Obstetrics Screening Tests
There are many tests available that provide information about your baby’s health. Your doctor will advise you about the most appropriate tests for you. The first tests to consider investigate the baby’s genetic make-up. Screening for genetic problems may involve a blood test (MT21 test or Harmony), or an ultrasound measuring the thickness of the back of the baby’s neck (nuchal translucency). Occasionally, we recommend additional tests such as amniocentesis or chorionic villus sampling. Between 15-18 weeks, we recommend the Alpha-Fetoprotein (AFP) test to determine whether or not there is a problem with the baby’s spinal cord closing. Prenatal vitamins and folic acid supplements have been very successful in reducing this problem.
Amniocentesis is a prenatal screen test where a small amount of amniotic fluid surrounding the fetus is removed for testing. The sample is obtained with a fine needle inserted into the uterus through the abdomen during an ultrasound. It is performed to test for certain types of birth defects such as Down syndrome, sickle cell disease, cystic fibrosis, muscular dystrophy and Tay-Sachs. Because there is a small risk to the mother and baby during the screening, it is usually only recommended for women who have a significant risk for genetic diseases or will be age 35 or older at the time of delivery. A similar test is Chorionic Villus Sampling, which tests cells from the placenta.
Glucose screening tests determine whether or not the mother has developed gestational diabetes. The first, called the Glucose Challenge Screening, is a preliminary blood test performed between 26-28 weeks. If a positive result is obtained with the first test, a second blood test, the Glucose Tolerance Test, may be performed to confirm the diagnosis. Not all women who test positive for the Glucose Challenge Screening test are found to have gestational diabetes upon further evaluation. We ask that you not eat foods that will broken down into sugars the day of your test.
Alpha-Fetoprotein (AFP) Test
AFP is a substance made in the liver of a fetus, and checking AFP levels in the mother’s blood can help us determine if the baby has spina bifida or anencephaly. It can also help determine whether or not the baby has chromosomal problems including Down syndrome or Edwards syndrome. The test can be used to pinpoint congenital difficulties like omphalocele, where some of the baby’s intestines stick out through the belly wall.