Routine tests help keep close tabs on you and your baby. That’s why it’s so important to keep all your prenatal appointments. Screening tests can spot potential problems early.
These tests usually include:
History and physical exam. During your first or second prenatal visit, you’ll answer a lot of questions about your health and family history. This information helps the doctor know whether you have any specific risks to address, such as an inherited genetic disorder. You will also have a physical exam. Your doctor will calculate your due date based on the date of your last menstrual period.
Pelvic exam and Pap smear. Prenatal testing during the first trimester begins with a pelvic exam and Pap smear to check the health of your cervical cells. This testing screens for cervical cancer and for certain sexually transmitted diseases (STDs).
Blood tests. During one of your first visits, your doctor or midwife will identify your blood type and Rh (rhesus) factor, screen for anemia, check for immunity to rubella (German measles), and test for hepatitis B, syphilis, and HIV and other STDs.
Depending on racial, ethnic, or family background, you may be offered tests and genetic counseling to assess risks for diseases such as Tay-Sachs, cystic fibrosis, and sickle cell anemia (if these weren't done at a preconception visit). Testing for some of these diseases can also be done with saliva.
You might be tested for exposure to diseases such as toxoplasmosis and varicella (the virus that causes chickenpox. Your health care provider may also want to check your levels of hCG, a hormone secreted by the placenta, and progesterone, a hormone that helps maintain the pregnancy.
Urine tests. You will also be asked early on for a urine sample so that your doctor or midwife can look for signs of kidney infection and, if necessary, can confirm your pregnancy by measuring the hCG level. (A blood hCG test to confirm pregnancy may be used instead.) Urine samples will be collected regularly to spot glucose (a sign of diabetes) and protein, which could show preeclampsia, a pregnancy-induced disease marked by high blood pressure.
In the later part of the first trimester you will be offered genetic testing. Some people feel like these tests may cause them undue stress, and they prefer to make sure the baby is genetically normal after delivery. Others want all the testing they can get, realizing that these tests sometimes are not 100% accurate. Talk with your doctor or with a genetic counselor about the pros and the cons before you decide. There are different genetic testing options that involve blood tests alone or with an ultrasound that involve no risk to the fetus. If these noninvasive tests are abnormal, you might have further tests.
One first semester genetic test combines a blood test with an ultrasound to screen for Down syndrome. It may be available between 11 and 14 weeks of pregnancy. The results of a blood test that measures hCG and PAPP-A (pregnancy-associated plasma protein A) in maternal blood are used with an ultrasound measurement of the skin at the back of the fetus’ neck (called nuchal translucency). The procedure may be able to spot many Down syndrome cases and other genetic conditions. However, as with all screening methods, a more invasive diagnostic technique like CVS is used if results are positive.
Noninvasive prenatal testing (NIPT). This cell-free fetal DNA test can be done as early as after 10 weeks of pregnancy. The test uses a blood sample to measure the relative amount of free fetal DNA in a mother's blood. It's thought that the test can detect 99% of all Down syndrome pregnancies. It also tests for some other chromosomal abnormalities.
Chorionic villus sampling (CVS). If you're 35 or older, have a family history of certain diseases, or have had a positive result on noninvasive genetic tests, you will be offered this invasive test, usually between 10 and 12 weeks of pregnancy. CVS can detect many genetic defects, such as Down syndrome, sickle cell anemia, cystic fibrosis, hemophilia, and muscular dystrophy. The procedure involves threading a tiny catheter through your cervix or inserting a needle into your abdomen to get a tissue sample from the placenta. The procedure carries a 1% risk of inducing miscarriage and is about 98% accurate in ruling out certain chromosomal birth defects. But, in contrast to amniocentesis, it does not help in detecting neural tube disorders, such as spina bifida and anencephaly, or abdominal wall defects.
Be sure to discuss all of your testing options with your doctor so that together you can decide on the ones that will be best for you.
If you’re expecting twins, it’s a high-risk pregnancy. For this reason, your doctor will want to watch you and your babies closely. You'll have all the routine tests, but expect to have some of them earlier and more often.
Your doctor may suggest that you see a perinatologist, also called a maternal fetal medicine specialist. These doctors are obstetricians who specialize in high-risk pregnancies. They may work with your regular obstetrician to manage your pregnancy and order tests.