Prenatal tests help you — and your doctor — know what’s going on
By the editors of Healthy Pregnancy magazine
You probably haven’t thought about taking tests since you left the classroom behind. Guess what — they’re back, and the high anxiety you experienced over algebra and the SATs is going to seem like nothing compared to that from some of these prenatal exams. To be sure, there are plenty of little tests you’ll barely notice, but others serve an important role in guiding you and your doctor throughout your pregnancy. You’ll wait for the results of all that poking and prodding with bated breath. Rest assured that the large majority 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, so you’ll want to talk carefully with your partner and physician about which ones are right for you. Here’s a rundown of the most common tests, and factors to consider.
Initial Laboratory Tests
When As soon as pregnancy is confirmed
Purpose A blood test is done to determine your blood type; screen for anemia, hepatitis B, and sexually transmitted diseases; and check that you are immune to rubella (German measles). A Pap smear is necessary if you haven’t had one according to your usual schedule, to check for cancerous cells in your cervix. And your urine will continue to be tested at each checkup for the appropriate protein and sugar levels and to detect any urinary tract infection.
Method Blood is drawn, a urine sample is taken, and a Pap smear is done.
Who Has It All pregnant women
Side Effects None
Results Urine, immediately; blood test and Pap smear, within a few days
Ultrasound
When Anytime throughout pregnancy, but often around the 20-week midpoint
Purpose Early in pregnancy, ultrasound can check the baby’s heart rate, confirm fetal age and due date, and diagnose multiple fetuses. It is also used to screen for abnormalities, monitor high-risk pregnancies, and check the position of the fetus and placenta. If the genitals are visible, the baby’s gender can also be confirmed.
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.
Who Has It Most women, although ACOG does not recommend routine ultrasound for all patients
Side Effects None
Results Immediate
Chorionic Villus Sampling (CVS)
When Between 10 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 disease
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 tested
Who Has It 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
Side Effects 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 it’s performed earlier than 10 weeks of gestation
Results Two to three weeks
Maternal Serum Screening
When Between 15 and 22 weeks Purpose To screen for levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol. The combination of these three tests indicates possible risk of Down syndrome and neural tube defects, such as spina bifida and anencephaly. Any such indications will need to be confirmed by further follow-up tests, such as ultrasound or amniocentesis
Method Blood test
Who Has It Offered to all women, but is optional
Side Effects Technically none, but false positives are common. Only 1 or 2 women in 100 who have abnormal levels will actually be carrying a baby who has Down syndrome, for example. False positives cause unnecessary anxiety and may result in an amniocentesis that may not have otherwise been required
Results Within one to two weeks
Amniocentesis
When Between 15 and 18 weeks
Purpose To detect Down syndrome, neural tube defects, and a number of genetic and chromosomal disorders. It also confirms gender
Method A small sample of amniotic fluid is taken with a long, thin needle, through the abdomen. It is then tested in a lab
Who Has It 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
Side Effects One woman in 200 may have a miscarriage that would otherwise not occur
Results Up to three weeks
Glucose Screening
When Between 24 and 28 weeks
Purpose To assess the risk of gestational diabetes
Method The mother drinks a sweet glucose drink supplied by her doctor, then a blood sample is drawn from her arm exactly one hour later and sent to a lab for testing
Who Has It Most women, but particularly those who are over 30, are obese, or who have a family history of diabetes
Side Effects None, but the ultrasweet drink can taste unpleasant and cause light-headedness
Results Within a few days
Non-stress Test
When After 28 weeks
Purpose To monitor the baby’s heartbeat in response to its own movement (the heartbeat should quicken with activity)
Method A fetal monitor placed on the mother’s abdomen picks up sound waves and then produces a printout of the fetal heart rate
Who Has It Women with such pregnancy complications as preeclampsia (pregnancy-induced hypertension) or gestational diabetes
Side Effects None
Results Immediate
Biophysical Profile
When Around 28 weeks
Purpose To determine the well-being of the fetus by evaluating fetal movement, heart rate, muscle tone, breathing patterns, and the level of amniotic fluid and by performing a non-stress test
Method A combination of ultrasound and heart-rate monitoring
Who Has It Women with such complications as preeclampsia or gestational diabetes
Side Effects None
Results Immediate
Group B Strep
When Between 35 and 37 weeks, or during labor
Purpose To check for Group B streptococcus (GBS), a common genital bacterium that, when present, can be passed to the baby during delivery and cause severe illness or even death
Method Prior to delivery, a culture may be taken from the vagina or rectum for testing. Treatment is delayed until labor, during which time antibiotics are administered. Antibiotics are also recommended for preterm labor and fever during labor and when a previous child has been infected with GBS
Who Has It All women or those at high risk
Side Effects None
Results Within a few days (from a culture); treatment with antibiotics is delayed until labor
Healthy Pregnancy Magazine, October 2000
By the editors of Healthy Pregnancy magazine
You probably haven’t thought about taking tests since you left the classroom behind. Guess what — they’re back, and the high anxiety you experienced over algebra and the SATs is going to seem like nothing compared to that from some of these prenatal exams. To be sure, there are plenty of little tests you’ll barely notice, but others serve an important role in guiding you and your doctor throughout your pregnancy. You’ll wait for the results of all that poking and prodding with bated breath. Rest assured that the large majority 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, so you’ll want to talk carefully with your partner and physician about which ones are right for you. Here’s a rundown of the most common tests, and factors to consider.
Initial Laboratory Tests
When As soon as pregnancy is confirmed
Purpose A blood test is done to determine your blood type; screen for anemia, hepatitis B, and sexually transmitted diseases; and check that you are immune to rubella (German measles). A Pap smear is necessary if you haven’t had one according to your usual schedule, to check for cancerous cells in your cervix. And your urine will continue to be tested at each checkup for the appropriate protein and sugar levels and to detect any urinary tract infection.
Method Blood is drawn, a urine sample is taken, and a Pap smear is done.
Who Has It All pregnant women
Side Effects None
Results Urine, immediately; blood test and Pap smear, within a few days
Ultrasound
When Anytime throughout pregnancy, but often around the 20-week midpoint
Purpose Early in pregnancy, ultrasound can check the baby’s heart rate, confirm fetal age and due date, and diagnose multiple fetuses. It is also used to screen for abnormalities, monitor high-risk pregnancies, and check the position of the fetus and placenta. If the genitals are visible, the baby’s gender can also be confirmed.
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.
Who Has It Most women, although ACOG does not recommend routine ultrasound for all patients
Side Effects None
Results Immediate
Chorionic Villus Sampling (CVS)
When Between 10 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 disease
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 tested
Who Has It 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
Side Effects 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 it’s performed earlier than 10 weeks of gestation
Results Two to three weeks
Maternal Serum Screening
When Between 15 and 22 weeks Purpose To screen for levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol. The combination of these three tests indicates possible risk of Down syndrome and neural tube defects, such as spina bifida and anencephaly. Any such indications will need to be confirmed by further follow-up tests, such as ultrasound or amniocentesis
Method Blood test
Who Has It Offered to all women, but is optional
Side Effects Technically none, but false positives are common. Only 1 or 2 women in 100 who have abnormal levels will actually be carrying a baby who has Down syndrome, for example. False positives cause unnecessary anxiety and may result in an amniocentesis that may not have otherwise been required
Results Within one to two weeks
Amniocentesis
When Between 15 and 18 weeks
Purpose To detect Down syndrome, neural tube defects, and a number of genetic and chromosomal disorders. It also confirms gender
Method A small sample of amniotic fluid is taken with a long, thin needle, through the abdomen. It is then tested in a lab
Who Has It 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
Side Effects One woman in 200 may have a miscarriage that would otherwise not occur
Results Up to three weeks
Glucose Screening
When Between 24 and 28 weeks
Purpose To assess the risk of gestational diabetes
Method The mother drinks a sweet glucose drink supplied by her doctor, then a blood sample is drawn from her arm exactly one hour later and sent to a lab for testing
Who Has It Most women, but particularly those who are over 30, are obese, or who have a family history of diabetes
Side Effects None, but the ultrasweet drink can taste unpleasant and cause light-headedness
Results Within a few days
Non-stress Test
When After 28 weeks
Purpose To monitor the baby’s heartbeat in response to its own movement (the heartbeat should quicken with activity)
Method A fetal monitor placed on the mother’s abdomen picks up sound waves and then produces a printout of the fetal heart rate
Who Has It Women with such pregnancy complications as preeclampsia (pregnancy-induced hypertension) or gestational diabetes
Side Effects None
Results Immediate
Biophysical Profile
When Around 28 weeks
Purpose To determine the well-being of the fetus by evaluating fetal movement, heart rate, muscle tone, breathing patterns, and the level of amniotic fluid and by performing a non-stress test
Method A combination of ultrasound and heart-rate monitoring
Who Has It Women with such complications as preeclampsia or gestational diabetes
Side Effects None
Results Immediate
Group B Strep
When Between 35 and 37 weeks, or during labor
Purpose To check for Group B streptococcus (GBS), a common genital bacterium that, when present, can be passed to the baby during delivery and cause severe illness or even death
Method Prior to delivery, a culture may be taken from the vagina or rectum for testing. Treatment is delayed until labor, during which time antibiotics are administered. Antibiotics are also recommended for preterm labor and fever during labor and when a previous child has been infected with GBS
Who Has It All women or those at high risk
Side Effects None
Results Within a few days (from a culture); treatment with antibiotics is delayed until labor
Healthy Pregnancy Magazine, October 2000
