Fetal blood testing is a transvaginal (into the vagina) procedure performed when a woman is in active labor.

The procedure typically takes about 5 minutes. The mother lies on her back with her feet in stirrups. If her cervix is dilated at least 3 to 4 centimeters, a plastic cone is placed in the vagina and fit snuggly against the scalp of the fetus.

The scalp of the fetus is cleansed and pierced, and a small blood sample is taken for examination. The blood is collected in a thin tube. The tube is either sent to the hospital laboratory or analyzed by a machine in the labor and delivery department. In either case, results are available in just a few minutes.

If the woman's cervix is not dilated enough, it is impossible to perform this test.

The health care provider will explain the procedure and its risks. There isn't always a separate consent form for this procedure because many hospitals consider it part of the general consent form you signed at admission.

The procedure should feel like a long pelvic exam. At this stage of labor, many patients already have had epidural anesthesia and may not feel the pressure of the procedure at all.