Antenatal fetal blood sampling for the management of alloimmunized pregnancies: effect upon maternal anti-D potency levels.

Increase in maternal anti-D concentrations after intrauterine investigation has been studied retrospectively in 95 rhesus (D) alloimmunized pregnancies; 48 were managed by fetal blood sampling (FBS) procedures (using fetoscopy or ultrasound-guided needle sampling) and 47 using amniocentesis. In those pregnancies where the fetus was rhesus (D) positive, the frequency of procedure-related increases (greater than 50%) in maternal anti-D potency was estimated following single procedures and found to be similar for the two methods of FBS employed (28%) and for amniocentesis (31%). The proportion of pregnancies showing an increase in anti-D potency was higher after ultrasound-guided needle sampling (75%) than after fetoscopic FBS (40%) and after amniocentesis (44%).