Throughout your pregnancy, you'll want to know how your baby is growing. You'll also want to know if how you're feeling is normal. Prenatal tests can offer you valuable information about your health and the health of your growing child.
If your doctor recommends a screening or test, be sure to learn about the risks and benefits. Most parents agree that prenatal tests offer them peace of mind while helping to prepare them for their baby's arrival. But it's your choice to accept or decline a test.
Read on to learn about tests that may be available to you during your third trimester.
Your first visit to the obstetrician should have included a full physical, urine test, and blood test to check for things like:
After the first visit, you can expect to get your urine tested and your weight and blood pressure checked at every (or almost every) visit until you deliver. The reason for this is to identify conditions such as gestational diabetes and preeclampsia.
Between your 35th and 37th weeks of pregnancy, the doctor will check you for group B streptococcus (GBS) infection. GBS bacteria are found naturally in the vaginas of many women but can cause serious infections in newborns. This test involves swabbing the vagina and rectum. A woman whose test comes back positive must go to the hospital as soon as labor begins so that intravenous (IV) antibiotics can be started to reduce the chance of the baby being infected with this illness.
Throughout your third trimester, you'll be offered more tests depending on your age, health, family medical history, and other factors.
Glucose screening checks for gestational diabetes, a short-term form of diabetes that develops in some women during pregnancy. Gestational diabetes can cause health problems for the baby, especially if it is not diagnosed or treated.
Most women have this test, and if they have gestational diabetes, are treated to reduce the risk to the baby.
Screening for gestational diabetes usually is done at 24 to 28 weeks. Testing may be done earlier for women who are at higher risk for it, such as those who:
This test involves drinking a sugary liquid and then having your blood drawn after an hour. If the sugar level in the blood is high, you'll have a glucose-tolerance test, which means you'll drink a glucose solution on an empty stomach and have your blood drawn once every hour for 3 hours.
The results are usually available within 1 to 2 days. Ask if your health care provider will call you with the results if they are normal or only if the reading is high and you need to come in for another test.
A nonstress test (NST) can determine if the baby is responding normally to a stimulus. It is used mostly in high-risk pregnancies or when a health care provider is uncertain of a baby's movements, and usually can be performed after 26 weeks. This is when a baby's heart rate can appropriately respond by speeding up or slowing down.
This test may also be done if you've gone beyond your due date. The NST can help a doctor make sure that the baby is receiving enough oxygen and is responding to stimulation. However, an unresponsive baby isn't necessarily in danger, though further testing might be needed.
Sometimes, a biophysical profile (BPP) is done, which includes an ultrasound and an NST. A BPP examines a baby's breathing, movement, amount of amniotic fluid, and tone, in addition to the heart rate response.
Your health care provider may recommend this if you have a high-risk pregnancy, if there are concerns during your pregnancy, or if you have a low-risk pregnancy but are past your due date.
An NST may be recommended any time after 26 to 28 weeks, depending on why it is needed.
The health care provider will measure the response of the fetus' heart rate to each movement the fetus makes as reported by the mother or observed by the doctor on an ultrasound screen. If the fetus doesn't move during the test, he or she may be asleep and the health care provider may use a buzzer to wake the baby. You also may be asked to drink or eat to try to stimulate the baby more.
Ultrasounds were once used only in high-risk pregnancies but have become so common that they're often part of routine prenatal care.
During an ultrasound, sound waves are bounced off the baby's bones and tissues to construct an image showing the baby's shape and position in the uterus. Also called a sonogram, sonograph, echogram, or ultrasonogram, ultrasounds are used to:
This test is considered safe, but it's up to you to decide whether you want to undergo it. Talk to your health care provider to find out why this test is recommended for you.
Ask your doctor when you will need to have an ultrasound. Women with high-risk pregnancies may need to have multiple ultrasounds throughout their third trimester to make sure a baby is developing normally.
Sometimes, when a doctor is uncertain of a baby's movements, a biophysical profile (BPP) is done, which can include an ultrasound and a nonstress test (NST). A BPP examines a baby's breathing, movement, amount of amniotic fluid, and tone, in addition to the heart rate response.
Although the technician can see the images immediately, a full evaluation by a doctor may take up to 1 week if one is not on site during the exam.
Depending on where you have the ultrasound done, the technician may be able to tell you that day whether everything looks OK. However, most radiology centers or health care providers prefer that technicians not comment until a specialist has taken a look — even when everything is OK.
This test stimulates the uterus with pitocin, a synthetic form of oxytocin (a hormone secreted during childbirth), to determine the effect of contractions on fetal heart rate. It may be recommended when a nonstress test or biophysical profile indicates a problem and can determine whether the baby's heart rate remains stable during contractions.
This test may be ordered if the nonstress test or biophysical profile indicates a problem. However, it can induce labor.
Your doctor may schedule it if he or she is concerned about how the baby will respond to contractions or feels that it is the appropriate test to determine the fetal heart rate response to a stimulus.
Mild contractions are brought on either by injections of pitocin or by squeezing the mother's nipples (which causes oxytocin to be secreted). The fetus' heart rate is then monitored.
Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: January 2014
|Maternal and Child Health Bureau This U.S. government agency is charged with promoting and improving the health of mothers and children.|
|American Pregnancy Association This national organization promotes reproductive and pregnancy wellness.|
|American College of Obstetricians and Gynecologists (ACOG) This site offers information on numerous health issues. The women's health section includes readings on pregnancy, labor, delivery, postpartum care, breast health, menopause, contraception, and more.|
|American College of Nurse-Midwives (ACNM) The ACNM supports the practice of midwifery through research, accreditation of midwife education programs, and establishment of clinical practice standards.|
|Group B Strep and Pregnancy Women who have this common but potentially dangerous bacteria while pregnant receive antibiotics during labor to avoid passing the bacteria onto their babies.|
|Pregnancy & Newborn Center Advice and information for expectant and new parents.|
|Medical Care During Pregnancy The sooner in pregnancy good care begins, the better for the health of both moms and their babies. Here's what to expect.|
|FAQs: Prenatal Tests Find out what tests are available to keep you informed of your -- and your baby's -- health throughout pregnancy.|
|Are Ultrasound "Snapshots" of Your Unborn Baby a Good Idea? A shop in your local shopping center offers ultrasounds for pregnant women. It seems convenient, but are there risks involved? Here's what experts say.|
|When Your Baby Has a Birth Defect If your child has a birth defect, you don't have to go it alone - lots of people and resources are available to help you.|
|All About Genetics Read the basics about genetics, including how certain illnesses, or increased risks for certain illnesses, pass from generation to generation.|
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