Sample Fetal Scalp in Immune Thrombocytopenia

Sample Fetal Scalp in Immune Thrombocytopenia

Bruce Jancin

VAIL, COLO. — The best way to manage delivery in a woman with immune thrombocytopenia is to get a fetal scalp blood sample during labor, and if a smear doesn’t show platelets, then proceed to cesarean section, Dr. Richard L. Berkowitz recommended.

“The reason I suggest that is because if you vaginally deliver a baby who has a birth platelet count of less than 50,000 /[micro]L and it bleeds into its head, in today’s world it’s going to be very difficult to defend that in court,” he explained at a conference on obstetrics and gynecology sponsored by the University of Colorado.

A plethora of other obstetric management approaches to maternal immune thrombocytopenia have been advocated. In 2001 an obstetrician could probably try any of them and would be able to find experts to support them, said Dr. Berkowitz, professor and chair of the department of ob.gyn. at Mount Sinai School of Medicine, New York.

But he said there are disadvantages to each of these approaches. The alternatives include:

* Performing percutaneous umbilical blood sampling (PUBS) before labor. Third-trimester PUBS presents technical problems because the fetus is much larger than what physicians are accustomed to when performing conventional second-trimester PUBS.

In a series of PUBS done at term in 173 women with immune thrombocytopenia, 2.8% of patients had to undergo an emergency C-section for fetal distress associated with fetal blood sampling.

“You’re doing the PUBS to avoid C-section, right? Well, if your test causes you to do the thing you’re trying to avoid, I think there’s a problem with the test,” he said.

* Screening by looking for antiplatelet antibodies. Contrary to a couple of reports in the 1990s, this turns out not to be an effective way to identify fetuses with thrombocytopenia.

* Ignoring fetal platelet count and performing a C-section only for obstetric indications. While this is the policy today at some medical centers, Dr. Berkowitz said he is “personally uncomfortable” at the thought of delivering a baby with a platelet count below 50,000/[micro]L following a long labor. “And I would definitely not want to put any forceps or a vacuum on such a patient unless I had the reassuring scalp sample,” he added.

It’s an easy matter to obtain the fetal scalp blood sample once the mother is a few centimeters dilated. A Wright’s stain should then be done on the blood smear; often this requires a hematologist’s expertise.

Immune thrombocytopenia is threefold more common among women than men. It is probably the most common autoimmune disorder in pregnancy, affecting 1-3 per 1,000 pregnancies.

“Immune thrombocytopenia is something you’ll definitely see in your practice if you take care of obstetrical patients,” Dr. Berkowitz said.

The disorder results from IgG antibodies attacking maternal platelets, permitting them to be destroyed by the reticuloendothelial system. These maternal antiplatelet antibodies readily cross the placenta. Ten to 20% of neonates whose mother has immune thrombocytopenia have a birth platelet count below 50,00/[micro]L.

He reassured obstetricians that they won’t get hassled by hospital administrators or department heads for performing a cesarean section in those patients having immune thrombocytopenia when platelets can’t be found on a fetal blood smear.

“I give you my word. They’re not going to call you in and say, ‘We’re really concerned about your section rate, Dr. Jones, because you sectioned this lady.’ I just think it’s the smart thing to do,” he added.

COPYRIGHT 2001 International Medical News Group

COPYRIGHT 2001 Gale Group