Overview of Prenatal Testing

Amniocentesis

In this brief procedure, a trans-abdominal needle is used to extract amniotic fluid from the uterus between the 16th and 20th weeks of pregnancy. Cells in the fluid are then analyzed to screen for chromosomal abnormalities such as Down syndrome, and the chemicals in the sample are analyzed for possible neural tube defects, such as spina bifida or Down syndrome.

Many women complain that the procedure is painful, although some say the sensation is equivalent to that of having blood drawn. Some doctors offer a local anesthetic to help numb the skin before inserting the hollow needle.

The rate of miscarriage associated with amniocentesis is less than one in 200, but the test has a very high accuracy rate for detecting up to 95 percent of neural tube defects and chromosomal abnormalities. As a result, women who are over 35 or have a family history of congenital abnormalities may be advised by their doctor to have an amniocentesis test.

Chorionic Villus Sampling (CVS)

In CVS sampling, a small amount of tissue is extracted from the placenta between the 10th and 12th weeks of the pregnancy to be studied for possible chromosomal abnormalities. Although this test cannot detect neural tube defects, it can be performed earlier in the pregnancy than amniocentesis, and the rate of miscarriage associated with CVS is only about one in 300.

The procedure is a brief but potentially uncomfortable. Using a hollow tube inserted either through the cervix or the abdomen, (depending upon the position of the placenta), a small portion of the chorionic villi is removed for study.

Women are told not to do strenuous exercise or travel by air for at least 72 hours following CVS or an amniocentesis. They should also refrain from sexual intercourse for 73 hours and not do any lifting over 15 pounds for the first 24 hours after the procedure. Some women may experience cramping or bleeding following either of the procedures, but these symptoms usually clear up within a day or two.

Tests for Sexual, Bacterial, and Ethnic-Related Genetic Diseases

In addition to the routine blood work, screening and diagnostic tests, there are also specific tests for genetic diseases indigenous to various ethnic backgrounds, such as Sickle Cell Anemia disease in African-Americans, Tay-Sachs in Ashkenazi Jews, Cystic Fibrosis in Caucasians, and Thalassemia in people of Asian and Mediterranean descent.

Tests for sexually transmitted diseases, such as Gonorrhea, Human Immunodeficiency Virus (HIV), Hepatitis B, Syphilis, HPV (pap), Chlamydia, Trichomoniasis and sometimes Genital Herpes, may also be recommended by your doctor, as many of these illnesses can cause complications or be passed to your baby during or after delivery. When a woman tests positive for an STD, precautions must be taken during delivery to insure the well being of the newborn.

Shortly before your due date, your doctor will perform a Group B Streptococcal Disease (GBS) test, so that antibiotics can be given to you during labor if needed. GBS bacteria, present in the gastrointestinal tract of up to 25 percent of women, can sometimes also be found in the vaginal or rectal area, and if it is not treated, it can be passed on to the newborn and possibly cause infection or neonatal death.

At-Home Testing

For those women who experience pregnancy-related anxiety in between OB-GYN visits, a simple at-home fetal movement test can often alleviate fear and convince mom-to-be that everything is going well in utero. Starting at about 28 weeks of pregnancy, you can monitor your baby’s movements by simply lying on one side—preferably after a meal—and counting how many times in a 60-minute period your baby kicks, flips, or rolls over. If you count at least ten movements in less than an hour, chances are the baby is doing well. If you don’t experience ten movements within an hour or don’t feel fetal movement for a day or more, you should contact their doctor. Although there are some conditions, such as being overweight, that can affect a woman’s ability to feel fetal movement, it’s always best to see a doctor when in doubt.

We’ve come a long way in being able to monitor the prenatal health and well-being of our babies, but even with all the available tests, ultimately the best indicator of how well your body is doing during pregnancy is you, so keep a positive attitude, and pay attention to your own body. Discuss any concerns you have with your doctor, and remember not to get too emotionally wrapped up in the results of screening tests that are odds-oriented. Even if the numbers seem to be against you, they are, after all, just numbers, and even many diagnostic examinations are not 100 percent definitive. Chances are good these days that your pregnancy is a healthy one.