Overview of Prenatal Testing

Over the course of your pregnancy, your doctor will keep track of your progress and the baby’s development. During these office visits, there are several routine prenatal tests you may have to insure that you and your baby are in good health.

Many aspects of pregnancy and childbirth have changed in the past few generations. My grandmother gave birth to both of my aunts at home in bed in the 1930s and had never seen a doctor in her life until she begrudgingly allowed herself to be carted off to the hospital for my mother’s birth. My mother-in-law smoked throughout her pregnancy. Her obstetrician, like many in the 1950s, didn’t even allow her to come in for her first prenatal visit until she was well into her second trimester. When it was discovered that she was slightly anemic, doctor’s orders were that she drink red wine every night after dinner because it was “good for the blood.” She gave birth to my husband under general anesthesia while the father-to-be chain-smoked in the hospital waiting room.

Before we get too sentimental about “the good ol’ days” of prenatal ignorance, remember that as early as a half century ago, childbirth was still considered potentially dangerous or life threatening for the mother and frequently resulted in the death of the newborn. Birth defects—many of them severe—were a common occurrence, and because there was little understanding of chromosomal or genetic abnormalities, superstition led many people to ostracize parents of “abnormal” children.

Today, the availability of proper prenatal care and testing has significantly reduced many of the risks of childbirth, and because of early screening and diagnostic tests, parents are given a chance to prepare themselves for the possibility that their child might be born disabled and to educate themselves about their options.

With accurate over-the-counter pregnancy tests, women today can find out they are pregnant even before they miss a period, so proper prenatal care may begin right from the start, and women can reduce the risks of exposure to teratogenic substances (agents that can cause malformations of an embryo or fetus) in early pregnancy, when the embryo is most vulnerable.

If you are just beginning the journey to motherhood, rest assured that your chances of having a healthy baby are better now than at any point in history. Over the course of your pregnancy, your doctor will want to see you monthly, bi-weekly, and then weekly to keep track of your progress and the baby’s development. During these office visits, there are several routine prenatal tests that he or she will perform to insure that you and your baby are in good health.

Laboratory Blood Tests

Over the course of your pregnancy, your doctor will periodically test your blood to determine things like your blood type (A, B, AB, or O), your hemoglobin and blood sugar levels, whether or not your RH factor is positive or negative, and your immunity to Rubella and chickenpox. The doctor may also perform a screening to test for Hepatitis.

Women whose RH factors are negative need to be treated to protect their babies from a possibly dangerous blood disorder, and those with a low red blood cell or hemoglobin count will be treated for anemia, which could increase the risk of pre-term delivery.

Urine Tests

It is common for expecting women to provide urine samples at their prenatal visits. Sugar found in a pregnant woman’s urine could be indicative of gestational diabetes, a potentially dangerous condition that needs to be monitored carefully throughout the pregnancy.

Those with protein in their urine may need to be checked for a urinary-tract infectionpreeclampsia, or pregnancy-induced high blood pressure, all of which can be serious medical conditions that require treatment and monitoring.


Most doctors today use routine ultrasounds to help them determine things such as the presence of multiple fetuses, the position of the placenta, the due date of the baby, and birth defects, as well as to keep track of fetal growth.

Targeted ultrasounds may help doctors evaluate specific organs that are at risk for genetic abnormalities, and fetal echocardiograms help doctors check the fetus’ heart structure when there is a question about the possibility of fetal heart disease or abnormality.

Using a painless transducer, which bounces high frequency sound waves through the mother’s abdomen and at the fetus, the doctors are able to receive a visual image created by the echoes.

Although many studies have shown that there is no evidence to suggest that the fetus can be harmed by ultrasound, the new trend of capturing 3-D ultrasound images for non-medical purposes has some doctors concerned that the overuse of the technology may not be completely safe during pregnancy.

Triple Marker Screening

A Triple Marker test screens for the possibility of Down syndrome, measuring the amount of alpha-fetoprotein (AFP), unconjugated estriol (uEST), and Human choronic gonadotropin (hCG) in your blood.

Studies have shown that women that are carrying babies with Down syndrome have higher levels of hCG and lower levels of AFP and uEST than those carrying babies without the affliction.

These blood tests are usually performed between the 15th and 20th weeks of a pregnancy. It is important to remember that the Triple Marker test is only a screening test and is not diagnostic. If the results, which take about two weeks to become available, are abnormal, your doctor may suggest further testing, such as an amniocentesis.

Expanded Alpha-Fetoprotein (AFP)

This blood test, recommended for all pregnant women, helps to detect the possibility of neural tube defects, such as spina bifida and Down syndrome in the fetus. Like the Triple Marker screening, the AFP is not diagnostic in nature, and most women who test positive are carrying a healthy fetus (although many doctors will suggest that those who receive positive results have an amniocentesis to be sure).

Nuchal Translucency (NT)

One of the newer tests available, the NT screening helps to determine the risk of Down syndrome by using high-resolution ultrasound to examine the nuchal area (the fold of skin at the back of the neck) of the fetus. Using a numerical formula that combines the ultrasound test results with a series of blood tests and the woman’s age, the NT can detect the potential for Down syndrome in about 80 percent of women.

Because it is only a screening test, however, women who have positive results or high numbers in an NT exam are usually expected to follow up with an amniocentesis or chorionic villi sampling (CVS) test for more definitive results.


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 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 slightly less than one in 200, but the test has a very high accuracy rate for detecting up to 95 percent of neural tube defects. As a result, women who are over 35 or have a family history of chromosomal 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, Genital Herpes, Chlamydia, and Trichomoniasis 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. GBS bacteria, usually present in your gastrointestinal tract, 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.

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