How the Test is Performed

You will be placed in the lithotomy position (on your back with knees and legs pulled towards your chest). If your cervix is already dilated at least 3 to 4 centimeters, then a plastic cone is placed in the vagina and snugged up 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 to the scalp so fetal blood droplets will form beads and ease collection. A small puncture is made in the scalp and fetal blood droplets are collected in a thin glass tube. The tube is either sent to the hospital lab or analyzed by a machine on the labor floor. In either case, results are available in just a few minutes.

If you are unable to be still, it will be very difficult to perform this test. If your cervix is not dilated enough, then it is impossible to perform this test. The procedure typically takes about 5 minutes.

How to Prepare for the Test

Your health care provider explains 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 you are 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. They might 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 the fetal heart tracing doesn't give your doctor enough information about the well being of your baby. In these cases, testing the scalp pH can help your doctor decide if your fetus is getting enough oxygen during labor. This helps determine if your 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 pregnancies will not need to undergo fetal scalp pH testing.

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