Survival analysis of transfused fetuses affected by Rh-alloimmunization

The aim of the present study was to evaluate the survival rate of a group of 86 fetuses affected by Rh-alloimmunization submitted to intrauterine red blood cell transfusion. All the women had antibody titres> or = 1:32 at the time of their enrollment in the study. Crude fetal survival rate was 89.5% (77/86 cases). Data were stratified according to specific cut-off points of (1) pre-transfusion fetal haemoglobin expressed as the rate between the observed and the estimated value for each gestational age at the time of the first transfusion; (2) the difference between the haemoglobin at the beginning of the second-transfusion less that at the end of the first transfusion (delta haemoglobin); and (3) presence of ultrasound detected anomalies. Statistically significant stratification of the survival rate was observed for the level of pre-transfusion fetal haemoglobin (95% and 76.9%, respectively, p= 0.009) using a cut-off value of < 70% and > or = 70% of the expected value. Again, delta haemoglobin showed a different survival rate when a cut-off value of 6 g/dl was used to generate subgroups of fetuses: 94.6% and 80%, respectively (p= 0.0145). Among the ultrasound anomalies, the presence of hydrops showed a correlation with the survival rates. The quoted values were 97.83% (absence) and 80.0% (presence) respectively (p= 0.0058). Cox regression showed a significant association of the studied variables with the outcome (survival). The presence of hydrops was the best predictor (Odds ratio= 8.7, p= 0.0073) followed by Delta haemoglobin (Odds ratio= 2.0, p= 0.0422). The rate of pre-treatment fetal haemoglobin < 70% of the expected value did not add any significant valu and was thus removed from the final model. Weight at delivery expressed in grams showed a direct correlation with the survival rate (Odds ratio= 0.9, p= 0.1529) and was added into the model as an adjustment quantitative variable.