Amniocentesis is a prenatal test which is designed to identify chromosomal abnormalities in a baby which may lead to birth defects or serious developmental problems. The procedure is recommended for women over 35, since they have a greater risk of having children with chromosomal defects, although any women may request amniocentesis, along with other prenatal tests. There are some risks to amniocentesis which should be considered before embarking on the procedure, and a good doctor will discuss these risks with the patient before beginning. Parents may be asked to sign a form understanding that they acknowledge the risks of amniocentesis before the procedure will be carried out.
When amniocentesis is performed, a needle is interested into the abdomen to collect a small sample of amniotic fluid. The patient may receive a small numbing injection, and the procedure is typically guided by ultrasound to ensure that the doctor knows where he or she is going. The sample of fluid is analyzed, in a process which may take several weeks, depending on which tests were requested. The procedure takes place in the second trimester of pregnancy, typically around 15 weeks. The risks of amniocentesis appear to be greatest in pregnancies of less than 14 weeks.
One of the biggest risks of amniocentesis is miscarriage or pre-term labor. Statistics on this risk vary; many studies carried out in the 1970s, for example, put the risk somewhere around one in 200. However, a study in the United States in 2006 indicated that the risk could be as low as one in 1,600. It appears that more experienced doctors experience a lower miscarriage rate among their patients, and it is an excellent idea to ask a doctor about his or her personal experience with complications and miscarriages.
In some cases, amniocentesis may cause an infection, by introducing bacteria through the needle site into the amniotic sac. This is quite rare, but it can cause pain and cramping, or harm the baby. Another of the risks of amniocentesis is trauma to the baby, which may result in physical deformities. The use of ultrasound greatly reduces this risk, as does working with a competent doctor. Leaking of amniotic fluid can also be a danger; although a small amount of leaking is normal, it should be carefully monitored to ensure that fluid levels do not drop dangerously low.
One of the lesser known risks of amniocentesis is a condition known as Rh incompatibility. Put briefly, this condition represents a conflict in blood type between the fetus and the mother, causing the mother's immune system to attack the fetus as a foreign body. If amniocentesis results in the exchange of blood, as may happen when the placenta is accidentally pricked, it can trigger an Rh response on the part of the mother. Ideally, the risk of Rh compatibility will have already been identified and addressed; there are some preventative measures which can be taken to treat it.