Local anesthesia ineffective for amniocentesis

NEW YORK (Reuters Health) - The pain experienced by pregnant women who undergo amniocentesis is not relieved by injections of lidocaine into the abdominal area, a new study confirms.

Many women assume that a local anesthetic will be given before amniocentesis, Dr. Michael C. Gordon and colleagues point out in the American Journal of Obstetrics and Gynecology. The results of this study, along with those of a previous one, "should be used to explain to women why an anesthetic is not used," they write.

Although usually not the primary reason, fear or concern over the pain associated with amniocentesis is a factor in women's decisions about undergoing the procedure, they point out.

Amniocentesis is performed using a hollow needle that is inserted into the uterus so a small amount of amniotic fluid can be withdrawn from the sac surrounding the fetus.

This diagnosis test, normally recommended for higher risk pregnancies, detects chromosomal disorders, such as Down's syndrome; birth defects, such as spina bifida (failure of the spine to close) and anencephaly (all or part of the brain is missing); and many inherited metabolic disorders.

It may also be performed in late pregnancy to confirm suspected problems such as Rh incompatibility, infection or immature lungs.

In a review of the literature, Gordon, from Wilford Hall U.S. Air Force Medical Center, Lackland Air Force Base, Texas, and colleagues identified only one study that evaluated the effects of local anesthesia during amniocentesis. This study, performed in a group of similar Belgium women, showed no benefit.

Gordon's team also conducted their own study with a diverse group of American women undergoing amniocentesis. One hundred two women received no local anesthesia and 101 received local anesthesia with 1 percent lidocaine. The women were injected just beneath the skin and then received a deeper injection into abdomen.

When the women rated their pain immediately after the procedure, the researchers found no statistically significant differences in the average pain scores between the women who received local anesthesia and those who did not.

Gordon and colleagues suggest it might be worthwhile to see if an anesthetic injected directly into the lining of the uterus could relieve the pain during amniocentesis.

SOURCE: American Journal of Obstetrics and Gynecology, January 2007.