Amniocentesis is a procedure in which some of the amniotic fluid surrounding the baby is removed from the mother’s uterus. The amniotic fluid has passed in and out of the baby’s body, and therefore contains some of the baby’s cells. These cells can be read to see if a disease such as Down syndrome, spina bifida, cystic fibrosis, Tay-Sachs, sickle cell anemia, or anencephaly is present.
Why is Amniocenteses Used?
This test is used to obtain information about the baby’s genetic makeup and the potential for genetically inherited diseases. It can also determine the gender of the baby. If there are concerns that the baby will be born prematurely, amniocentesis can determine if the baby’s lungs are mature enough to breathe normally after birth.
How is Amniocentesis Done?
A hollow needle is inserted into the mother’s uterus through her abdomen. A local anesthetic may be used, although discomfort might still be experienced. Ultrasound is conducted before and during the procedure to determine the position of the baby and the placenta to avoid hitting them with the needle. About half an ounce of amniotic fluid is removed. This test should take less than 30 minutes.
If you decide to have amniocentesis, you will need to take the day off. It is done either in a doctor’s office or in a hospital. You will probably be advised to lie down at home after the test and rest. Some practitioners suggest their patients have a glass of wine to relax and to reduce the potential for cramping.
You will most likely get results from the test in two to three weeks. Your practitioner will not reveal the baby’s sex to you unless you specifically ask for this information.
When is Amniocentesis Necessary?
The American College of Obstetricians and Gynecologists (ACOG) now recommends the less invasive triple screen blood test in all pregnancies for women over 35, following up with amniocentesis only if high risk in indicated.
When is Amniocentesis Unnecessary?
Genetic conditions happen to the babies of women of all ages, while genetic accidents, such as Down syndrome, occur more often in the children of older mothers. This is one reason amniocentesis was routinely prescribed for women over 35 until recently. It may be, however, that other age-related factors such as diet, general health, exercise, and exposure to radiation and environmental toxins—rather than age alone—are the real causes of genetic anomalies. That’s why age is not an absolute indicator of risk. You can review questions regarding your own personal risks with your birth attendant.
How Effective is Amniocentesis?
While amniocentesis can diagnose hundreds of diseases and conditions, it is most effective when the laboratory is instructed to look for a specific condition. The procedure has two major disadvantages in terms of acting on this information. It can take two to three weeks for the results to become available, and the procedure is not usually done until the end of the fourth month, when sufficient fluid for testing is available. Culture failure, which occurs in 2 percent of test samples (Murray Enkin et al., A Guide to Effective Care in Pregnancy and Childbirth (New York: Oxford University Press, 2000), 64), can require a repeat sample and therefore prolong final results until well past the middle of the pregnancy.
Is Amniocentesis Safe?
Amniocentesis carries a miscarriage risk of 1 to 3 percent—almost three times the miscarriage rate in a pregnancy where amniocentesis has not been performed. (Murray Enkin et al., A Guide to Effective Care in Pregnancy and Childbirth (New York: Oxford University Press, 2000), 64.). With a more experienced practitioner, the risk may be slightly less. For women whose tests have to be readministered due to culture failure, the risk of miscarriage doubles to 3 to 6 percent.
Studies also show a risk of low-birth-weight infants in about .5 percent of women who have undergone the test, and an increase in respiratory distress syndrome in their infants (Murray Enkin et al., A Guide to Effective Care in Pregnancy and Childbirth (New York: Oxford University Press, 2000), 64.)
Side effects of the procedure itself include cramping, bleeding and leaking of amniotic fluid. These side effects may be quite minor or more severe.