Fetal blood testing

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Fetal blood testing

Overview

Risks

Results

Fetal blood testing

Definition:

Fetal blood testing is a transvaginal (into the vagina) procedure performed during active labor. The scalp of the fetus is cleansed and pierced, and a small blood sample is taken for evaluation.

Alternative Names:

Fetal scalp blood; Scalp pH testing

How the test is performed:

The procedure typically takes about 5 minutes. The mother is placed in the lithotomy position (on her back with knees and legs pulled toward the chest). 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 is cleansed and dried with long cotton swabs, and a small amount of petroleum jelly is applied so the blood droplets will form beads for easier collection. A small puncture is made in the scalp and blood droplets are 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 is unable to be still, it will be very difficult to perform this test. If her cervix is not dilated enough, it is impossible to perform this test.

How to prepare for the 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 only preparation required is to remain calm, because if the mother is upset it might be difficult to perform the test.

How the test will feel:

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

Why the test is performed:

Usually this test is performed to obtain information about fetal acid-base balance (blood pH). Sometimes fetal heart monitoring doesn't provide enough information about the well-being of a baby. In these cases, testing the scalp pH can help the doctor decide whether the fetus is getting enough oxygen during labor. This helps determine whether the baby is healthy enough to continue labor, or if a forceps delivery or cesarean section might be the best route of delivery.

Although the test is not uncommon, most deliveries do not involve fetal scalp pH testing.

Review Date: 7/19/2004
Reviewed By: Peter Chen, M.D., Department of Obstetrics & Gynecology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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