because women over age 35 are more likely to have certain problems during pregnancy the following tests may be recommended. these tests can help detect disorders before during and after your pregnancy. some of these tests require appropriate genetic counseling including a detailed discussion regarding the risks and benefits of the procedure(s). whether you choose to have the tests is up to you. talk to your health care provider to find out if any of these tests are right for you. ultrasound: a test in which high-frequency sound waves are used to produce an image of your baby. ultrasound is used early in pregnancy to determine viability (if the baby is in the uterus and if the baby's heart is beating) the presence of more than one fetus and to determine your baby's due date or gestational age (the age of the fetus). later in pregnancy ultrasound may be used to see how the baby is doing to determine placenta location and the amount of amniotic fluid around the baby. quad marker screen: a blood test in which substances in the blood sample are measured to screen for problems in the development of the fetus' brain spinal cord and other neural tissues of the central nervous system (neural tube) such as spina bifida or anencephaly. neural tube defects occur in 1 or 2 out of every 1 000 births. the quad marker screen can detect approximately 75% to 80% of open neural tube defects. the quad marker screen can also detect genetic disorders such as down syndrome a chromosomal abnormality. the quad marker screen can detect approximately 75% of down syndrome cases in women under age 35 and over 80% of down syndrome cases in women age 35 years and older. it is important to note that a "positive” result from this blood test is not definitive for a birth defect. usually the next step is to offer the mother an amniocentesis to evaluate the baby’s chromosomes as well as an ultrasound to evaluate the baby’s body for signs of birth defects. the quad marker screen may be performed between the 15th and 20th weeks of pregnancy. first trimester screen: a newer test done between weeks 10 to 14 detects the presence of two markers in a blood sample in conjunction with an ultrasound to measure the thickness of the back of the fetus' neck. it tests for chromosomal abnormalities like down syndrome. it is essentially as accurate as the quad marker screen but results can be obtained earlier in the pregnancy. amniocentesis: amniocentesis also called an amnio is a procedure in which a small amount of amniotic fluid is removed from the sac surrounding the fetus and tested for birth defects. while it does not detect all birth defects it can be used to detect sickle cell disease cystic fibrosis muscular dystrophy tay-sachs disease or down syndrome if the parents have a significant genetic risk. amniocentesis can also detect certain neural tube defects (where the spinal cord or brain don't develop normally) such as spina bifida and anencephaly. because ultrasound is performed at the time of amniocentesis it may detect birth defects that are not detected by amniocentesis (such as cleft palate cleft lip club foot or heart defects). there are some birth defects however that will not be detected by either amniocentesis or ultrasound. chorionic villus sampling (cvs): a test in which a small sample of cells (called chorionic villi) is taken from the placenta where it attaches to the wall of the uterus. chorionic villi are tiny parts of the placenta that are formed from the fertilized egg so they have the same genes as the fetus. if you have certain risk factors you may be offered cvs as a way to detect birth defects during early pregnancy. cvs requires appropriate genetic counseling including a detailed discussion regarding the risks and benefits of the procedure.
what types of prenatal tests should i have if i become pregnant after age 35?