You probably haven't thought about taking tests since you left the classroom behind. Guess what  -- they're back, and the high anxiety you felt in school is going to seem like nothing compared with what you'll feel during some of these prenatal exams. To be sure, there are plenty you'll barely notice, but others hold information about your baby's health that's vital for you and your care provider. You'll wait for the results of all that poking and prodding with bated breath. Rest assured that the vast majority of test come back just fine, indicating a glowingly healthy baby.

Keep in mind, too, that many pregnancy tests are optional, depending on your age and medical history, and some carry risks, so you'll want to discuss the options carefully with your partner and physician to decide which ones are right for you. Here's a rundown of the most common tests, and factors to consider.

Initial Blood Tests
When As soon as pregnancy is confirmed
Purpose A blood test is done to screen for anemia and hepatitis B; to check that you are immune to rubella (German measles) and chicken pox; and to determine your blood type and Rh status. The Rh factor is a protein found in red blood cells. If the mother is Rh-negative (meaning she doesn't have the protein) and the fetus is Rh-positive, the mother's body may attack the baby's red blood cells. If an Rh difference is detected, the doctor can provide shots to prevent such a reaction.
Method Blood is drawn.
Who All pregnant women
Results Within a few days

Urine Test
When First ob/gyn visit
Purpose To check for the appropriate protein and sugar levels and to detect any urinary tract infection.
Method A urine sample is taken.
Who All pregnant women
Results Immediate

Pap Smear
When First ob/gyn visit
Purpose A Pap smear is necessary if you haven't had one on your usual schedule to check for cancerous cells in your cervix.
Method A small sample of cells is taken from the cervix.
Who All pregnant women
Results Within a few days

AIDS and other sexually transmitted diseases (STDs)
When First ob/gyn visit
Purpose To test for a variety of diseases that, if untreated, can cause birth defects and pregnancy complications. It is recommended that all pregnant women be tested for HIV, the virus that causes AIDS. Most women are also screened for syphilis at the same time. You may also be tested  -- or can request it  -- for gonorrhea, chlamydia, and herpes, which can pose threats to the health and development of your baby.
Method Blood tests and swabs of the vagina and cervix
Who All pregnant women
Results Within a few days

Chorionic Villus Sampling (CVS)
When Between ten and 12 weeks
Purpose To detect chromosomal disorders, such as Down syndrome, and genetic disorders, such as sickle-cell anemia, cystic fibrosis, and Tay-Sachs
Method A sample of chorionic villi, the tiny fingerlike tissues of the placenta, is obtained either by a tube inserted through the cervix or a needle guided into the abdomen with the help of ultrasound. The sample is then sent to a lab for testing.
Who Couples at risk of or with a family history of birth defects, couples who already have a child with birth defects, or women who will be 35 or older on their due dates and who don't want to wait for amniocentesis
Results Two to three weeks
Note One woman in 100 may suffer a miscarriage that would otherwise not occur; there's also a very rare chance of limb abnormalities, particularly if the test is performed earlier than ten weeks of gestation.

Maternal Serum Screening
When Between 15 and 20 weeks, ideally 16 to 18 weeks
Purpose Also called triple screen or multiple marker, this checks your levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol. These three tests, along with the mother's age, are used to estimate possible risk of Down syndrome and neural tube defects, such as spina bifida and anencephaly. A new test can assess Down syndrome risk in the first trimester with "nuchal measurement" (take using an ultrasound of the fetal neck). If screening suggests an elevated risk, follow-up testing, such as amniocentesis, can provide answers.
Method Blood is drawn
Who Offered to all pregnant women but is optional
Results One to two weeks
[REDORANGE_TEXT_BOLD {Note}] False positives are common: Only one or two women in 100 who have abnormal levels will actually be carrying a baby who has Down syndrome. False positives can cause anxiety and may result in an unnecessary amniocentesis.

Ultrasound
When Anytime throughout pregnancy, but often around the 20-week midpoint
Purpose To monitor high-risk pregnancies, check the size and position of the fetus and placenta, and see whether you're carrying more than one child. Given the genitals are visible, the baby's gender can also be detected if you choose.
Method A device that emits high-frequency sound waves is placed on the mother's abdomen or in the vagina. The sound waves bounce off the internal tissues and produce an image of the fetus and uterine environment on a monitor for viewing. If you're having an abdominal ultrasound, a full bladder may be necessary, so you'll need to drink several glasses of water beforehand.
Who Most pregnant women, although the American College of Obstetricians and Gynecologists does not recommend routine ultrasound for all patients
Results Immediate

Amniocentesis
When Between 15 and 20 weeks
Purpose To detect Down syndrome, neural tube defects, and a number of genetic and chromosomal disorders. It also confirms the baby's gender.
Method A long, thin needle is guided through the abdomen with the help of ultrasound. A small sample of amniotic fluid is then removed and tested in a lab.
Who Women whose maternal serum screening results are abnormal, couples with a family history of genetic birth defects, and women who will be 35 or older at the time of delivery
Results Up to two weeks; new "FISH" technology takes a few days
[REDORANGE_TEXT_BOLD {Note}] Between 1 in 200 and 1 in 400 amniocentesis procedures result in a miscarriage.

Cystic Fibrosis Screening
When First or second trimester, ideally before 20 weeks
Purpose To determine whether one or both parents are carriers for cystic fibrosis (CF), a genetic disorder that causes lifelong problems with digestion and breathing. If both parents are found to be carriers, there is a 1 in 4 chance that their baby will have CF.
Method Blood test or saliva sample
Who Recommended for all expectant parents
Results Within two weeks

Glucose Screening
When Between 24 and 28 weeks
Purpose To assess the risk of gestational diabetes, which can result in an overly large baby, a difficult delivery, and in some cases, cause birth trauma
Method The mother is given a sweet glucose drink; an hour later a blood sample is drawn from her arm. The sample is then sent to a lab for testing.
Who Most pregnant women, but particularly those who are over 30, are obese, or who have a family history of diabetes
Results Within a few days

Nonstress Test
When After 28 weeks
Purpose To monitor the baby's heartbeat in response to movement
Method A fetal monitor records the baby's heart rate.
Who Women with pregnancy complications as preeclampsia or gestational diabetes
Results Immediate

Stress Test
When Usually to follow up an inconclusive nonstress test
Purpose To monitor the baby's heartbeat during and after a contraction
Method A fetal monitor picks up changes in the baby's heart rate in response to mild contractions triggered by oxytocin.
Who Same as nonstress test
Results Immediate

Biophysical Profile
When At nonstress or stress test
Purpose To monitor baby's status
Method An ultrasound checks the level of amniotic fluid and detects fetal movements, muscle tone, and breathing patterns.
Who Same as nonstress test
Results Immediate

Group B Strep
When Between 35 and 37 weeks
Purpose To check for a common genital bacterium that, when present, can be passed to the baby during delivery and, if untreated, cause severe illness or even death

Method Before delivery, a culture is taken for testing. If the results are positive, antibiotics are administered during labor. Antibiotics are also given to those experiencing preterm labor or who have a fever during labor.
Who All pregnant women or those at high risk. You may request the test.
Results Within a day or two

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