Second trimester amniocentesis in twin pregnancies: maternal haemoglobin as a dye marker to differentiate diamniotic twins.

Objective: To review the use of a membrane-free haemolysate prepared from maternal blood to distinguish the amniotic sacs at amniocentesis in twin gestation.
Setting: University Hospital, Groningen.
Method: Haemoglobin solution prepared from maternal blood.
Subjects: 63 twin pregnancies having amniocentesis.
Results: The fetal loss before 28 weeks was 4%. There was no perinatal mortality. Dye was detected in the second sac in 9 of 24 women tested before 1985 and none of the 39 women since, no malformations could be ascribed to the use of the haemolysate.
Conclusion: The use of the membrane-free haemolysate is safe, but the technique will probably gradually become redundant because of improved ultrasound.