Peace at last

The consult with Dr. C last week seemed finally like the answer to our prayers. It didn't answer all of our questions, but at least we finally feel like we talked directly to someone who knew what he was talking about.

We don't have a different answer than before, but I now feel peace about it. I am not in a state of desperate panic about not seeking preventative treatment for this pregnancy. I don't feel quite so much like a ticking time bomb. I do still have some anxiety about whether to pursue a cordocentesis in the 8th month, and whether to plan a C-section, but that isn't a decision that needs to be made now, so there really is nothing more to do, and I can put it from my mind a bit. That is a good feeling.

A recap of our conversation with Dr. C (quotations are not exact but based on my notes):

How is the antibody testing done?
Jennifer's serum is mixed with a random platelet sample. The lab looks for platelet aggregation. It won't show up if the antibodies are present at a low level or a low intensity, which is what I am calling the non-specific immune response, as I suspect in your case. If the blood has antibodies against very common platelet antigens then you are much more likely to have trouble in this or any subsequent pregnancy.

What was John's actual history?
His platelets counts were

• 40-60,000 at birth on 6/26.
• 30,000 when readmitted to the hospital on 7/3
• 13,000 by 7/5
• He had IVIg on 7/4 and 7/5 (plus steroids)
• 84,000 on 7/6 when he was discharged.

At what platelet level do you consider the switch to be from "low" to "dangerous?"
Right around 50,000

What else could cause low platelet count in an infant besides NAIT (or NATP, the alternate acronym for the same condition that Dr. C preferred to use)?

• infection (unlikely for John - no other clinical signs, which is why they stopped an IV antibiotic treatment on 7/4)
• stress at birth ... low oxygen levels during birth lead to decreased blood pH and acidosis (typically would be seen in first 3 days after birth, so again, unlikely in John's case)

Some doctors have indicated that John's records are inconsistent with NAIT, because his levels continued to drop after his birth for 10 days, instead of improving upon birth. Do you have thoughts about whether he really had NAIT?
NAIT involves a highly specific or high intensity antibody. I believe that John's case was  an immune-mediated thrombocytopenia, but not NAIT (the alloimmune variety).  I believe John's case was a non-specific immune-mediated response.

With NAIT, the high-intensity, specific antibodies cross the placenta during pregnancy (which leads to the high prenatal risk to the baby). The non-specific antibodies generally don't cause severe problems prenatally, either because they are present at too low of a level or too low of an intensity. It is believed that newborns may get this non-specific antibody from a direct mixing of mom's and baby's blood, and thus a higher exposure to mom's blood, in the birthing process. Thus, the baby's condition can worsen after birth (the most significant antibody exposure) rather than improve quickly (because no longer getting large doses across the placenta, as with NAIT).

In addition, John's condition may have been exacerbated (though unlikely to have been caused) by the tegretol Jennifer was taking. Low platelet count is a potential side-effect of that medication.

What are your recommendations for this current pregnancy?
First, a non-specific immune response, as I suspect John's case was, means that it is not likely to get worse with each pregnancy (as it would be with NAIT).

Second, probably not useful to keep testing for platelet antibodies in Jennifer's blood during this pregnancy. You didn't have them with John's case (meaning either that they are something that we don't know how to test for, or they weren't there, or they were non-specific enough that they didn't show up in our current screening protocols. Thus, they are unlikely to show up again in this pregnancy, and we have confirmed that already with one screening at 20 weeks. Platelet antibodies last about 6 months to a year, so any that you had from John would be gone by now.

An early delivery will probably not be necessary, unless there were a known event that would cause significant mixing of mom's and baby's blood (like placenta previa).

I concur with recommendation of Dr. Berkowitz, that you either plan a C-section to be safe, or else a cordocentesis to check the baby's platelet levels at 36-37 weeks. If the count is below 50,000, then I would recommend proceeding to an early C-section, probably after allowing about 48 hours on the medication to mature the baby's lungs. If the count is above 100,000, you could plan a normal vaginal delivery.

[Of course, as Jennifer's regular OB, Dr. R, pointed out with her typical good humor at the next visit, "Jennifer, of course you will get a count in between 50,000 and 100,000 and then we'll have to figure out what to do with that."]