by Mary Abreu

A pregnancy test is just the first of many such tests a pregnant woman will take during those 40 weeks. Unfamiliar words and acronyms – AFP, chorionic villi sampling, glucose tolerance – are uttered by medical professionals, sometimes with little explanation of what they mean. Here’s a handy guide for helping decipher the sometimes-confusing code of prenatal testing.
 

Alpha-fetoprotein test
(also called maternal serum alpha-fetoprotein screening)

When it’s performed: Between 16-18 weeks
Recommended for: All moms-to-be, but especially women 35 and older, those with a family history of birth defects, diabetics and women who used potentially harmful medications or drugs during pregnancy.

How it’s done: A blood sample is drawn from the mother-to-be’s arm and sent to a lab to analyze the high and low levels of AFP. Other factors – maternal age and ethnicity, among others – are taken into consideration as well.

What it does: Unlike other tests, the AFP is purely a screening tool. It does not diagnose any problems; it merely estimates the chances of an abnormality, based on a variety of factors. A doctor may recommend further testing, including diagnostic ultrasound and amniocentesis, if the screening shows a high risk of genetic or chromosomal abnormalities or neural tube defects.

Any risks or side effects? No.

Amniocentesis

When it’s performed: 14-20 weeks

Recommended for: Parents-to-be with family medical histories of chromosome abnormalities (like Down syndrome) or other inherited disorders (such as cystic fibrosis). A woman may be referred for an amniocentesis if other, less invasive testing indicates the possibility of certain fetal issues.
How it’s done: A needle, guided by ultrasound, is inserted through the abdomen to take a sample of amniotic fluid. The fluid contains cells shed by the fetus, which are analyzed by a lab. Results may be back in a few days or as much as two weeks.

What it does: Like CVS, amniocentesis is used to diagnose inherited and genetic disorders. It can detect neural tube defects, usually spina bifida.

Any risks or side effects? There is a risk of miscarriage associated with amniocentesis, about 1 in 400 among facilities that regularly perform the test. There also is the potential for the needle to come in contact with the baby. Women may have cramping, leaking amniotic fluid and soreness around the puncture site following the procedure.

Blood test

When it’s performed: Usually at the first prenatal exam

Recommended for: All moms-to-be

How it’s done: A small sample of blood will be taken from the arm. Depending on the insurance and provider, this may be performed in the doctor’s office or at a hospital lab.

What it does: The test determines blood type, Rh factor, glucose, iron and hemoglobin levels. The doctor also will check for rubella, sexually transmitted diseases and toxoplasmosis (an infection related to cleaning a cat’s litter box). If you have a family history of genetic diseases – cystic fibrosis, sickle-cell anemia or Tay-Sachs disease, to name a few – a blood test can also determine whether your child may be affected.

Any risks or side effects? No

Chorionic villus sampling (CVS)

When it’s performed: 10-13 weeks

Recommended for: Parents-to-be with family medical histories of chromosome abnormalities (like Down syndrome) or other inherited disorders (such as cystic fibrosis).

How it’s done: The doctor will insert a thin catheter through the cervix to the placenta, using ultrasound to guide it. Some of the placenta’s chorionic villi cells are sucked into the catheter.

What it does: CVS is a diagnostic test that can reveal chromosome abnormalities and other inherited disorders. It can be performed earlier in pregnancy than other, similar tests, and it provides results in one to seven days. CVS does not test for neural tube defects.

Any risks or side effects? This is an invasive test and has some risk to the baby. One out of every 100 procedures results in miscarriage. Following the procedure, the mother may have spotting, cramping and pain, and infection.

Glucose challenge screening / Glucose tolerance test

When it’s performed: 26-28 weeks

Recommended for: All moms-to-be undergo glucose challenge screening; women who test positive during the screening take the glucose tolerance test

How it’s done: For the screening, the mother-to-be will drink a super-sweet liquid, then have blood drawn one hour later. If she is referred for the glucose tolerance test, her doctor will provide some dietary guidelines, including fasting 14 hours prior to the test. Blood is drawn to determine the fasting blood glucose level, and then the mother will drink even more of the glucose liquid. Blood will then be drawn and tested every hour during a three-hour span.

What it does: Determines whether the mom-to-be has gestational diabetes.

Any risks or side effects? No. However, because of the fasting and sugar-loading required with the glucose tolerance test, it’s probably wise to have someone else drive.

Group B Strep (GBS) infection screening

When it’s performed: 35-37 weeks

Recommended for: All moms-to-be

How it’s done: The doctor will swab the patient’s vagina and rectum. That sample is then grown into a culture and examined for GBS. Results usually are back within 48 hours.

What it does: The GBS bacteria can be found in 15-40 percent of all healthy, adult women. Because a mother can pass GBS to her baby during delivery, the test is performed to determine whether the baby is at risk. If so, she may get intravenous antibiotics during delivery to protect the baby. A newborn infected with GBS may suffer from breathing or kidney problems, meningitis, pneumonia and other problems. Approximately 1 in every 100-200 babies born to GBS-positive mothers becomes ill.

Any risks or side effects? No.

Ultrasound

When it’s performed: As early as the first prenatal visit to establish gestational age; more commonly at 20 weeks

Recommended for: All moms-to-be

How it’s done: A special machine uses high-frequency sound waves to scan the abdomen. The resulting “picture” shows details about the baby, placenta, uterus and cervix. An ultrasound can be performed with a special probe, inserted vaginally (usually in the early stages of pregnancy) or with a transducer rubbed over the abdomen.

What it does: Ultrasound is used as a diagnostic tool, letting your doctor check for any fetal developmental issues, verify due dates, measure amniotic fluid levels and check the location of the placenta.

Any risks or side effects? This is a noninvasive procedure; however, the long-term effect of repeated ultrasounds on the developing fetus is not known. Because of this, doctors recommend ultrasound be used only when it’s medically necessary.

Urinalysis

When it’s performed: Every prenatal visit

Recommended for: All moms-to-be

How it’s done: At each visit, the doctor will collect a urine sample in a sterile plastic cup.

What it does: A test strip dipped into the sample checks for high levels of sugar (a possible sign of gestational diabetes), protein (possible kidney infection), ketones (a sign of dehydration) and bacteria (potential urinary tract infection).

Any risks or side effects? No