Maternal azathioprine therapy and depressed haemopoiesis in the babies of renal allograft patients

Maternal immunosuppression with azathioprine during pregnancy can depress fetal haemopoiesis resulting in neonatal thrombocytopenia and leucopenia with the potential for serious sequelae. The effect on the infant of adjusting azathioprine dosage on the basis of maternal total leucocyte count has been studied in 10 pregnancies in eight renal allograft recipients. Throughout the first six pregnancies azathioprine dosage was unchanged and although the characteristic pregnancy leucocytosis was evident it was not maintained in four patients whose leucocyte counts by 32 weeks gestation were significantly less than our norm [10.3 (SD 1.7) X 10(9)/1] and who subsequently had babies with cord leucocyte counts less than or equal to 8.0 X 10(9)/l, again significantly less than our norm [13.7 (SD 3.9) X 10(9)/l]. A significant correlation existed between maternal leucocyte counts at 32 weeks gestation and at delivery and cord leucocyte count (r = 0.847; P less than 0.01 and r = 0.915; P less than 0.01 respectively). Three of these infants had platelet counts less than or equal to 100 X 10(9)/l but there was no correlation between maternal platelet counts at 32 weeks gestation or at delivery and cord platelet count. For the next four pregnancies policy changed: at 32 weeks gestation azathioprine dosage was halved if maternal leucocyte count was at or below the 1SD band (8.6 X 10(9)/l) for normal pregnancy. All of the infants were haemotologically normal and two patients whose first babies had leucopenia and thrombocytopenia had second babies without problems. Analysis of data from all 10 pregnancies still demonstrated a significant correlation between cord leucocyte count and maternal leucocyte count at delivery but no longer at 32 weeks gestation.(ABSTRACT TRUNCATED AT 250 WORDS)