Pregnancy - Prenatal diagnosis and tests

During your pregnancy, you will undergo a few or many of the following examinations. Depending on your health and potential health risks, these tests may be performed more than once; some may be done each month. Other tests may be added. Each provides you and the physician with information about your health and the health of the developing baby. Prenatal care increases the chances of having a healthy baby tremendously. Less than 2 percent of the women who see their obstetrician regularly after the second month of pregnancy have an underweight baby.

Home Pregnancy Tests

Home pregnancy tests can now be purchased in almost any pharmacy or drugstore. The prices range from $5.00 to more than $20.00. All the tests work on the same principle—they test for the presence of the hormone Human Chorionic Gonadotropin (HCG), which is present at high levels during pregnancy. A chemical in the home testing kit will change colors when HCG is present. The tests are 99 percent accurate in labs, but probably around 95 percent accurate in home use, where circumstances are not as controlled. A false-negative test will register if the HCG levels are not high enough yet. A false-positive reading may occur if you have unusually high HCG readings or another chemical which mimics HCG in the test. If you have not had your period and you suspect that you may be pregnant, it is advisable to have a doctor's test regardless of the results of the home kit. You should seek medical advice as soon as possible.

Blood tests

Blood is tested during your first examination to determine if you are pregnant. Either during the same examination or at a follow-up examination, blood is tested for the following: anemia; infectious diseases, including sexually transmitted diseases and AIDS; immunities to childhood diseases, especially German measles; and diabetes. Sometime before delivery blood will be checked again for diabetes, sexually transmitted diseases, and hepatitis.

Rh Compatibility Test

Rh is the part of the blood type that labels the blood positive or negative. The only time this poses a problem is when the mother is Rh negative and the father is Rh positive and the offspring develops Rh positive blood. This used to pose serious threat to the pregnancy, but can now be treated adequately with drugs.

Urine tests

The physician will check your urine, probably at each visit, for sugar (diabetes), protein (toxemia), bacteria (infection), and perhaps drug use.

Pelvic Exams

Pelvic exams are done throughout pregnancy to check the position of the fetus and the status of the vaginal walls and the cervix. As you approach delivery, the cervix muscle will efface and dilate , meaning that the walls will thin and the cervical opening will increase. During your early visits to the doctor, a pap smear will be performed to check for infections and unusual growths on the cervix. Other smear tests will be done for diseases such as chlamydia. These tests may be repeated late in pregnancy.

Ultrasound

By using sound waves to reflect off the fetus in the uterus, the doctor is able to determine the size, position, and occasionally the sex of the forming baby. Ultrasound can be performed anytime after about the fifth week of pregnancy. Your physician will let you know what scheduling is used in his or her office. Some obstetricians perform ultrasound to get an accurate date on the pregnancy by the size of the fetus; others may wait to do one reading later to determine general position and health.

Ultrasonography is performed transabdominally (across the stomach) or transvaginally (through the vagina). If the ultrasound is done transabdominally, then the woman must drink plenty of fluids beforehand to fill the bladder. This allows the bladder to push the uterus up for better positioning as well as provide an obvious sighting for the bladder so it is not misidentified.

Amniocentesis

To determine the genetic makeup of the developing baby, a small portion of the amniotic fluid can be drawn out of the womb to pick up floating cells, which contain the baby's genetic information. This allows the doctor and the pregnant woman the opportunity to screen for different inheritable diseases. Amniocentesis is usually performed on higher risk patients during the fourth or fifth month of pregnancy. Armed with the information provided, the parents can choose to carry the baby to term, abort the fetus, or have intrauterine surgery performed to remedy problems with the fetus.

The fluid is drawn out by a syringe that is inserted into the woman's naval to the level of the uterus. Using ultrasound to avoid the placenta and the fetus, the needle draws uo fluid.

This procedure runs about a one in one hundred risk of causing amniotic leaking, and a one in two hundred risk of infection. The risk of triggering spontaneous abortion is even lower.

Chorionic Villus Sampling (CVS)

A newer procedure than the amniocentesis, the CVS samples the tissue that forms between the interior uterine wall and the beginning placenta. The needle-like tube is inserted either through the vagina or the stomach and guided by ultrasound to the chorionic villus. This testing procedure is usually performed during the third month of pregnancy.

The benefits of the test are that it can be performed earlier in the pregnancy, and a determination to discontinue the pregnancy poses less risk to the woman when decided during the first trimester. Amniocentesis can only be done after the start of the second trimester. The risk is that, because it is a newer procedure, the spontaneous abortion rate following CVS is higher than the rate for amniocentesis. As doctors become more practiced with the procedure it is believed the rate will even out.

Fetal Monitoring

External and internal monitoring of the fetus are done to check on the heart rate and stress of the fetus. External monitoring involves registering the heartbeat via ultrasound readings and, if needed, a pressure gauge to measure contractions.

Internal monitoring is done only during delivery and if some level of distress is suspected or likely in the fetus. The monitoring electrode is placed on the baby's scalp through the opening in the cervix. This can only be done after dilation has started. A catheter that measures pressure can also be inserted into the uterus to measure contraction pressure. Both of these units can be connected to the monitor reader by cord or by radio wave.

Monitoring is now a regular procedure during delivery. It allows the doctors to check on the health of the baby and provides an early warning if the baby is in distress. It should be set up so that it does not interfere at all with the birthing process.

Apgar Test Score

When the baby is born, you will probably be given an Apgar score that refers to the general health of the baby. The scores range from 0 to 10 and are based on five criteria: skin color and appearance, heart rate, respiratory effort, muscle tone, and reflex responses. Stillborns rate a zero with no pulse, blue skin, and no response system; extremely healthy babies can score a 10 with good coloration, good crying, and strong pulse and muscular activity.