Locked twins (Hebrew)

Locked twins occur in 1 out of 70,000 to 90,000 births or 1 out of 817 twin pregnancies. However, if we consider this condition to include all pregnancies in which the twins lie parallel in the vertical axis of the uterus with their poles in opposite directions and the first twin in breech presentation, the incidence is 1 in 87. The four types of locking are: collision, impaction, compaction and interlocking. The risk is greatest when locking occurs at or below the pelvic inlet, when the fetal mortality is 50%, with the first twin most often affected. Predisposing factors to locking are low fetal weight, a young primipara mother, large maternal pelvis, paucity of amniotic fluid, premature rupture of the membranes, increased tonicity of the uterus and the use of oxytocic drugs. Early diagnosis of potential locking is based on anteroposterior and lateral X rays. When diagnosed early, the treatment of choice to assure the lives of both twins is Caesarean section. However, when there is locking at or below the pelvic inlet and the first twin has been partially born in breech presentation, attempts should be made either to push the head of the second twin above the pelvic inlet, to deliver both of the heads together using forceps, or to deliver the second twin first. One author recommends immediate Caesarian section to save at least the second twin. In case of death of the first twin the treatment of choice is decapitation or craniotomy and then vaginal delivery of the second twin in the usual manner. Two cases of locking below the pelvic inlet (compaction) out of a total of 18,369 deliveries are presented.