Endogenous digoxin-like immunoreactivity during pregnancy and at birth.

1. We have measured endogenous digoxin-like immunoreactivity (EDLI), in mothers and infants, during normal/pathological pregnancies and at birth. 2. During pregnancy, EDLI was measured in 38 maternal-fetal pairs. At the time of fetal sampling, maternal age was 29 (s.d. 6) years and gestational age was 28 (s.d. 6) weeks. EDLI was present in 13 (34%) mothers and in 27 (71%) fetuses. There was no correlation between maternal and fetal concentrations or between maternal or fetal concentrations and gestational age. 3. EDLI was measured at birth in blood samples from 45 maternal-cord pairs. Maternal age was 29 (s.d. 5) years and gestational age was 39 (s.d. 2) weeks. EDLI was present in 11 (22%) maternal and in 44 (98%) cord samples. The concentrations were significantly higher in cord than in fetal or maternal samples (P < 0.001 in both cases). 4. High cord EDLI concentrations suggest acute synthesis during delivery. Thus, the placental transfer of digoxin calculated from maternal and cord digoxin concentrations at birth may be overestimated.