Hematological effects of zidovudine prophylaxis in newborn infants with and without prenatal exposure to zidovudine.

Postnatal prophylaxis with oral zidovudine (ZDV) is associated with hematological effects. However, it is still unknown whether selection of non-ZDV-based regimens in pregnancy may reduce hematological toxicity associated with postnatal ZDV prophylaxis. The aim of this study was to define the hematological effects of ZDV prophylaxis in newborns with and without prenatal exposure to ZDV. Sixty-five newborns from mothers infected with HIV who, during pregnancy, received HAART regimens with (n:44) and without (n:21) ZDV were evaluated. Virological and hematological data were compared at birth and at 4 weeks and 6 months of life. Newborns with prenatal ZDV exposure had significantly worse hematological values at birth, with lower levels of hemoglobin (14.3 g/dl vs. 16.2 g/dl, P=0.001), red blood cell count (3.45 × 10(6) cells/mm(3) vs. 4.48 × 10(6) cells/mm(3), P<0.001), and hematocrit (41.0% vs. 46.8%, P<0.001), and higher values of mean corpuscular volume (119 fl vs. 103 fl, P<0.001). The start of ZDV prophylaxis determined significantly greater adverse hematological changes in newborns without prenatal ZDV exposure, and at 4 weeks and 6 months of life the two groups had substantially identical hematological values. The selection of non-ZDV-based regimens in pregnancy does not reduce the final hematological effects of postnatal ZDV at 4 weeks and at 6 months of life. However, two distinct pathways may be observed: newborns exposed prenatally to ZDV have worse hematological values at birth, while newborns without prenatal ZDV exposure have particularly marked postnatal effects. The distinct effects of these two pathways should be considered.