are slowed due to high levels of progesterone. This may, in turn, cause heartburn, indigestion, constipation, and gas.
• Clothes may feel tighter around the breasts and waist, as the size of the abdomen begins to increase to accommodate the growing fetus.
• A woman may experience fatigue due to the physical and emotional demands of pregnancy.
• Cardiac volume increases by approximately 40 to 50 percent from the beginning to the end of the pregnancy, causing an increased cardiac output. An increased cardiac output may cause an increased pulse rate during pregnancy. The increase in blood volume is needed for extra blood flow to the uterus.
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The Second Trimester (13-28 Weeks)
Prenatal visits during the second trimester:
During the second and third trimester prenatal visits, your physician may check the following, depending on your current medical condition and the health of the fetus:
• any current symptoms or discomforts
• mother's weight
• mother's blood pressure
• urine test - to detect albumin (a protein) which may indicate preeclampsia or toxemia, and sugar (which may indicate hyperglycemia)
• growth, size, and development of the fetus
• size of the uterus - after approximately 12 weeks of gestation, the uterus can be felt through the abdominal wall
• height of the fundus (top of the uterus)
• fetal heartbeat
What to expect during the second trimester:
The second trimester marks a turning point for mother and fetus. The mother usually begins to feel better and will start showing the pregnancy more. The fetus has now developed all its organs and systems and will now focus on growing in size and weight.
During the second trimester, the umbilical cord continues to thicken as it carries nourishment to the fetus. However, harmful substances also pass through the umbilical cord to the fetus, so care should be taken to avoid alcohol, tobacco, and other known hazards.
During the second trimester, both the mother's body and the fetus continue to grow.
Fetal development during the second trimester:
Now that all the major organs and systems have formed in the fetus, the following six months will be spent growing. The weight of the fetus will multiply more than seven times over the next few months, as the fetus becomes a baby that can survive outside of the uterus.
By the end of the second trimester, the fetus will be about 13 to 16 inches long and weighs about 2 to 3 pounds. Fetal development during the second trimester includes the following:
• The fetus kicks, moves, and can turn from side to side.
• The eyes have been gradually moving to the front of the face and the ears have moved from the neck to the sides of the head. The fetus can hear the mother's voice.
• A creamy white substance (called vernix caseosa, or simply vernix) begins to appear on the fetus and helps to protect the thin fetal skin. Vernix is gradually absorbed by the skin, but some may be seen on babies even after birth.
• The fetus is developing reflexes such as swallowing and sucking.
• The fetus can respond to certain stimuli.
• The placenta is fully developed.
• The brain will undergo its most important period of growth from the 5th month on.
• Fingernails have grown on the tips of the fingers and toes, and the fingers and toes are fully separated.
• The fetus goes through cycles of sleep and wakefulness.
• Skin is wrinkly and red, covered with soft, downy hair (called lanugo).
• Hair is growing on the head of the fetus.
• Fat begins to form on the fetus.
• Eyelids are beginning to open and the eyebrows and eyelashes are visible.
• Fingerprints and toeprints have formed.
• Rapid growth is continuing in fetal size and weight.
• The 20th week marks the halfway point of the pregnancy.
A fetus born at the end of 24 weeks may survive in a neonatal intensive care unit.
Changes in the mother's body:
The second trimester is the most physically enjoyable for most women. Morning sickness usually abates by this time and the extreme fatigue and breast tenderness usually subsides. These changes can be attributed to a decrease in levels of human chorionic gonadotropin (hCG) hormone and an adjustment to the levels of estrogen and progesterone hormones.
The following is a list of changes and symptoms that may occur during the second trimester:
• Appetite may increase.
• The mother may be able to feel the movement of the fetus for the first time - a phenomenon called quickening - by 20 weeks.
• The uterus has grown to the height of the belly button, making the pregnancy visible.
• The skin on the belly may itch as it grows and there may be pain down the sides of the body as the uterus stretches. The lower abdomen may ache as ligaments stretch to support the uterus.
• The need to frequently urinate may decrease as the uterus grows out of the pelvic cavity, relieving pressure on the bladder.
• A mother's nose may become congested and she may experience nosebleeds. This is due to the increase in hormones (estrogen and progesterone) that affect the mucous membranes in the nose.
• A woman's gums become more spongy and may bleed easily. This is due to the increase in hormones (estrogen and progesterone) that affect the mucous membranes in the mouth.
• Varicose veins and hemorrhoids may appear.
• A woman may have a white-colored vaginal discharge called leukorrhea. (A colored or bloody discharge may signal possible complications and should be examined immediately.)
• The increasing weight gain may cause backaches.
• Skin pigmentation may change on the face or abdomen due to the pregnancy hormones.
• Heart burn, indigestion, and constipation may continue.
The Third Trimester (29-40 Weeks)
Prenatal visits during the third trimester:
During the second and third trimester prenatal visits, your physician may check the following, depending on your current medical condition and the health of the fetus:
• any current symptoms or discomforts
• mother's weight
• mother's blood pressure
• urine test - to detect albumin (a protein) which may indicate preeclampsia or toxemia, and sugar (which may indicate hyperglycemia)
• position, growth, and development of the fetus
• height of the fundus (top of the uterus)
• fetal heartbeat
After approximately the 29th week, your physician may change the schedule of your prenatal visits from monthly to every two weeks. After approximately the 36th week, your prenatal visits may be scheduled once every week. This schedule will depend upon the medical condition of the mother-to-be, the growth and development of the fetus, and your physician's preference.
Toward the later weeks of the pregnancy (started at approximately the 38th week), a pelvic examination will be performed to determine the dilation and effacement of the cervix. Your physician will also ask about Braxton-Hicks contractions and discuss labor and delivery procedures.
What to expect during the third trimester:
The third trimester marks the home stretch, as the mother-to-be prepares for the delivery of her baby. The fetus is continuing to grow in weight and size and the body systems finish maturing. The mother may feel more uncomfortable now as she continues to gain weight and begins to have false labor contractions (called Braxton-Hicks contractions).
During the third trimester, it is a good idea to start taking childbirth classes in preparation for the big day - especially in the case of first pregnancies. If you plan to breastfeed, taking a breastfeeding class may be helpful.
During the third trimester, both the mother's body and fetus continue to grow and change.
Fetal development during the third trimester:
During the third trimester, the fetus continues to grow in size and weight. The lungs are still maturing and the fetus begins to position itself head-down. By the end of the third trimester, the fetus is about 19 to 21 inches long and weighs, on average, six to nine pounds. Fetal development during the third trimester includes:
• The fetus can see and hear.
• The brain continues to develop.
• The kidneys and lungs continue to mature.
• By the 36th week, the head may "engage" (drop into the pelvic area) - a process called "lightening."
• The bones of the skull remain soft to make it easier to pass through the birth canal.
• For many babies, the irises of the eyes are slate blue. The permanent eye color will not appear until several days or weeks after birth.
• The fetus can suck its thumb and has the ability to cry.
• By 38 to 40 weeks, the fetus' lanugo has disappeared almost completely.
• By 38 to 40 weeks, the lungs have matured completely.
• The baby is covered in vernix caseosa (or simply called vernix), a creamy, protective coating on the skin.
• The head will usually turn downward during the last couple of weeks of pregnancy.
Changes in the mother's body:
In the third trimester, some women become increasingly uncomfortable as their due date nears. As the fetus grows in size and crowds the abdominal cavity, some mothers-to-be have difficulty taking deep breaths or getting comfortable at night for sleep, while others are free from any discomfort as they anxiously await the arrival of their new son or daughter.
The following is a list of changes and symptoms that a woman may experience during the third trimester and includes:
• Increased skin temperature as the fetus radiates body heat, causing the mother to feel hot.
• The increased urinary frequency returns due to increased pressure being placed on the bladder.
• Blood pressure may decrease as the fetus presses on the main vein that returns blood to the heart.
• Swelling of the ankles, hands, and face may occur (called edema), as the mother continues to retain fluids.
• Hair may begin to grow on a woman's arms, legs, and face due to increase hormone stimulation of hair follicles. Hair may also feel courser.
• Leg cramps may become more frequent.
• Braxton-Hicks contractions (false labor) may begin to occur at irregular intervals in preparation for childbirth.
• Stretch marks may appear on the abdomen, breast, thighs, and buttocks.
• Colostrum (a fluid in the breasts that nourishes the baby until the breast milk ecomes available) may begin to leak from the nipples.
• Dry, itchy skin may persist, particularly on the abdomen, as the skin continues to grow and stretch.
• A woman's libido (sexual drive) may decrease.
• Skin pigmentation may become more apparent, especially dark patches of skin on the face.
• Constipation, heartburn, and indigestion may continue.
• Increased white-colored vaginal discharge (leukorrhea) which may contain more mucus.
• Backaches may persist and increase in intensity.
• Hemorrhoids may persist and increase in severity.
• Varicose veins in the legs may persist and increase in severity.
As demonstrated above, each woman carries her baby differently, depending upon her body structure and amount of weight gain.
Finding Out You're Pregnant
What are the signs of pregnancy?
The signs of pregnancy vary from woman to woman. Usually the most obvious sign is the absence of menstruation (amenorrhea). However, some women continue to have bleeding even while pregnant. The following are the most common initial signs of pregnancy. However, each woman may experience the signs of pregnancy differently. These may include:
• fatigue
• sore and swollen breasts
• nausea or vomiting (also called morning sickness)
• frequent urination
• certain food cravings or aversions
• bloating of the abdomen
• darkening of the skin around the nipples (also called the areola)
• bluish-purple vaginal and cervical tissue, due to blood engorgement, which can be detected during a pelvic examination.
These early signs may not positively indicate pregnancy, but may actually signal another process occurring within the body. A pregnancy test can provide more accurate results.
What is a pregnancy test?
Pregnancy is confirmed with a pregnancy test. A pregnancy test can be performed on either urine or blood. Pregnancy tests detect the presence of human chorionic gonadotropin hormone (hCG), a hormone produced by the placenta about 10 days after fertilization. Levels of the hCG hormone approximately double every two days during the first 60 days of pregnancy. Pregnancy tests that are performed using the woman's blood are done by a physician and are usually performed to obtain a very early diagnosis of pregnancy or also to confirm an at-home pregnancy test. Blood tests are very accurate and can detect pregnancy by the second week after conception.
Women can conduct an at-home pregnancy test by testing a sample of urine about two weeks after conception. Home pregnancy tests have become more accurate in the last decade. Urine tests, in general, are usually 97 percent accurate if the result is positive, indicating that you are pregnant. However, if the test result is negative and no menstrual period resumes, a pregnancy test should be repeated one week later.
Always consult your physician to confirm a positive at-home pregnancy test with a more reliable pregnancy test and physical examination.
Contraception / Birth Control
What is birth control?
Birth control refers to any activity, medication, or equipment used to prevent pregnancy. There are many types of birth control available for women who do not wish to become pregnant. The decision on which method is right for you should be made with your physician, as well as with your partner.
Birth control methods work in different ways to prevent pregnancy, including the following:
• creating a barrier that blocks sperm from reaching the egg
• killing sperm
• preventing eggs from being released by the ovaries
• changing the cervical mucus to hinder sperm from moving into the uterus
• altering the tissue lining the uterus so that a fertilized egg cannot implant
What are the different types of birth control?
Some methods that do not require a prescription from your physician include the following:
• Abstinence - not having sexual intercourse.
• Spermicides - foams or creams placed inside the vagina to kill sperm; these may also provide some protection against sexually transmitted diseases, especially when used with a latex condom.
• Male condoms - a thin tube made of latex or a natural material that is placed over the penis. The sperm is collected in the end of the condom. Latex condoms may provide some protection against sexually transmitted diseases.
• Female condoms - a liner made of latex or natural material that is placed inside the vagina. Latex condoms may provide some protection against sexually transmitted diseases.
• natural family planning - timing intercourse to avoid "fertile" days using various methods of monitoring body temperature, watching for changes in cervical mucus, and the use of ovulation prediction kits. This method, often known as the "rhythm" method, has a high risk for pregnancy.
Some methods that require a visit to your physician for an examination and a prescription include the following:
• Oral contraceptives (birth control pills) - medications taken daily that prevent ovulation by controlling pituitary hormone secretion. Usually, oral contraceptives contain the hormones estrogen and progestin. Some types are progestin-only.
In addition to prevention of pregnancy, oral contraceptives have several health benefits including regulating menstrual cycles and decreasing the amount and length of menstrual periods. This can help increase iron stores in women with iron deficiency associated with excessive bleeding. Prevention of certain ovarian and endometrial cancers is a significant benefit of the use of oral contraceptives. Some research has found that some benign (non-cancerous) breast diseases, including fibroadenoma and cystic changes, occur less frequently with the use of oral contraceptives. Recent studies have also suggested that
oral contraceptive use may reduce the occurrence of severe disabling rheumatoid arthritis.
• Norplant - capsules containing the synthetic hormone levonorgestrel, implanted under the skin in the upper arm of a woman, which continuously prevent the ovaries from releasing an egg for up to five years. Anesthesia is required for insertion and removal of this type of birth control.
• Depo-Provera - a progesterone-like drug given by injection to prevent pregnancy by stopping ovulation. The effects last for about three months and another injection must be given to continue birth control effectiveness.
• MPA/E2C - a new type of contraceptive that combines two types of hormones, estrogen and progestin, in a monthly injection. These hormones work to prevent ovulation and continue regular menstrual periods. The injection must be repeated every 28 to 33 days to be effective.
• Diaphragm or cervical cap - a dome-shaped rubber cup with a flexible rim that is inserted through the vagina to cover the cervix. This type of birth control must be inserted prior to having sexual intercourse.
• Intrauterine device (IUD) - devices placed in the uterus through the cervix by a physician. The IUD works by preventing an egg from being fertilized in the tubes or from attaching to the wall of the uterus. IUDs containing hormones must be replaced annually, while copper IUDs can last up to 10 years.
Surgery that results in the inability to become pregnant includes the following:
• hysterectomy - removal of the uterus and usually the ovaries and fallopian tube. This is a permanent form of birth control.
• tubal ligation or tubal occlusion ("tying the tubes") - surgery to cut, cauterize, or band the fallopian tubes to prevent the egg from being transported to the uterus. Tubal ligation is designed to be a permanent method of birth control. Although certain types of tubal ligations can be reversed, the reversal procedure may not be successful.
• vasectomy - cutting or clamping the vas deferens, the tubes that carry the sperm from the testes - are blocked. The testes still produce sperm, but the sperm die and are absorbed by the body. This is a permanent male birth control measure.
Methods that have been suggested as preventive, but may actually present a high risk for pregnancy include the following:
• Withdrawal before ejaculation
• Sexual intercourse during menstruation
• Standing up immediately after sexual intercourse
• Douching after sexual intercourse
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