Pregnancy, HTLA antibodies and risk of hemolytic disease of the fetus/newborn

The Medical Director of a hospital-based laboratory in Virginia wonders what to advise clinicians about the significance of a high titer low avidity antibody (so called HTLA) that was detected during a woman's third trimester of pregnancy, and who underwent a caesarean section due to intrauterine growth retardation, gestational hypertension and failed induction. The inquiring physician has been unable to find guiding literature to indicate what the relative risk of such an antibody might be to the woman and/or her future pregnancies. He wonders if the HTLA titer offers valuable information, and/or if it would be useful to identify the antibody's exact specificity. Should other serologic testing be performed? Is there a way to predict clinical significance of an HTLA in this setting and thus be able to advise the clinician about the relative risk to future pregnancies?

The following clinical follow up has been provided:

The baby was delivered somewhat small (5 pounds 12 ounces) with Apgars of 7 & 9. The infant required no transfusions.

The work-up to date on the mother shows the following:

1. Group O Rh positive with negative autocontrol
2. Red Cell Phenotype:
   1. Negative for C; Fya; Fyb; S
   2. Positive for c; E; e; Jka; Jkb; s
3. HTLA assessment
   1. Initial antibody screen cell reactions are 1+ using LISS-AHG and 1+ to 3+ using PEG-AHG
   2. The antibody panel shows similar results to the screening cell testing
   3. Phenotypically matched donor red cells react 1+ in a crossmatch.
   4. The patient's HTLA antibody has a titer of 64, it is destroyed by DTT (Dithiothreitol) treatment, and the strength of the reactions are reduced to W+ using Ficin
   5. Samples were sent to the NIH, where they identified the antibody as anti-Hy

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